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From sea to source Guidance for the restoration of fish migration in European Rivers



Preface Anthropogenic activities place great demands on the

tion and improvement of our fish resources and fish-

natural environment. Impacts on our aquatic fluvial

eries. As part of this we need to promote the sharing

systems are many and they threaten the bio-diver-

of knowledge on fish migration issues, the challenges

sity and sustainability of flora and fauna including our

we all face and the means of resolving them.

fish populations. Development, construction and infra-structure projects associated with power supply,

We need to continually raise awareness of fish mi-

abstractions, waste disposal, transport, navigation,

gration issues with policy makers and regulators in

recreation and both rural and urban land-use can

national and regional organisations in both the pub-

all have profound and synergistic effects on our river

lic and private sectors, with river managers, with

systems and their inhabitants. So far as fish are con-

stakeholders and with all whose activities affect the

cerned obstructions that interrupt the river continuum

environmental quality of our river corridors. The aim

have marked effects on the ability of fish to migrate

should be to deliver a continually increasing pace of

both upstream and downstream, freely and in safety.

change to remove constraints by eradicating unnecessary obstructions and by mitigating the effects of

The last two decades have seen a great increase in

those that must remain by use of effective upstream

awareness of the need for all species of fish to migrate

and downstream fish ways to promote and protect

in order to fulfil successful life cycles. Gone are the days

freedom of movement.

when only the movements of the major diadromous migrators was recognised and the need for free move-

Professionals working in any field aspire to see best

ment of even the smallest potadromous fish are now

practices adopted and increasingly this is also impor-

more readily acknowledged. The last half of the twen-

tant not just among the practitioners but also among

tieth century saw great improvements in water quality

the broader populace. This non-technical guidance

in many countries and the removal of this constraint has

is intended to be an introduction to the challenges,

further highlighted the part played by barriers to migra-

themes and concepts involved in promoting the free-

tion in restricting fish populations. In parallel with this

dom of movement of fish in the river continuum. It is

has been the apparent decline and struggles of some of

aimed not only at fisheries professionals but also at

our major migrators, such as sturgeon, shad, salmon,

all who exert influence and have an interest in the

sea trout and eel.

riverine environment. It highlights good practices and, for those who must put aspirations into practice,

All of the major migratory fish species are shared by all,

it directs the reader to sources of technically detailed

or most, of the European countries. A large number

guidelines for the constructions of fish passes and

of the other species are common to multiple Euro-

related facilities.

pean States. Pan-European organisations such as EIFAC and ICES play their part in co-ordinating the

Greg Armstrong

management of fish stocks and particularly those of

National Fish Pass Officer

endangered species. The European Water Frame-

Environment Agency, England

work Directive sets new targets for the health and sustainability of our aquatic environment. It is in the common interest of all European countries to communicate and work together to encourage the formation and achievement of common goals for the preserva-


Partners Community Rivers The migratory fish that inhabit our waters are; the

otters (Lutra lutra). They arrive as elvers, in the spring

Atlantic salmon (Salmo salar); the sea trout or sewin

and live for many years in our rivers before returning

(Salmo truta); eel (Anguilla anguilla); allis shad (Alosa

to the Sargasso Sea, in the Atlantic, to breed and die.

alosa) and the twaite Shad (Alosa fallax). The shads

All these fish require clean unpolluted water systems

are rare, protected members of the herring family

and rivers which allow them unrestricted access to

which inhabit the coastal waters around our larger

areas where they breed and grow. Keep Wales Tidy

estuaries and migrate into the lower reaches of three

volunteers assist fish migration through creation

of our rivers to spawn each autumn. The allis shad is

of fish passes, removal of obstructions, bank side

believed to be almost locally extinct.

management and invertebrate monitoring. Many of our dedicated voluntary groups believe the Fish

The salmon spend a large part of their adult life in

Migration Guidance will be of use to them by giving

the sea, migrating to the north Atlantic. On reaching

the opportunity to share ideas and learn how other

maturity they return to the original river, where they

countries deal with similar problems.

were hatched and travel as far upstream as they Pam Barns, Keep Wales Tidy, Wales

can to breed. The sea trout or sewin has a similar life cycle but spends most of its adult life in the sea around our coasts, often returning to their home rivers several times to spawn. Both species of these fish are of great economic value. They are caught both commercially and recreationally and a large angling tourist industry is developed around them. The eels inhabit all our river systems but are of little commercial value in Wales. They do however form a valuable food source for other animals and birds and are known to be a favoured by

Voor u ligt het handboek “From sea to source”. Het

thema’s. Via Community Rivers is deskundigheid uit

eerste Europese handboek over het thema vismigra-

heel Europa bijeengebracht. De kennisuitwisseling

tie. Dit handboek is voortgekomen uit het Europese

die op deze wijze tot stand is gekomen levert met dit

project Community Rivers, een samenwerking tussen

handboek een fraai resultaat op. Dank gaat uit naar

waterbeheerders uit europa die kennisuitwisseling en

de cofinanciers die hebben bijgedragen aan de tot-

burgerparticipatie stimuleert. Waterschap Hunze en

standkoming van dit handboek. Ik hoop dat u, net als

Aa’s is binnen Community Rivers de trekker van het

ik, bij het lezen van dit handboek geïnspireerd wordt

thema vismigratie. Het verheugt mij bijzonder dat

om het herstel van vismigratie van bron tot monding

juist over dit thema een handboek tot stand is ge-

aan te pakken.

komen dat niet alleen ingaat op de technische kanten van de mogelijkheden voor verbeterde migratie van

Prof. mr. Alfred van Hall, dijkgraaf Waterschap

vissen, maar juist ook op de middelen als educatie,

Hunze en Aa’s, Nederland

communicatie en andere, minstens zo belangrijke


“In the town where I was born / Lived a man who

Rius Mediterranis (Museu Industrial del Ter) ha fet

sailed to sea / And he told us of his life / In the land

una catalogació dels dispositius de pas per a peixos

of submarines / So we sailed up to the sun / Till we

i un mapa sobre els graus de connectivitat per als

found the sea of green / And we lived beneath the

peixos als rius de Catalunya per a l’Agència Catalana

waves / In our yellow submarine”

de l’Aigua (Water Catalan Agency). Alhora, el CERM

(McCartney/Lennon, 1968)

ha començat a fer un seguiment de l’eficàcia de diversos d’aquests dispositius de pas.

A la vila on vaig néixer vivia un peix que venia de la mar: l’anguila. Ara no hi és. Als anys seixanta, quan

No hi ha més de cinquanta dispositius de pas per

pacifistes i ecologistes sorgien arreu del món a Ca-

a peixos al conjunt de Catalunya enfront d’un miler

talunya un gran creixement econòmic va portar a la

d’obstacles. La majoria encara comporten grans

construcció de grans embassaments i a la millora de

dificultats per a la migració dels peixos. A les parts

moltes rescloses. Això va tallar la majoria dels movi-

baixes dels rius catalans hi ha una pesca intensiva

ments dels peixos.

de l’anguila, damunt dels adunts però especialment els alevins, les angules. Els estocs d’anguila disminu-

L’anguila (Anguilla anguilla), l’espècie migratòria més

eixen any rere any. D’altra banda, la contaminació i

important de Catalunya, va esdevenir realment en

l’eutrofització de l’aigua estan disminuint.

perill d’extinció. Dissortadament, no està sola: altres espècies tenen problemes similars: la guerxa (Alosa

Ara, l’administració mediambiental catalana segueix

fallax), l’esturió (Acipenser sturio) (probablement ja

la Directiva Marc sobre l’Aigua (2000/60/CE) i per

extingit), la llamprea de mar (Petromizon marinus),

això promou la implementació de solucions reals a

etc. D’altra banda, a Catalunya tenim altres peixos

tot el país, un programa de mesures per assolir-hi el

endèmics valuosos: el barb de muntanya (Barbus

bon estat ecològic en una dècada. Estem segurs que

meridionalis), el barb cua-roig (Barbus haasi), la

aquest manual en serà una eina molt important. Espe-

madrilla (Chondrostoma miegii), la bagra (Squalius

rem que l’anguila salpi altra vegada de tot arreu cap al

cephalus)... I el coneixement de l’ecologia dels peixos

sol fins a trobar la mar verda (dels Sargasses)…

ibèrics és encara incomplerta. Marc Ordeix, CERM,Center for the Study of MePer sort, hem canviat la tendència i ja s’ha iniciat un

diterranean Rivers, Industrial Museum of the Ter

primer pas per millorar la connectivitat per als peixos

River, Manlleu, Catalonia (Spain).

als rius. L’any 2006, el CERM, Centre d’Estudis dels

Řeky tvoří odnepaměti přirozenou osu naší krajiny.

na překonávaní překážek přerušujících plynulý

Podél řek postupovalo první osídlení, po jejich

tok řek, stejně důležité je propojení řeky s její

břehu vedly cesty propojující odlehlé samoty i

údolní nivou, vytváření různorodého a bohatého

velká města. Neúměrná zátěž hospodářského

vodního prostředí pro život ryb a v neposlední

využití se ale musela časem projevit, stejně

řadě podmínek pro jejich přirozenou reprodukci.

jako člověka sužují civilizační choroby, začaly se

Naším cílem tedy nesmí být pouze vlastní rybí mi-

ucpávat i tyto „vodní žíly“ krajiny a příroda trpí

grace, jako prázdný pojem patřící do moderního

nemocí oběhového systému. Obnova migrace

slovníku, ale vytvoření pestrého, silného a geneticky

ryb je sice jen jedním z léků na tuto chorobu,

původního rybího společenstva prosperujícího ve

ale velmi důležitým, neboť ryby stojí na vrcholu

zdravém prostředí našich řek.







poskytují dobrou informaci o celkovém stavu

Ing. David Veselý, Povodí Moravy, Czech Republic

ekosystému. Nesmíme se však soustředit pouze


Rivers of Europe


Contents Preface Rivers of Europe Contents

03 06 07

1. Introduction 1.1 Why an European guidance? 1.2 How to use the guidance 1.3 Community Rivers 2. Fish migration in river systems

3. Policy, legislation and financing

2.1 2.2 2.3 2.4

General characteristics of the European river systems Ecology of rivers and streams Impacts of barriers on fish migration Impact of commercial fisheries

3.1 Policy and legislation 3.2 Funds for fish

4. River basin approach 4.1 4.2 4.3 4.4 5. Solutions for hazards and obstacles

Introduction Ambitions Priority approach Priorities of measures

5.1 Fish migration facilities; status quo 5.2 Fish pass design and construction; a three-step approach 5.3 Step 1: Definition 5.4 Step 2: Design 5.5 Step 3: Construction and maintenance

6. Monitoring and evaluation 6.1 Evaluation of the fish pass 6.2 Choice of monitoring methods 6.3 Aspects of evaluation in practice 7. Communication and education

7.1 7.2 7.3 7.4

Exchange of information Communication with participating organisations Communication with members of the public Education

Literature and bibliography Appendixes Colophon

09 10 11 12 13 14 14 19 23 27 28 33 37 38 39 39 42 49 54 59 62 81 87 91 92 94 99 103 104 106 108 108 111 115 119



1. Introduction Europe consist of 52 countries and, with about 750 million inhabitants, it is the most densely populated part of the world. Although every country has it own unique characteristics, all countries are facing similar problems with respect to fish migration. Targets are the same for all European countries, as defined by the Water Framework Directive. We believe that the countries of Europe should work together closely on fish migration matters, exchanging knowledge for mutual benefit. This practical guidance proposes a first step.


1.1 WHY AN EUROPEAN GUIDANCE? In many European countries there is growing awareness that past management of water systems has not always been optimal for all relevant uses. During the last few decades many natural waterways, including rivers and brooks have been manipulated and managed to improve the regulation of water levels. These improved water systems have often shown great benefits for the local population. During dry summers there has been enough water to irrigate crops and to provide drinking water and in periods of high rainfall it has been easier to get rid of surplus water. In seeking to ensure an optimal use of available water resources, many natural waterways were canalised and weirs, locks and dams were constructed to improve navigation. However the great benefits for water level management and drinking water supplies also had a negative side. As a result of these large scale adaptations the ecological quality of many river systems declined quite dramatically. In many places special river habitats were damaged causing many animal and plant species to disappear locally.

of the knowledge and experience developed through design of fish passes is available in several technical manuals that are available for specialists throughout Europe. Any programme to construct technical fish passes should be supported by a good management plan that demonstrates the benefits and necessity for the proposed measures. Only with a good and integral plan is it possible to justify political and financial support to solve the problems that we face. Within Europe there is a lot of experience in preparing and communicating such fish migration plans, but unfortunately this knowledge is not easily accessible. With this guidance we are seeking to resolve this problem by providing an overview of the latest European developments in solving fish migration problems. This guidance will address the following questions: • How can a vision for fish migration, based on a regional water system approach, be developed? • How can we communicate the necessity and benefits of improving fish migration to politicians and the public in order to raise awareness for the measures that need to be carried out? • How can we integrate fish migration in water management policies (contributing to combined action plans with other opportunities and interests?). • What is the process for the design of an optimal fish pass? • What monitoring techniques are available for studying fish migration and what is the potential to use results for further improvement of fish pass design?

Through implementation of the European Water Framework Directive, the growing belief of Europeans that a further decline of our water systems is unacceptable has now been put into policy. A further loss of ecological quality within European rivers is not acceptable, and where opportunity and potential can be demonstrated countries will now start to prepare plans to restore these systems. Fish are an important part of the ecology in river systems. Many species have declined in numbers or are even extinct regionally or nationally as a result of the loss of habitat and the many man-made barriers to migration in the rivers. Fortunately however, the picture is not bad everywhere. In many countries a lot of work has been carried out to restore river habitats and to solve migration problems by constructing fish passes at weirs and dams. A lot

In order to answer these questions we have sought available knowledge by asking a large number of European experts to fill out a questionnaire. The results of the questionnaire have been used within the chapters of this guidance.


We received information from the following countries: The United Kingdom, The Netherlands, Greece, Switzerland, Portugal, Spain, Catalonia, Austria, Greece, Italy, Lithuania, France, Czech Republic, Hungary, Luxembourg, Germany, France, Belgium, Denmark, Sweden and Finland.

the use of fish passes to provide access to habitat. The guidance does not comment on matters of water quality or the quality of the habitat that might actually be the most important issues for migration in some cases.

1.2 HOW TO USE THE GUIDANCE This guidance provides guidance for restoration of upstream and downstream fish migration in European river systems. The approach comprises a total methodology that gives guidelines on the principles of fish migration in river systems and the implementation of policy and which follows a river basin approach by selecting appropriate solutions for hazards and obstacles. It also considers the maintenance, monitoring and evaluation of facilities and communication and education. This concept can be visualised as a circle in figure 1.1.

Photo: Watermill in the river Geul, The Netherlands.


River basin approach


ing or nit ce mo an s, ten ion in lut ma So and

National and local policy When the generic problems for fish migration have been recognised and agreed, they should be incorporated into appropriate policy. On a European and national level, some legislation already exists and this can have an umbrella function for national policy (e.g. Water Framework Directive).



na po l and lic y loca

Fishmigration in rivers


River Basin Approach Best outcomes are obtained when action plans for restoration of fish migration are set out within a framework for the whole river basin. A plan should comprise ambitions, objectives and targets for priority waters and solutions for obstacles set out in a defined timescale. More locally it will be necessary to use and to influence existing planning and policy procedures.

Figure 1.1 Schematic overview of relevant fish migration issues.

Fish migration in river systems The basic principles of fish migration are presented. This can form the basis of the statement of need for a whole-river management plan for fish migration. The fish migration issues covered in this guidance are all about


Fish passes: solutions, monitoring and maintenance Every fish passage proposal is unique and therefore solutions should be chosen that take into account all relevant factors (including target species, hydraulic conditions etc.). The range of fish pass options available is quite diverse and general design guidelines should be used to generate an optimal solution. The construction programme itself needs to be addressed as a process in which hydraulic engineers, biologists and the construction contractor work closely together. Future fish pass monitoring and maintenance also needs to be part of the plan. Technical data on solutions or monitoring can be found in the reference list.

The Community Rivers project aims to stimulate knowledge exchange on the following four themes: • Education with regard to river- and watermanagement; • Active participation of local organisations and the public in the planning and management of rivers; • Restoration of river systems; • Fish migration in river systems.

Communication and education The outer layer of the circle represents communication and education. This is an important part that should always be incorporated in the process. Communication between experts, organisations and members of the public ensures exchange of best practice and a raised profile of the work. This complements education which can inform the public, from children up to experts, of the need for effective facilities to promote fish migration and their future maintenance. 1.3 COMMUNITY RIVERS This guidance is a product of the Community Rivers project, the aims of which have been the exchange of knowledge on durable river management and the active participation of local authorities, organisations and the public. The partners of the project, which started in 2004 and which will finish in 2007, are: • Torfaen County Borough (lead partner), Wales (United Kingdom); • Keep Wales Tidy, Wales (United Kingdom); • Southern Moravia Region, Czech Republic; • Hunze and Aa’s Water Board, The Netherlands; • Centre d’ Estudis dels Rius Mediterranis (MIT Foundation), Catalonia (Spain); • Parc fluvial Navàs-Berga, Catalonia (Spain).

Photo: The river Ter in Catalonia is an important river for fish migration.


2. Fish migration in river systems Alterations of the aquatic environment, changes in land use and exploitation of fish stocks have led to the decline of species diversity and disappearance of several species in Europe. Some species are endangered on a national level and some species are endangered or even extinct on a continental level. Recruitment of European eel (Anguilla anguilla) has declined over most of the continent since the early 1980’s, to about 10% of former levels, with the lowest values recorded in 2001 (Dekker [ed.], 2002). Atlantic Sturgeon (Acipenser sturio) has suffered a stock decline and extinction in Northern Europe since the first half of the 20th century and in the rivers Gironde (France) and Rioni (Georgia) the last two populations are also threatened by extinction. The anadromous and potamodromous sturgeon species from the Danube river basin and the Black Sea are also currently endangered.


A good understanding of fish biology and migration is an important basis to make the right decisions for the future of fish migration in our rivers. The knowledge required covers the species that undertake migration, the timing of their seasonal migration, the desired habitats, the characteristics of rivers and anthropogenic impacts on the river and consequences for fish migration. This chapter discusses the characteristics of natural river systems and the need for fish migration, human impacts on rivers and the consequences of these for fish, and the current state of the art solutions for fish passage, all with respect to the pan-European situation.

Europe the annual snow melt causes high water levels during the spring which follows a period of ice coverage. The southern European rivers carry relatively small amounts of water during the summer period and some, for example in Spain, completely dry up. Europe contains relatively few lakes, although the historically icecovered areas of Scandinavia and the Alpine areas are rich in lakes. Lakes are particularly prevalent in Finland and includes Lake Ladoga, the largest lake in Europe. 2.2 ECOLOGY OF RIVERS AND STREAMS 2.2.1 Hydrology Rivers typically originate in upland areas from springs and rivulets that combine to form fast flowing shallow streams. These in turn join with other tributaries to form larger, more smoothly flowing and deeper rivers that meander through lowlands into the sea. The discharge of rivers depends on the amount of rainfall that finds its way into streams and then leaves the catchments as stream flow. This varies with geography. Seasonal influences on discharge lead to characteristic patterns of flows in different parts of Europe. Some rivers show great fluctuations in flow, whilst others have an almost constant flow throughout the year. Some streams show seasonally predictable flows, whilst others have an irregular flow pattern.

Photo: The River Lamprey is a typical migrating fish specie.

2.1 GENERAL CHARACTERISTICS OF THE EUROPEAN RIVER SYSTEMS Europe comprises two major drainage areas. The big continental watershed divides the North West, descending to the Atlantic Ocean and its connecting seas, from an area that drains to the Mediterranean, Black and Caspian seas. This results in very large river systems in south Eastern Europe, for example the rivers Volga and the Danube, several of which drain into inland seas or into the Arctic Ocean. Rivers of Western Europe have their upper reaches mostly in mountainous or upland areas whereas the rivers of Eastern Europe flow through lowlands and, in contrast, are characterised by calm flowing and easier navigable waters in which pool and riffle structures are scarce. The water drainage and discharge patterns in Western Europe are relatively constant, consisting of seasonally high water levels in spring and autumn with infrequent ice coverage. In central and eastern

Across Europe the structure and function of rivers varies widely. In arid and Mediterranean climates many streams dry up, sometimes for a period of several months and consequently the fauna is often limited and dominated by species that are generalist or adapted to temporal survival. These and other dry river channels usually have relatively unvegetated banks due to the limited opportunity for establishment of riparian plants. In contrast, large and permanent rivers often support high riparian and aquatic species diversity. As a consequence of rainfall or snow melt they have lateral floodplains that are formed outside the normal riverbed and supplied by seasonal floods. These floodplains


are characterised by a high degree of lateral processes and the organisms of floodplain rivers are adapted to changes in discharge and flooding. Fish use inundated areas for foraging, spawning and as nursery areas and free movement between these habitats is an important requirement. Floodplains differ substantially in size, the largest in Europe being the River Danube, only fragments of which now remain.

running waters outside Europe. This is based on the physical structures of the river bed and the water temperature that prevails during the year. The running waters are divided into brooks (rhitron) and rivers (potamon) and can be further divided into upper, middle and lower reaches. For central European waters, indicator fish zones are synonymous with the classification of Huet (1949).

2.2.2 Biological zoning The distribution of fish species varies according to different physical properties of the watercourse. Different fish species are bound to particular river stretches and the taxa of these species have been used to provide names for typical reaches of the streams. Based on physical parameters such as the slope, width and water temperature, stream sections are divided into trout, grayling, barbel and breamruffe zones (Huet, 1949). This classification is suitable for streams in northwest Europe and the Carpathian area of Central Europe. In the rivers and streams of the British Isles this zonation is not as fully developed because the watercourses are in general shorter from sea to source. Illies (1961) suggested a classification that fits all aquatic fauna and can also be applied to

2.2.3 Migration of freshwater fish Fish migration is a well known phenomenon and occurs for different purposes. The distance of migration varies between species, within populations of the same species or even within one population of a species. There are also different types of fish migration. Some migrations involve movement of fish between freshwater and the marine environment and can involve distances of thousands of miles and prolonged residence in both habitat types. More typical is the ‘seasonal movement’ of fish in order to move between necessary habitats, for example between winter refuges and spawning or nursery habitats. Other migrations are on a smaller scale, for example ‘daily movements’. These occur in all habitats as fish move between refuges and feeding areas.

Figure 2.1: Schematic illustration of lateral and longitudinal migration between refuge, feeding and spawning habitats of fish.

Interruption of migration connectivity owing to barriers formed by weirs or dams, obstructions of migration can be created also by section with insufficient flow or with high pollution Interruption of lateral connectivity with flood plain caused by flood protection dikesor by heavy-handed river trainings Fish migration to the side river arms, which usually conserve semi nature character, fish finds hiding place and more suitable flow conditions there Blind river branches (backwaters) represents parapotamon, it means locations of still water, therefore they are sought after above all by limnophylous fish species Migration due to search of stands, for example litophylous fish species searching for gravel bars fitting for their reproduction Migration to the flood plain in phase of flood discharge, especially phythophylous fish species searching for spawning areas at flooded meadows Flowing waters (eupotamon), main rivers and sidearms Permanent or temporarily still water habitats influenced by flow in river (plesiopotamon) or without significant interference of flow in river (paleopotamon), backwaters, oxbow lakes and pools at flood plain Floodplain meadow, their flooding is important for natural spawning of phythophylous species of fishes

Floodplain forests


Examples of rivers in Europe

Ythan, Scotland.

Rhine, The Netherlands.

Meuse, France.

Fuscher Ache, Austria (Photo: J. Peters).

Dyje, Czech Republic.


Narew-Biebzra concluence, Poland (Photo: J. de Leeuw).

Jijia, Romania (Photo: M. Boelens).

Morava, Czech Republic.

Volga floodplain, Russia (Photo: E. Winter).


Sometimes fish swim large distances when looking for food, depending on the food demand of the species, the population size, the availability of food and the schooling behaviour of the species. Migrations between day and night refuges are also common, often involving small distances from open water to the riparian zone.

adult stage. As an adult they migrate for spawning back to fresh water, often homing very specifically to their birthplace. The catadromous eel enter freshwater as juveniles where they grow to maturity prior to their return migration to salt water for spawning. Amphidromous species like flounder, herring and mullet are marine species that can also stay in fresh water, their migration occurring for refuge or feeding.

Other fish movements that could be classified as migration are those undertaken to escape threatening environments such as water pollution, high water temperatures, low oxygen concentrations, high- and low river discharges and drying out of river sections. These circ*mstances affect the survival of fish populations directly and are perhaps more correctly classified as ‘dispersion’. Dispersion is a local population-scale phenomenon rather than a reference to migrations of individual fish. Free interchange between small populations or sub-stocks is necessary to avoid inbreeding. Small isolated populations are vulnerable to local extinction, even when the environment is appropriate. Dispersion makes it possible to enlarge the habitat and to colonise new waters. In this guidance the term ‘fish migration’ is used for seasonal movements, daily movements and dispersion.

Figure 2.2 Migration patterns of salmon and eel in Europe.

Figure 2.2 demonstrates the anadromous life cycle of salmon and catadromous life cycle of eel. Some anadromous or catadromous species contain populations which migrate within a local or regional area, usually because connections between saltwater and freshwater are blocked. These landlocked populations can resume the anadromous or diadromous life history once more if these connections are restored.

Migration patterns Based on migration behaviour, fish can be divided into potamodromous and diadromous groups. Potamodroumous species live in fresh water and migrate over local to regional distances. Migration can be lateral, from river to floodplain, or longitudinal from river mouth to small running waters upstream. Diadromous species migrate during their lifecycle between saltwater- and freshwater habitats. They can be divided into anadromous, catadromous and aphidromous species. Anadromous species like Atlantic salmon, sea lamprey, Atlantic sturgeon and the shads reproduce in fresh water and migrate to the sea where they grow to the

Migration behaviour Seasonal migration of fish is sometimes extensive but can be manifested in an irregular way. The exact migration period can vary each year, as it is stimulated by internal and/or external physiological change and by external factors such as changes in light level, hydrology, water quality or temperature. Dispersion and


2.3 IMPACTS OF BARRIERS ON FISH MIGRATION Barriers to fish migration can have profound consequences for hydrology and habitats, riverine fisheries and upstream and downstream migration of fish. The possible consequences of barriers, such as weirs and sluices, are discussed below as well as other factors that cause migration problems.

displacement, predator avoidance and prey availability also trigger migration. The interaction between internal and external factors determines whether a fish will migrate or not. For most fish species peak migration occurs in the period shortly before spawning. Subsequent dispersion of fish larvae occurs mainly in late spring and early summer. Other dispersal movement depends on external factors and can occur at any time during the year. Downstream migration as part of juvenile dispersion mainly takes place during the night, partly as a predator-avoidance response but also due to the fact that juvenile fish have not yet fully developed their mechanism for orientation (Pavlov, 2002).

2.3.1 Hydrology and habitats Constructions for water management cause hydrological changes and interrupt the stream flow of the river continuum. Most structures, including large barrages, flood-control dams, sluices, flood gates etc., are usually built for water conservation during dry periods, for

Examples of different types of obstacles Dam in the River Llobregat, Catalonia.

Weir in the small river system Oude Vaart, The Netherlands.

Dam in the River Svratka, Czech Republic.

Weir in the Canal Eemskanaal, The Netherlands.

“Not only a big problem for fish migration, but also a big

“This weir is a bottleneck for fish migration between the Wad-

problem in the case of algae blooms” .

den sea and two river systems” .


navigation, hydropower, irrigation, for safety or for water supply. Larger structures such as barrages, flood-control dams, etc. can lead to structural channel changes through their impact upon flows with diversity in flow patterns decreasing from source to sea. Below every construction there is a short zone with relatively high velocities and turbulence that subsequently decreases further downstream. The building of barrages and dams in areas with low summer flows increases the duration of the dry period for downstream habitats. Furthermore, structures can block the flow of nutrients through the river system towards the sea through storage within deposited sediments, depending on local stream hydraulics.

serve as nursery habitat for marine, estuarine or diadromous species, is a clear loss to local biodiversity. 2.3.2 Riverine fisheries Dams have generally resulted in negative impacts on riverine fisheries throughout the world (Jackson & Marmulla, 2001). The loss in fishery yield is sometimes compensated by new fisheries in large reservoirs, however this does not generally maintain biodiversity value. Fish yield in floodplain river ecosystems is directly related to the height and duration of floods and therefore dams that reduce downstream inundation of floodplains have an impact on overall fisheries production. Fisheries depending on migratory fish are often severely impacted because movement of these fish along rivers is readily blocked by dams. In many cases series of dams have been constructed and combined impacts are particularly damaging to migratory fish stocks, even if each is equipped with a fish pass.

Flood-control leads to relatively constant and fixed water levels that might prevent inundation of floodplains during seasonal floods. The remaining free flowing stretches within a dammed section depend strongly on the number of structures and the degree of impoundment. These habitat modifications can profoundly affect the ecology of the system, for example specialist invertebrates adapted to flowing stretches (rheofilic fauna) gradually change into more generalist species. Impoundment to create reservoirs can transform faunal composition into communities of species characteristic to that of a lake.

2.3.3 Consequences for fish migration Barriers for fish migration lead to the fragmentation of rivers, resulting in a decline of habitat quality for fish and the isolation of sub-populations of the fish stock. For species that are not able to fulfil their lifecycle, for instance diadromous species, this can have major consequences for stock survival. Decline of habitat quality can also detrimentally affect non-anadromous populations, causing a bottleneck for dispersion to larger habitats. Fragmentation can result in ecological and behavioural changes, physiological problems, genetic degradation and deterioration of habitat structure of rivers.

The natural mouth of a river and its estuary are important as transition zones. A gradual transition of salt concentration and temperature give fish the opportunity to adapt their physiology prior to migration between river and sea. However flood control sluices can impose a distinct and rapid change between salt and fresh water. This can directly or indirectly cause physiological damage to migrating fish that might be poorly prepared for the transition between environments. In some circ*mstances these structures and their management can lead to the flushing out of freshwater species. Loss of brackish and freshwater tidal areas, which also

2.3.4 Obstacles for fish migrations Different types of obstacles for fish migration exist all over Europe, representing problems for longitudinal and/or lateral migrations through obstruction of fish movement, and some represent a great risk for survival of fish. Barriers in


the longitudinal direction present problems for upstream migrations as well as downstream migrations. Barrages, flood-control dams, tidal barrages and sluices, windmills, pumping- and hydropower stations are all examples of potential barriers to upstream migration. Pumping- and hydropower stations can cause severe damage to downstream migrating fish which may pass through pumps and turbines. For other types of barriers the effects on fish migration is not always clear. This is the case with shipping locks, culverts, trash racks, etc.

Other factors that can adversely influence fish migration are water abstractions such as those for cooling water, commercial fisheries, water level management for navigation, flood defence and a range of other uses and the presence of predatory species. In most countries in Europe the most common problems relate to the upstream migration of fish at low head weirs (0,5 m-4,0 m). Weirs are constructed in a variety of ways, but most have a fixed crest and water control structures such as sluices. Most were originally built for the purposes of milling and may have been re-built or modified many times in the past. Today some are used for abstraction (mainly potable and industrial use but also for irrigation), navigation and hydropower but many have been developed and retained for historical and aesthetic purposes. Most countries have many thousands of such structures on their watercourses.

For a better understanding of the problems of barriers for longitudinal migrations, we need improved detailed knowledge of fish behaviour at barriers. The number of barriers in European rivers is of concern and the quality of design and construction of fish pass facilities does not necessarily mitigate the impact adequately. This matter will be discussed next and in the following chapter(s).

Downstream migration In all weir or dam-regulated rivers that contain water intake facilities, damage to downstream migratory fish and impact on fish stocks can be expected. The nature and degree of damage can vary strongly, dependent on the type of water intake and the presence of screens. Large scale mortality of downstream migrating fish can have severe ecological consequences for the fish stock as these losses usually operate after density-dependent factors have concluded. For species such as salmon, compensation through re-stocking is feasible although perhaps not always desirable, however for some others such as eel it is not generally possible to compensate the damage by restocking. If species are important for commercial fisheries a high mortality also has economic consequences due to the loss of fishing opportunity and the reduced harvest e.g. eel, salmon, shad or sturgeon species.

Upstream migration The mechanism of impact of barriers on fish includes: • Large difference in water level and very strong flow; • Too small entrances to fish passes; • Inadequate and weak attraction flow; • Low water levels at and above the obstructions. The mechanisms of impact of barriers on fish migration depend on the swimming ability and behaviour of migrating fish. These characteristics are often specific to the species, life stage, condition and size of the fish and to flow and water temperature. A main obstacle for lateral fish migration is that of dykes and flood banks. These can isolate rivers from potential wetlands in the valley as inundation of the floodplains may no longer occur. Other potential barriers are structures built to reduce or prevent erosion of banks, which can often lead to isolation of the river from riparian vegetation.

In European rivers downstream migrating fish can encounter serious damage as a consequence of:


Title Author Organisation Country

Obstacles in the Upper River Rhine section E. Staub FOEN, Fisheries and Aquatic Fauna Section, Berne Switzerland

Introduction In the Upper River Rhine, there are 11 hydropower plants located within a river length of 150 km, (see figure below). The fish passes at these power plants are periodically monitored to assess the number of fish migrating upstream. In 1985, 1995 and 2005 there were synchronous monitoring studies at all fish passes along the Upper River Rhine.

upstream was found in 1995, however, these data were strongly influenced by an extraordinary high movement of more than 46’000 barbel (Barbus barbus) at the KW Schaffhausen power plant. The number of species registered was highest in 2005 when it reached 32 species, the most dominant of which in all three studies were barbel and roach (Rutilus rutilus). Some species were re-presented by only a few specimens (e.g. 13 species with less than 10 specimens in 2005). The increased number of species is partly the result of improved training and skill of the fishery personnel engaged in the three studies.

Research results Within the past 20 years the number of fish migrating upstream has reduced steadily in most fish passes. The highest number of fish migrating

Map: Hydro-power plants (KW) and its fish passes (indicated with stars) located at the Upper River Rhine between Lake Constance and Basel (LIMNOFISCH, by Bundesambt für Wasserwirtschaft).


Hydro-electric power plants At hydro-electric power plants some damage is almost inevitable, even when protection through screening combined with guidance systems is in use. Damage by passage through turbines varies from 5 to 40%, but can be higher and up to almost 100%.

Pumping stations Pumping stations are often used in the lowlands of the Netherlands, Germany and Flanders for the purpose of water management to maintain water levels and reduce the risk of flooding. Damage to fish during passage through pumping stations is comparable with hydro-electric power plants.

pass over a spillway and fall into the pool downstream. Significant damage, including injuries to gills, eyes and internal organs, can occur when the impact velocity exceeds 15-16 m/s. This critical velocity is reached after a free fall of around 30-40 m for fish of 15-16 cm and 13 m for fish longer than 60 cm (Larinier et al., 2002). Tips 1. General and local knowledge on the fish species present and their migrations and the biological hydrological and hydraulic nature of the river system, are the basis on which problems for fish migration and the design of solutions should be tackled. 2. Rivers need to be considered as a network of surface waters, groundwater and coastal waters within a river basin that together function as a total ecosystem. Restoration of fish migration is only part of the solution when working on ecological restoration of river systems.

Industrial and potable water intake In many river systems water is used for industrial purpose, including cooling and potable supply. In some cases these abstractions may not require impoundment through a weir or dam, however in all cases fish entrainment is a risk. In the vicinity of a water intake, flow velocities increase and these can be interpreted as a guiding or attraction flow by downstream migrating fish. Fish are orientated to the principle flow line in order to continue their migration and can therefore be led into an intake where they are exposed to the risk of injury and mortality.

Mechanical barriers Racks or screens are used to prevent trash or debris entering into water intake facilities used for industrial water supply, for turbines and pumping stations. Most damage occurs due to impingement of fish as a consequence of high and sustained flow velocities towards the rack or screen. According to Beamish (1978) most fish can overcome flow velocities of 0,5 m/s if they are motivated to do so.

Large drops over the weir or spill way Injury or mortality can occur when fish

2.4 IMPACT OF COMMERCIAL FISHERIES Actively migrating fish are also affected by interceptory fisheries that exploit the often high economic value of the fish. Those operating the fisheries have learned where and when fish migrate and have developed their methods to maximise their effectiveness. Consequently the fisheries interrupt migration through removal of large quantities of fish. This has been very significant in some cases, for example the glass eel fisheries within the estuaries of Spain, Portugal, France and the UK and the estuarine fisheries for sturgeon have severely depleted the stocks. Similar local levels of exploitation for many other species, notably salmon has also had serious local implications for stock viability.


Title Author Organisation

European Eel, Current status in Europe Estibaliz Díaz Silvestre AZTI - Tecnalia / Unidad de Investigación Marina, Basque Country, Spain

Introduction The European eel (Anguilla anguilla) is found and exploited in fresh, brackish and coastal waters in almost all of Europe and along the Mediterranean coast of Africa and Asia (Moriarty and Dekker, 1997). The life cycle is not completely understood, but current evidence supports the view that recruiting eel to continental waters originate from a single spawning stock in the Atlantic Ocean. The population of the European eel is in rapid decline, recruitment of juveniles to the continent having dropped since 1980 by nearly an order of magnitude per generation (Dekker 2000a). The relative significance of a range of factors causing the decline is not clear, however it is accepted that the following ones have a negative effect on eel population: • Fisheries The estimated annual catch of eels (all stages) is of 30,000 tonnes according to Moriarty and Dekker (1997). This fishery employs a large number of people in the EU; in fact, current estimates put the number of European eel fishermen at about 25.000. • Barriers to upstream migration Dams in rivers impede the upriver migration of glass eel and elvers. Although it is accepted that barriers cause an overall loss of silver eel production, since natural mortality is higher in downstream areas (Briand et al., 2003), the net effect of all barriers on the total population is unknown. • Entrainment during downstream migration Silver eel passage through hydropower turbines poses risks of immediate death, serious injuries, or damage with delayed


effects (Dekker, 2004). Up to 100% of the eel entering the headrace of a turbine may be injured (average 30-70% Larinier and Dartiguelgongue, 1989; Larinier & Travade, 1999), but effects of hydropower stations on overall stock remains unknown. Habitat loss Land reclamation, swamp drainage and various water developments have reduced the eel habitat. Predation The principal eel predators are cormorants which have increased by 60 times the number of breeding pairs since 1970 (Van Eerden and Gregersen 1995). It has been demonstrated that eel has a considerable presence in their diet (ICES 2003). Environmental factorsClimate change and ocean currents There is some evidence that climate change is affecting eel recruitment; the decline in recruitment of A. rostrata and A. Anguilla coincided with the North Atlantic Oscillation (NAO) in the 1980. Loss of spawner quality The eels migrating from European rivers are adversely affected by the following factors that limit their capacity to reach the Sargasso Sea spawning area and/or produce viable offspring (EELREP, 2005): • Contaminants PCB’s accumulate in the fat stores of eel and reduce energy consumption of both swimming and resting eel and have deleterious effects on the fertility. • Virus infection Evex infection is become widespread on European eel population and infected silver eel will never reach the spawning grounds.

Swim bladder parasite The infections with Anguillicola crassus reduce swimming capacity and heavy infection will prevent the migration to the Sargasso Sea.

stock must be compiled and implemented as a matter of utmost urgency and based on a precautionary approach, urgent protective measures should be taken: anthropogenic impacts must be curtailed, where they exceed sustainable limits. Following the scientific advice from ICES, in October 2005 the EC proposed a “Council Regulation establishing measures for the recovery of the stock of European eel”. The objective of the proposal is “to achieve a recovery of the stock of European eel to previous historic levels of adult abundance and the recruitment of glass eel” and to ensure the sustainable use (fishing) of the stock.

Research and management The dramatic decline of the eel population in the 1980s and the subsequent urgent need for management plans stress the lack of information regarding the population. For any measures to be effective managers need an information base of properly coordinated recruitment surveys, reliable landings statistics and assessments of the impact of exploitation and habitat loss.

The principal element of the proposed Regulation is the establishment of eel management plans for each river basin, including transboundary basins (as defined according to the Water Framework Directive). The objective of each river basin management plan shall be to permit, “with high probability”, the escapement to sea of at least 40% of the biomass of adult silver eel relative to the best estimate of the potential escapement in the absence of human activities affecting the fishing area or the stock.

For that reason, the Eel Working Group, (WGEEL: www.ices.dk/iceswork) jointly organized by the European Inland Fisheries Advisory Commission of the FAO and ICES, started to collect the available data, began to fill the data gaps and initiated the development of new management concepts for a scattered, but shared stock. Since 1999 the group has recommended that a recovery plan for the eel

European co-operation The INDICANG INTERREG project also deals with eel research and management (www. ifremer.fr/indicang). The starting date for the project was May 2004 and its duration is 3 years. The project is supported by 7 regions of the Atlantic Arc: Northern Portugal, The Province of Asturias, The Spanish part of the Basque Country, Aquitaine, Poitou-Charentes, the Loire region and Cornwall in England. The aim of the project is to set up networks to measure the abundance and the colonization of the European eel at a scale covering the central part of its distribution area. The main product

Photo: Hydro-power turbines pose a serious risk for eel migration.


Data collection The eel has been included in the EU Data Collection Regulation (Council regulation 1543/2000 and Commission regulations 1639/2001, 1581/2004). Required sampling levels have only been indicated tentatively and only a few countries have actually included eel in their sampling programmes. A workshop on data collection for the European Eel from 6th-8th September 2005 specified minimum requirements on sampling levels for fishery-dependent and fishery-independent data, for the three exploited life stages (glass eel, yellow eel and silver eel), in both inland and coastal waters.

of the project will be an internet network with eel dedicated websites that summarise the situation on every pilot catchment. The common plan for these websites will be: Exploitation Resource - Environment. To ensure that abundance figures, fishing statistics and characteristics of habitats can be compared from one catchment to another, the data must be collected according to standardised methodologies. These methodologies must be validated within a network of “thematic working groups”. The 4 thematic working groups are: “the glass eel index group’’, ‘’the yellow eel group’’, ‘’the silver eel group’’ and ‘’the habitats group’’.

Photo: Fishery in the Ebro Delta.


3. Policy, legislation and financing Effective legislation and policy are essential in order to protect species and their natural habitats. In some countries legislation for the protection of riverine fisheries has been in place for many years. For example in Germany the building of fish passes was incorporated in a former version of the Prussian Fishery Law of 1874 whilst in the UK legislation requiring the removal of obstructions to migrating fish was enacted as early as the 15th century. Such regulations addressed many local problems however the number of obstacles that remain in these countries and throughout Europe demonstrate the need for refined legislation and policy. A comprehensive river basin approach for fish migration demands collective policy on an international and national level.


3.1 POLICY AND LEGISLATION 3.1.1 Europe Modern regulation of environmental threats and problems is increasingly effective within the EU. New and emerging international law seeks to deliver good ecological status and this includes restoration of populations of migrating fish such as salmon, eel and trout. In many cases direct funding of facilities to achieve this is made possible through EU subsidies. EU directives are transposed into national legislation and may support existing national legislation that serves national interest concerning management of flora and fauna and the economical interests of the country. Law and policy on a local level are increasingly focused on the implementation of international and national laws by national regulation. This may increasingly lead to targeting of national funds to address local need for environmental management including that of migrating fish. This chapter summarises international, national and local legislation and policy with respect to fish and the restoration of fish migration in Europe.

On a European level there is substantial legislation that is directly relevant to the restoration of fish migration in our river systems. The most important is discussed below. More information can be obtained from the EU website (www. europa.eu.int).

The WFD is the most substantial legislation relevant to ecological condition and to the well-being of migratory fish, however it is not the only legislation.

The aquatic environment is improved, e.g. through substantial reduction in discharges and emissions; The sustainable use of water is promoted on the basis of long-term protection of available water resources; Groundwater pollution is reduced considerably.

WFD demands that we ecologically optimise the use of rivers at acceptable cost and this will extend to targets for fish stock and migration. Ecological monitoring programs must have been developed and implemented in 2006 and in 2009 the River Basin Management Plans and associated Programmes of Measures for each of the river basins will be implemented. The identified targets for each basin should be attained by 22 December 2015 when the results of ecological monitoring will be compared with the relevant targets. For more specific information on the objectives established by the WFD for surface water see http://europa.eu.int/comm/ environment/water/index.html.

Treaty of Bonn (concerning the protection of migrating wild animal species, appendixes I and II, dated 23 June 1979). Section 2 of this treaty recognises the importance of migrating fish species and requires appropriate measures to be taken to insure the preservation of migrating species.

Water Framework Directive (Directive 2000/60/EC). The Water Framework Directive (WFD) provides a framework for the protection of inland surface waters, transitional waters, coastal waters and groundwater. The Water Framework Directive is valid for all Member states of the European Union, although the Member states have a certain freedom to determine how the WFD is integrated in their own national legislation. The Water Framework Directive intends to ensure that: • Aquatic ecosystems and areas directly dependent on these ecosystems are preserved from further deterioration;

Treaty of Bern (concerning the preservation of wild animaland plant species and their natural habitat, appendixes I, II, III, IV, dated 19 September 1979). This treaty aims for the preservation of wild plant and animal species and the habitats they depend on. The treaty is also designed for situations where co-operation is needed


Title Author Organisation Country

Conservation of eel in the Netherlands A.J. Scheper Fishery Board of Groningen-Drenthe, Tynaarlo The Netherlands

One of the most widely distributed and abundant fish species in Europe is the eel (Anguilla anguilla). The eel is an ecologically and economically important fish species in the Netherlands. In recent decades, the eel population has declined by nearly an order of magnitude per generation. Research to identify the reasons for this decline suggest that natural processes may be responsible for the decline. Confirmation of this is not currently possible as we still have insufficient understanding of the ecology and the lifecycle of the eel and historical population data is inadequate to confirm the factors causing the decline. Recent research (Dekker, 2004) indicates that mortality during the adult (continental) phase of the eel increased over the second half of the 20th century and this is likely to have reduced the number of spawning eel. This presumably has lead to significantly reduced reproductive success. Knights and White (1998) quote figures indicating that about 7% (200,000 ha) of the still water habitat and 25%

(68,000 ha) of the riverine habitat in Europe are inaccessible to eel due to man-made barriers. The combined impact of commercial fisheries, pollution and obstructions to migration have lead to production of an “eel plan” by the Dutch ministry of LNV (Agriculture, Nature and Food quality). The plan seeks a combined European plan with targets on: • Specific national measures; • Information exchange; • Co-operation between interested parties; • Optimizing future research of eel. Measures In the Netherlands measures are focused on enlargement of accessible natural habitats, optimizing migration of glass eel and adults and a larger quantitative and qualitative monitoring programme. The results should be: • More eel reach the adult stage; • More adults reach the Atlantic Ocean; • More glass eel enter the inland waters.

Photo: In the past large areas in the Netherlands were restocked with elvers. Nowadays the focus is more on restoring natural migration.


Title Author Organisation Country

Legislation for downstream fish migration in England & Wales G. Armstrong Environment Agency, Bristol United Kingdom

This situation was of great concern because migratory salmonids have returned to the river after an absence of 110 years between 1860 and the 1970’s. The absence was caused not only by the weir and diversion of the water course for the docks, but primarily by pollution from the great nineteenth century industries in this Welsh valley.

Current statutory legislation in England & Wales offers protection for downstream migrating salmonids - salmon and sea trout. Section 14 of the Salmon & Freshwater Fisheries Act, 1975 (SAFFA) ensures that in waters frequented by migratory salmonids any conduit or channel abstracting water for potable supply, channels, mills (which includes hydopower applications) or fish-farming must be screened to prevent the ingress of fish. In the case of fish-farms the outlets must also be screened to prevent egress of fish. Where screens are provided in a channel they must have a continuous by-wash. The provisions are not applicable to conduits or channels constructed before 18th July 1923 and do not apply to other species of fish. Section 15 of SAFFA provides power for the Environment Agency to place and maintain screens at its own expense. Fisheries legislation in England & Wales is currently being reviewed. It is anticipated that when new legislation is passed it will include provisions for all species of fish, rather then just migratory salmonids.

Photo: Screen on the River Afan in South Wales.

In 2004 the Environment Agency used its powers under S.15 of SAFFA to install a set of screens across the channel that feeds water to the docks for navigation and other purposes. This was done in the modern spirit of collaboration with the major industrial users, including the docks themselves and the steelworks that abstract water. The project was jointly funded and also included a financial contribution from European Union Objective 1 funding. Salmon and sea trout, smolts and kelts are now safely diverted away from the docks and abstractions, where they would otherwise be lost and over the weir into the channel that runs directly to the sea.

An example where the legislation has been used to protect downstream migrating salmonids is on the River Afan in South West Wales. In 1836 an Act of Parliament enabled a Port & Harbour to be built on the line of the natural river estuary and using the river flow, with excess flows only diverted over a weir and new channel to the sea. This is outside of the jurisdiction of the Act and all river flow can legitimately be diverted to the docks for navigation and can also be abstracted for other industrial purposes without the need for screening by the user.


between different countries (Lelek, 1980; Lelek; 1996).

formulated targets regarding fish migration in their water bodies. In the federal states of Germany, e.g. Lower Saxony or Nord Rhein Westfalen, fish migration is also incorporated in legislation. The Flemish region of Belgium uses a map of priority waters where all problems with regard to fish migration should be solved by January 2010. In England and Wales, obstructions to migration of salmon are targeted for action within Salmon Action Plans, delivery of which is subject to a Government Ministerial Direction.

Regulation 92/43/EEG of the council of European communities (concerning the preservation of natural habitats of wild flora and fauna dated 21 May 1992). This directive aims to establish a ‘favorable conservation status’ for habitat types and species that have been selected as being of EU interest. An European ecological network known as ‘Natura 2000’ will be established. For more information see: www.europa.eu.int/ comm/environment.

Tips: 1. Use the river basin plans, that must be prepared by 2009 as part of the WFD, to seek restoration of fish migration in rivers systems. 2. If it does not already exist, consider promotion of legislation on a national or regional level, whereby all new (or under restoration) weirs, dams, sluices, hydropower or pumping stations etc. provide a facility for up- and downstream migration of target species. 3. Promote the use of fish friendly water intakes, e.g. cooling water, pumping stations and hydropower, that exclude fish through screening or by restricting intake water velocities to those that target species can avoid. 4. Produce an action plan to deliver the fish migration facilities that are required. A map of the region with priority waters can be very useful. 5. Fully implement European policy in your national or regional policy concerning restoration of fish migration.

Treaty of the Committee of ministers of the Benelux Economical Union (concerning the free migration of fish species in the hydrographical basins of the Beneluxcountries, dated 26 April 1996 M (96) 5). Section 2 of this treaty requires the governments of the Benelux countries to ensure the free migration of fish species in all river basins. Priority goes to the migration of the larger anadromous and catadromous fish species from and to the spawning and nursery areas. This must be achieved by 1 January 2010. 3.1.2 National and regional Other than EU directives and treaties, legislation and policy varies considerably between each country. It is clearly important that those working on fish migration issues are familiar with the legislation on fish migration and the available mechanisms to solve fish migration problems. This is the basis for action on fish migration issues. Regional policy should be based on international and national policy adjusted to suit further specific (local) information. Some regional or local requirements, such as planning conditions, may not be enacted as legislation whilst others, for example those made by federal states, municipalities or water boards, might. Some Water Boards in the Netherlands have


Title Author Organisation Country

Intertidal transition zone Breebaart polder-Waddensea H. Wanningen Hunze en Aa’s Waterboard, Veendam The Netherlands

The nature conservation area Breebaart is situated in the North of the Province of Groningen on the Dutch coast line. A former agricultural area has been restored as an intertidal area by construction of a culvert through which the sea can freely enter the polder. This has restored the natural transition between fresh water and seawater. A combined fish friendly jackscrew and a device to provide a clear migration route makes the area accessible for diadromous fish species like the three-spined stickleback, smelt

and eel. The maintenance of the fish pass, which was built in 2001, is partly undertaken by the Hunze and Aa’s Water Board and the Foundation Landscape Groningen. The range of interests in the project resulted in the project and the fish pass financed coming from diverse range of sources. These included nature development interests, water management and an existing international partnership. The Hunze and Aa’s Water Board financed 10% of the total budget.

Photo: Impression of the Breebaart Polder on the right and fish pass in the centre.


• • • • •

EDR; INTERREG IIIA program Dutch Oil Company (NAM) Hunze and Aa’s Water board North Netherlands Directorate for Public Works and Water Management Government Service for Land and Water Management (DLG)


Percentage of investment in fish passage

Percentage expressed in euros

40 30 10

127.200 95.400 31.800







Table: Contributions of investors in the fish pass at the Breebaart polder expressed in percentages and euros.


There are several European programs which can support European partnerships to address the problems of fish migration. These include: • Interreg programs: this is a program focusing on issues concerning spatial planning of which sustainable water management and ecological improvement is one of the priorities. Within the program there are several possibilities (e.g. www.interregnorthsea.org); • Interreg IIIA, IIIB and IIIC; international programs for co-operation in Europe. (e.g. www.interreg-medocc.org; www.interreg3c.net; www.cadses.net); • LIFE Nature: program to improve the quality of existing natural areas. Improvement of the biotope of fish species in natural areas can be subject of a project which can take place in a single European country (e.g. www.europa.eu); • LEADER plus: program to improve the quality of rural areas in European regions; • POP: program to support the sustainable development of the European countryside.

Photo: Fish pass Kubach, Germany (Floecksmühle Ingenieurbüro).

3.2 FUNDS FOR FISH 3.2.1 Europe Fish migration is a matter that fits well within prospective European co-operation. Problems with fish migration, as well as other ecological river problems, are not constrained by borders and need to be looked upon in a wider context. This is especially the case for the largest river catchment areas, where there is a need to consider fish migration problems in a multicountry context and where actions to solve the problems probably need to be taken in each country. Fish migration problems need to be placed in the context of other problems concerning, for example, water quality, water safety management, recreation, fisheries and biodiversity. The solution often needs to address a range of problems of which fish migration may be just one. The European Water Framework Directive requires nations to look upon the ecological problems of rivers within an European and an integrated perspective.

Tips when seeking and working with subsidies: 1. Understand the range of international, national and corporate grant schemes that offer funds. 2. Plan your work on fund raising, developing your knowledge-base and developing contacts with your own colleagues, with specialist consultants and with administrators of funding sources. 3. Take the administrative obligations seriously and organize this well. 4. Link the objectives of your fish migration project to European water management and biodiversity policies. 5. Use regional/provincial contacts in Brussels for the promotion of larger, multi-country projects.

There are two strategic approaches for water and fishery authorities to work on a European level regarding fish migration: 1. Develop strategic, regional partnerships concerning river improvement and fish migration; 2. Develop strategic knowledge-based partnerships concerning fish migration.


Title Author Organisation Country

Fish migration solutions in West Brabant R. van Nispen Brabantse Delta Water Board, Breda The Netherlands

Introduction Fish passes have been built south of Breda by the Brabantse Delta Water Board, funded by the INTERREG IIIA project IASM. The water quality and water quantity problems in the Aa of Weerijs and Bovenmark, both of which rise in Belgium and are situated south of the city Breda, were the reasons for initiating an Interreg IIIa project between Belgium and the Netherlands. The main targets of the project were to improve water quality, aquatic ecology and water quantity of watercourses crossing the border. The main measures used to improve aquatic ecology were construction of fish pass facilities to establish upstream migration and to restore channel morphology. Target fish species for both brooks are ide, dace and bleak. In the Aa of Weerijs the main fish pass facilities are vertical slot –passes, whilst in the Bovenmark pool passes in combination with parallel streams were used after crossing the Dutch border. Both brooks join the channels of Breda and they form important fish ecological connections with the Mark-Vliet system, Lake Volkerak/Zoommeer, The Easten Scheldt and the North Sea.

and research of fish pass facilities. During 2005 and 2006 several vertical-slot and pool passes in the Netherlands and Belgium were evaluated. The Brabantse Delta Water Board used an automatic fish counter in the small river Bovenmark for fish pass evaluation. This method is frequently used in England for monitoring salmon.

Photo: Fish pass in small river Bovenmark.

The Aa of Weerijs and Bovenmark form important ecological connections between the Mark-Vliet system and downstream brooks south of Breda. Within the Interreg IIIa project IASM both Belgium and the Netherlands have established their own projects, but to ensure targets were achieved a Dutch-Belgium committee was installed. During the project the finance administration of the Interreg projects was supervised by the Brabantse Delta Water Board. Fish pass evaluation An important part of the project is the evaluation


3.2.2 National Most countries have various arrangements requiring the incorporation of fish passes at new structures, but most do not appear to have a specific financing programme for fish passes at old weirs. This is a problem for the large legacy of frequently redundant industrial weirs. However this is not always the case. In some countries, including Sweden, Belgium, Czech Republic and Finland, state funds are provided for programmes to restore fish migration in river basins.

utility and private organisations are also quite common. For example in Luxembourg this occurs in relation to hydro-electric power stations, whilst in the Netherlands this is part of gas exploitation1. In Italy many fish passes have been financed and built by the owner of dams in order to fulfil compulsory prescription defined by the competent authorities during the EIA or authorisation phase. Funding of fish passage facilities is therefore through a variety of means, including government subsidies, income from fishing licences, through private funds and can in some circ*mstances be supplemented by European funds. In practice most fish passes are funded by collaborative means making use of a multitude of different funding streams.

In Lithuania funding for fish migration is part of a state investment programme. In other countries such as the Czech Republic fish passes on newly built river structures can be ordered by law and therefore their financing is provided by the developer as part of the national Programme of Revitalisation of River Systems. In the UK the inclusion of a fish pass of approved design can be ordered as part of any new weir development or where an existing weir is the subject of substantial repair or renovation.

Specific facilities for downstream migration appear to be less common. Many that exist are at hydropower stations where they are built by the licence holder under requirements identified as an obligation for the licensees Tips: Some issues with funding fish passages facilities: 1. Look for or initiate partnerships to source budgets for fish migration projects. 2. Combine fish migration projects with strategic ecological restoration projects. 3. Use ’the polluter pays’ principle.

The construction of fish passes at state-owned weirs, for example in important navigable waterways is usually funded from income derived from navigation licenses and sometimes also from government grants. Compensatory and mitigatory funds from the state or from public

Photo: Dam in the river Dronne, France.


Gas exploitation leads to settling of the bottom and consequently to rising of the water level. Additional pumping stations and weirs are necessary in order to maintain water levels and public safety.



4. River basin approach Most rivers in Europe have the status of ‘heavily modified’ (Water Framework Directive) and for these it is very questionable whether good ecological status is achievable before 2015. Sometimes it is not possible to establish fish migration facilities simply due to financial or in some cases technical limitations. Targets for restoration of fish migration should be considered very carefully, taking into account available habitat and upstream and downstream migration within the river continuum.


4.1 INTRODUCTION Fish migration problems should be approached on a whole river basin basis as part of a holistic management plan, as proposed in the Water Framework Directive 2000. This approach will establish the species that are characteristic for the type of water body and their requirements for migration within the river system together

with other constraints to improvement. However how can rivers be prioritised for restoration of fish migration and is it necessary to achieve full connectivity from sea to source in order to maintain or restore these species? Pragmatically it is often necessary to focus ambitions on priority waters and to set targets for certain species or a group of species.

The basic steps, using the River Basin Approach, consist of: Step 1.

Objectives for fish migration in a whole river basin

Upstream: • Identify target species; • Quantify amount of species upstream migration. Downstream: • Identify target species; • Quantify the required survival rate of species migrating into marine waters. Other ecological targets: • Quantify the minimum and maximum amount of flow; • Quantify amount of suitable habitat of the river stretches that are connected.

Step 2.

Prioritise waters within the river basin

Biologists, engineers, specialists on hydrology/water management and town- and country planners to agree priority waters based on: • Ecological need and technical potential; • Opportunities to link with other projects; • GIS-map and data base.

Step 3.

Priorities of measures

Obstacles for upstream migration: • Agree the criteria for planning (financial, ecological or other); • Prioritize measures (high, medium or low) Indication of efforts and costs. Obstacles for downstream migration: • Indication of efforts and costs.


4.2 AMBITIONS For each river within the river basin district, objectives for fish migration should be formulated. An objective might, for example, be to realise free migration (up- and downstream) of target species from sea to source or, alternatively for some rivers simply to ensure no further degradation of fish migration potential (a “no detriment” principle). A whole basin plan should seek to protect and enhance the migration potential for all of the fish species present. The objectives should complement and support the total ecological objectives for the river basin and they should therefore preferably be integrated with local or regional plans of appropriate partner organisations.

The restoration of upstream fish migration within the river basin will present a substantial challenge for many rivers within the first river basin plan, delivery of which is required by 2015. The plans will describe a future objective for the state of the water bodies in order that they may support healthy and sustainable stocks of the prescribed target species. Criteria for selection of target species are: • That they have an original distribution in the river basin; • That there is a realistic chance for restoration of a sustainable population; • That they have a high demand for habitat quality and connectivity of habitats; • That they are part of national or EU policy; • That they are of relevance for different stakeholders. It is important that objectives are quantified, for example by defining the abundance of a species in a river system that is necessary for a sustainable population. Quantification is also relevant for habitat features such as the occurrence of freely flowing stretches that are not modified by weirs. Tip: 1. Set your ambitions, objectives and goals “from sea to source”. In this way you show that you think and work on the scale of river basins and that the problems are tackled in the most effective way.

Photo: Cal Rosal weir, a typical fish migration barrier in the Llobregat River, Catalonia.

It is likely that the target species, those which are characteristic for the type of water respective to the Water Framework Directive, will already be well known. Targets for fish migration will be an intrinsic part of overall targets for fisheries and for natural and ecological targets and should hopefully gain broad social acceptance. Objectives must at least achieve “no detriment” for fish passage and this should ensure no further decline in the species due to habitat fragmentation and blockage of migration routes. Clearly it should be the objective to achieve much more through the restoration of fish migration routes as appropriate.

4.3 PRIORITY APPROACH Once strategic objectives are established it is important to prioritise waters within the river basin for action. Most modified rivers in Europe contain many weirs, small dams, hydro-electric power stations and a range of other migratory obstructions that have been built over the past few centuries. In some of the largest river systems the total number of obstacles can exceed a thousand, several of which may be complete


Title Author Organisation Country

From sea to source. Targets for fish migration in river basins in the North of the Netherlands. P.P. Schollema1 & J. Huisman 2 1 Hunze en Aa’s Water Board, Veendam 2 Noorderzijlvest Water Board, Groningen The Netherlands

vantage of such a map is that the bottlenecks are clearly visible and it is clear to see which bottlenecks have priority. The vision seeks to remove the migration bottlenecks for fish situated within these watercourses within 10 years. The objectives must be reached by 2015. This systematic approach identifies the relevant bottlenecks, prioritizes, identifies and measures to resolve the problems. It also seeks to identify the opportunity to deliver solutions in partnership with others to maximize the value of possible subsidies. Furthermore, the vision stresses the importance of using natural solutions to improve fish migration first and, when not possible, the technical fish pass solutions that are required.

One of the most important policies concerning fish migration created by the Water Boards Hunze en Aa’s and Noorderzijlvest is the vision “Van Wad tot Aa” Groningen Northern-Drenthe 2005-2015. This shared vision is created together with the Groningen-Drenthe Fishery Board (Riemersma & Kroes, 2005) by a team of representatives working in partnership. One of the important principles for the partners was that a structured approach was needed to prevent further decline of the potential for fish migration. The vision differentiates between coastal constructions, obstructions within rivers and brooks and structures preventing lateral migrations to floodplains. This was done because each type of landscape needs a different approach and the vision sets objectives for representative fish species in each of these different areas.

An important instrument which is used to make regional policy is the so-called ecological connection zones. These are zones that connect ecologically important areas with each other and seek to ensure that fauna as well as flora can freely interchange between these areas. Rivers and brooks are often used as ecological connection zones, Because they effectively link geographically distinct areas. Key target species are used to measure the quality of these zones, one of these being the river lamprey .

The vision has two themes: 1. Prevention of further deterioration of fish migration potential (the “stand-still” or “no detriment” principle) whilst seeking as many opportunities as possible for improvement through, for example, major repairs to structures or by proposing new standards for fish passage within new developments and renovations. This approach is applicable to all surface water bodies within the management area and to all artificial constructions and is supported with a number of decision models; 2. Solutions for migration bottlenecks identified in the vision. The vision prioritizes the bottlenecks by creating a so-called fish migration map that identifies all bottlenecks in the management area. The ad-

Fish species within the local brooks are protected by the “Species protection plan for brooks in the province of Drenthe”. This policy describes the typical fish species found in brooks and what should be done to protect them. It is a typical example of regional policy, because it is only valid for the river basins in the province of Drenthe.


Map: Fish migration map of Water Board Hunze en Aa’s; priority waters, bottlenecks and solutions.


obstructions to fish passage but many of which might only be partial barriers. It is not necessarily the case that all obstacles should be made passable for fish to achieve the relevant objectives and it might not be affordable. It will generally be important to prioritise rivers within a river basin for the purpose of fish migration.

fish can be sustained in these waters. Even if fish passage and survival at some sites is as high as 95%, the cumulative impact of a succession of similar sites can be very damaging. It is again important to prioritise rivers and river reaches for action where improved protection will deliver the objectives. Examples of priority rivers and waters are: • Those that are part of national or regional policy or agreed action plans, for instance in Germany (region Nordrhein-Westfalen) waters that are mentioned in a migratory fish program are prioritised; • Where important stocks of anadromous and catadromous fish exist or where there is potential to restore them.

One possible approach might be to select ‘natural waters’ as priority waters, followed by the ‘heavily modified waters’ and then the ’artificial water bodies’. Each might be important for sustainable existence of some target species. Alternatively selection of waters can be on the basis of known distribution of target species and by expert judgement.

Tips: 1. Solving fish migration problems is most effectively addressed by a multidisciplinary team of hydrologist, ecologist and engineers. 2. The best solution for fish migration problems may not be a formal fish pass, but a natural solution such as restoration of old meanders or the creation of a nature-like bypass channel.

For diadromous and potamodromous species migratory routes can be identified on the obvious basis of drainage direction of the rivers in the river basin. In opening migration routes it is important to secure passage progressively, working upstream for anadromous species, but it is also important to maximise other opportunities as they arise. Prioritisation should be undertaken by a multi-disciplinary team consisting of biologists, engineers, hydrologists and water managers, supplemented by planning specialists. It is important to recognise an opportunity to enter partnerships with other projects (e.g. land use/planning, water management, ecological restoration etc.) that might give rise to more cost-effective solutions. The outcome of prioritisation should preferably be a GIS (Geographic Information System) based action plan that clearly sets out the priority waters and the migratory obstructions that they contain.

4.4 PRIORITIES OF MEASURES Once priority waters have been confirmed potential solutions to the obstructions to migration can be identified. Full restoration of fish migration routes in river systems may be a very difficult and expensive goal, especially when a chain of many obstacles needs to be addressed. In most cases it is simply not possible to resolve all of these at once and for this reason a phased approach is often required. Prioritisation for action should be on the basis of criteria agreed at the outset and the timescales for action should be in line with those of the Water Framework Directive. It may be the case that more than one solution might be identified to resolve an obstruction and, subject

The approach should be similar for downstream migration with a comprehensive plan to resolve all potential damage causing barriers and/or intakes in a river system. The cumulative impact of barriers must be considered in producing an action plan. In some rivers the cumulative damage can be too large and it may be questionable whether populations of some


Tips: 1. Set objectives for the river basin based on the target species, priority waters and priory measures and then estimate the resource requirements to deliver it. 2. The target species for upstream migration should consist of the characteristic riverine species, as described for the WFD. Target species for downstream migration should be identified on the basis of risk and will probably include at least the diadromous species and often several potamodromous species. 3. Targets for the river basin should be quantified, e.g. total % survival and passage to the estuary for downstream migrants and the total % of a migratory stock species (or present densities) required at a prescribed upstream location. 4. Fish migration problems need to be placed in the context of other problems concerning, for example, water quality, water safety management, recreation, fisheries and biodiversity. The solution often needs to address a range of problems of which fish migration may be just one.

to an assessment of the costs and benefits of each it is preferable to select the most natural solution (see paragraph 5.3.1). The final prioritisation plan must provide an indication of resources and finance that will be required within each phase of action. The protection of downstream migrants can be more difficult than upstream and in order to further develop techniques and to gain the support of appropriate industry, it would be helpful to develop pilots where damage is known to occur. A full evaluation of the technical solution and the benefit for the fish species concerned would be required. In most significant surface water abstractions, it is likely that construction of appropriate mechanical barriers would be required. Depending on the site these might be very large and expensive. In the UK passive wedge-wire screening is regarded as the best available technology, but is not always appropriate to use technically, or when taking in to account the high costs and the benefits. Fixed grids and gratings and, increasingly, behavioural screens are also used and generally the principle of Best Available Technology Not Entailing Excessive Cost (BAT/ BATNEEC) is applied. In some circ*mstances it is possible to use fish friendly turbines or dams, however it is important to demonstrate beforehand that the required standards for survival rate can be reached. In some circ*mstances it is not considered possible to use the screen spacing required, or a screen may not be technically feasible. In these cases protection of fish should be reached by other measures such as fish friendly management of the turbines, although this may not be as effective.

Photo: The Drentse Aa, a lowland brook in the Northern part of The Netherlands.


Title Author Organisation Country

Fish migration in the lower part of the River Morava D. Veselý Povodí Moravy, s.p., Brno Czech Republic

Introduction Even though the first documented fish passes in the Morava river basin date back to 1932, the construction of fish passes since has been rare and the efficiency of those built has caused some concern. The change of the political system in 1997 brought renewed efforts to address problems for migration. The key project on the Southern Morava river was the international project Phare PEC No.85.320031, EU OSS No.98-5154.00 „Restoration of Fish Habitat and Hydrological Conditions of the Lower Morava/Dyje Rivers“, implemented in the years 1997-1999 and defining the basic aims for fish migration within the region. On the basis of this document and similar documents implemented in other regions, the Ministry of Agriculture of the Czech Republic issued the “Action Plan of Construction of Fish Passages for Major Migrating Fishes on Selected Rivers of the Czech Republic” in 2000. In the Southern Morava region the plan seeks to resolve the potential for migration of the spinal rivers Morava and Dyje. The measures will enable migration of the original fish species of the Black Sea basin in the Czech Republic.

Fish population and fish migration The fish population of the Lower Morava and the Lower Dyje rivers includes 13 fish families and over 50 fish species, thus representing the most diverse fish population in the Czech Republic. The species are characteristic of the Danube river basin and the Black Sea basin and are typical of the alluvial bank zones of the lower rivers and adjacent flood areas of these rivers. Unlike the majority of the Czech Republic, this area is not dominated by salmonids, but by other species with less ability to ascend obstacles. The purpose of the measures in the plan is to: • Allow for migration of the genetically original fish species from the main reaches of the Danube (including small sturgeon (Acipenser ruthenus), danubien perch (Zingel zingel), eastern zander (Stizostedion volgense), Pelecus cultratus and pearly shiner (Abramis sapa) and to improve conditions for protected fish including the orfe (Leuciscus idus), the wild form of carp (Cyprinus carpio), Pelecus cultratus, pearly shiner (Abramis sapa), launce (Misgurnus fossilis), Cobitis elongatoides, etc.; • Allow fish to reach the river reaches where flood plain habitat suitable for phytophilic fish spawning, including northern pike (Esox lucius), rudd (Scardinius erythropthalmus), tench (Tinca tinca), white bream (Abramis bjoerkna), crucian carp (Carassius carassius), carp (Cyprinus karpio), catfish (Silurus glanis), bass (Perca fluviatilis) and zander (Sander lucioperca).; • Allow other fish to reach lower river sections suitable for spawning of litophillic fish including chub (Leuciscus cephalus), barbel (Barbus barbus), beaked carp (Chondrostoma nasus) and asp (Aspius aspius).

The Elbe and the Odra rivers and, via the Danube, the Morava and the Dyje rivers drain to three seas. These are the North Sea, the Baltic Sea and the Black Sea. These rivers are the routes for entry of migratory fish to the Czech Republic. The purpose of the Action Plan is to provide passage routes for fish along the main spinal rivers and thus to allow the return of the endemic fish species to our territory and to provide acceptable habitats for their existence here. Implementation of the Action Plan should contribute to the creation and maintenance of biological diversity of ichtyo-fauna in the Czech rivers.


The first stage of constructing fish passes on existing river structures focuses on facilitation of fish migration at the existing structures on the main Czech rivers. The migration plan seeks maximum migration permeability through provision of passes on all newly constructed river structures and at largely reconstructed current structures. Designs emphasize the required connectivity of the rivers with their flood plains.

the weir pillar or within the weir adjacent to the banks. Since 1997 this has radically changed and the preference now is for nature like constructions, mainly boulder ramps located within the river bed or within a weir bypass. In some cases these fish passes are complemented with long bypasses of the weir using old river arms within the flood plain. Proposals are combined with overall revitalisation of the flood plain and creation of space for natural reproduction of fish, thus providing permanent and holistic solutions for fish.

Most fish passes constructed before 1997 are technical pool passes and are located within

Map: Classification of Czech rivers according to migration permeability.


Title Author Organisation Country

Approach to the restoration of fish migration in the lowland rivers of Flanders Saar Monden & Johan Coeck The Flemish Environment Agency, Water Department, Brussels & Research Institute for Nature and Forest, Brussels Belgium

The restoration of fish migration is based on targets set under the Benelux Decree M 96(5) of 26 April 1996 and is to provide free migration by 1 January 2010. This target is implemented in the “Flemish Decree Integrated Water Management”. In order to organise the realisation of a free migration in Flanders a strategy was developed. Watercourses in contact with the sea as well as the watercourses with greatest value and strategic importance are tackled first and a network of priority fish migration routes was identified, comprising 3,000 km of the existing 20,000 km of watercourses. (Monden et al., 2001). The obstructions to fish migration on these rivers have been integrated in a database, which can be consulted via www.vismigratie.be and based on this different water managers worked out a financial plan and an action programme for the restoration of free fish migration.

Together with The Netherlands we have established a method to identify efficient solutions for fish migration (Kroes & Monden, 2005). The measures consist of weir (v-shaped), pool (major part) and nature like bypass channels. Fish migration issues and solutions are also set out in long term ecological visions for each river. The realisation of fish migration on prior routes and the ecological visions are implemented in basin management plans. Communication between all water managers (communities, provinces, Flemish Government and organisations responsible for navigable waterways and smaller rivers) is made more efficient by the development of a Flemish law dealing with Integral Water Management. This law resulted in the so-called CIW (Co-ordination group for

Map: Overview of priority waters in lowland rivers of Flanders


integral water management) bringing together all relevant organisations within this framework. This law specifies also that for each Flemish river basin a basin management plan has to be made each 6 years, containing a detailed geographical vision and policy. CIW has different working parties, discussing various topics including one for ecological water management including a fish migration topic. Communication and education concerning fish migration is delivered through organisation of symposia, a yearly organised practical course for water managers on fish passage devices, a website: www.vismigratie.be and a manual. Communication with the public is achieved through meetings, events and through publication of

Water category

• • • •

Navigable Not navigable, category 1 Not navigable, category 2 Not navigable, category 3


papers and magazines. The government provides information points at many fish passes.

Photo: Fish pass Velpeph.

Length priority waters (km)

Amount of bottlenecks

Amount of solutions

Amount of solutions (%)

958 728 956 262

49 204 449 103

0 36 57 2

0% 18% 13% 2%





Table: Overview of fish migration bottlenecks and solutions in Flanders, Belgium (January 1th 2006).



5. Solutions for hazards and obstacles Solutions for fish passage change over time as knowledge and technology move on. Frequently, fish passes may prove to be effective but not necessarily efficient. Lessons need to be continually learnt from their failings and improvements made to try to maintain the most effective and efficient passes. For example, one of the first recorded fish passes in the UK was a wooden fish ladder that was constructed in 1864 on the River Ouse at Linton-on-Ouse. Either because it perished or else did not work, it was replaced with a ‘tunnel’ in 1877. However, the tunnel was rapidly scrapped in 1878 because it proved too steep for the fish to use. It was then replaced with a Home Office (government) approved pass in 1886 (approval first became required by law in 1883), but was once again reconstructed in 1899 at a cost of £547 because the previous one was considered to be of poor design. In 1921 it had to be further modified when a hydropower plant was constructed at the site, resulting in raised upstream water level. It was then modified again in 1936 to improve the location and attraction of the downstream entrance, which had been compromised by the conflicting lead caused by flow from the turbine draughts on the opposite bank of the river. Clearly there were problems at this site and indeed the pass is now likely to be modified yet again when a new hydro development takes place as the existing pool & traverse pass no longer meets current design guidelines.


Examples of fish pass systems in Europe

Fish ladder at Pitlochry dam, Scotland.

Fish pass in Cardiff Bay Barrage, Wales.

Fish pass in the River L’Isle, France

Fish pass in the River Ter, Catalonia


Merikoski fish way, Finland (Photo: J. Erkinaro).

Fish pass in the River Vecht, The Netherlands.

Fish pass in the River Dyje, Czech Republic.

Fish pass in the small River Ittersebeek, The Netherlands.


Title Authors Organisation


Merikoski fish pass in the River Oulujoki A. Laine1 & J. Erkinaro 2 1 North Ostrobothnia Regional Environment Centre, Oulu 2 Oulu Game and Fisheries Research, Finnish Game and Fisheries Research Institute, Oulu Finland

of the river came from local level. Even though fishery values arising from opening the migratory route were not considered very important, there were other values e.g. increased valuation of the river, the potential for small-scale natural production and stimulating other actions aiming towards an improved river environment.

Introduction The Merikoski fish way is a successful design in connection with the hydropower station of Merikoski in the mouth of the River Oulujoki and the heart of the city of Oulu with some 150.000 inhabitants. The river (catchment area of 23.000 km2 and mean flow of 265 m3/s) is heavily exploited for hydropower production. There are 7 power stations in the 100 km reach of the main stream between the river mouth and the central lake Oulujärvi and a total of 18 stations in the whole river system. The free passage of fish from the sea into the river has been blocked for nearly 60 years.

Prior to the construction decision, fish behaviour was studied in the area and the optimal location for the entrance of the fish way was suggested (Laine & Kamula 2001). The fish way was constructed in 2003. Its total length is 750 m with a rise of 11 m. The lower section at the powerhouse, with two alternative entrances, is located inside an old bundle-driving channel and the upper section at the regulating dam. In between these sections, a route has been excavated into the old river channel, in which the water level is maintained by means of a weir. The route aids fish in finding the entrance of the upper section and can be regarded as one part of the fishway.

Compensating the losses caused by damming, migratory fish have been stocked annually, mainly into the river mouth area. The initiative for allowing passage of fish into the lower parts

Photo: The lower part of the Merikoski fish way (J. Erkinaro).


The upper and lower parts of the fish way consist of vertical slot, Denil and semi-natural sections. Fish can be observed through a window in a control room at the upper end of the fish way and there is also a fish counter.

without delay to the next dam. Both the proportion of fish using the fish way and their behaviour reflected the stocking practice in this area. Most of the potential spawning areas are situated in two tributaries which, however, need restoration measures and even liming to ensure salmonid production. It is possible to create a limited number of habitat areas and fishing sites within the regulated main river reach e.g. by constructing deflectors. To ensure the efficient use of potential reproduction areas, stocking of salmon and trout should be directed to the best habitats.

Results So far salmon, trout, rainbow trout, whitefish, perch, pike, burbot and bream have been recorded in the fish way. Various other cyprinids and river lamprey use the fish way as well. In 2004, the first summer of full operation, 441 salmon, 265 trout, 26 rainbow trout and hundreds of other fish migrated through the fish way.

A new project, funded by the Euregio Karelia neighbourhood program, started in 2006. This Oulo project aims to find out the biological, juridical and social preconditions and impacts of constructing fish ways into the other dams of the main river along with general plans for fish ways to the migratory obstacles. The results can be used in other heavily constructed river systems.

The largest salmon weighed 18 kg. In connection with the introduction of the fish way, a survey was started in the river stretch between the Merikoski dam and the successive Montta dam, 37 km upstream (Laajala et al., 2006). Some evidence on salmon spawning was gained and, based on radio telemetry, most salmon and trout were found to swim

Map: The Merikoski dam and different parts of the fish way (Drawing: AirIx Terttu Kurttila).


5.1 FISH MIGRATION FACILITIES; STATUS QUO 5.1.1 Upstream facilities for fish migration Fish pass facilities to maintain upstream migration of fish, principally salmon and sea trout, have existed since the 19th century in Europe. In countries like UK, France and Finland earlier fish passes are known including some from the early 19th century and other even earlier fish passes have been reported. Some of the earliest passes were ineffective, largely because of poor construction and insufficient maintenance of the facilities and this occasionally resulted in a change of focus to financial compensation for damage to stocks or to fish stocking.

an impact of the structure on which they are built remains. Neither do they, of course, represent additional habitat for fish. The main problems in constructing upstream fish pass facilities are largely financial although in some cases, for example in highly populated areas or at high-head hydro-electric dams such as the 170 m high hydro-electric dam at the Nestos River in Greece, the problems are technical. Precedent of effective fish passes is always helpful but sometimes socio-political difficulties may still be difficult to overcome. For example in Greece it is still very difficult to convince decision makers and politicians that a lot of money needs to be invested in restoration of fish migration.

Most attention was on the large or long distance migratory fish such as the European eel (Anguilla anguilla), salmon (Salmo salar), sea trout (Salmo trutta) and in some countries the sturgeon (Acipencer spp., Beluga spp.). This was clearly due to the high economic value of these species to angling or professional fisheries and often also because these species were protected by law. Protective legislation in the UK, for example, is known from the 14th century.

The large number of obstructions, occasionally in excess of a thousand in some rivers means that much of the problems for realising fish migration facilities lies with finding sufficient funding. Technical and semi-natural fish passes are expensive and this means that in many cases it may be possible to build only a small number each year. For example in the UK (England & Wales) about 50 passes have been built in the last five years, compared to an estimated total requirement of about 5,000). Partly because of this slow rate of progress, many River Trusts and other partnerships have been set up by user groups to raise funds and make improvements including fish passes either independently or in collaboration with the Environment Agency (the modern Government regulatory authority).

New requirements to provide free passage for fish to fulfil ecological targets and as part of habitat restorations, together with an era of intensive fish pass research based on field testing and small scale fish pass models (Denil, 1909; Price-Tannat, 1938; Aitken et al., 1966; Larinier et al., 1992; Clay, 1995; Pavlov, 1989; Gebler, 1991; Boiten, 1989 & 2005; Kamula, 2001) quickly lead to many variants of technical fish passes. Nowadays pool passes are common mostly pool and traverse (plunging flow) or pool and weir (plunging flow mostly). In the 1970’s - 1990’s Denil passes became common and in the last 10 years bottom baffle (Larinier super-active baffle) passes have also become common. Technical solutions such as these will, if correctly designed and built, allow fish migration but they do not in themselves directly contribute to ecological restoration, because

Photo: Ramp with pool structure fish pass in the River Wupper, next to the hydro power plant “Reuschenberger Mühle” in Leverkusen (Ingenieurbüro Floecksmühle).


Title Authors Organisation


A case study of a weir rehabilitation Enrico Pini Prato1 & Claudio Comoglio 2 1 Department of Forest and Agricultural engineering, University of Florence, Florence 2 Politecnico di Torino, Land, Environment And Geo-Engineering Department (DITAG), Torino Italy

is a 0,7 m high stone stilling basin: a notch (0,7 m deep x 1,0 m wide) was made to facilitate access for the ascending fish to the fish ladder immediately upstream. In addition, the notch concentrates the discharge of the Comano in a single point, attracting fish from the Sieve River into the facility.

Introduction The case study is on the rehabilitation of an existing weir on the Comano Torrent, at the confluence with the Sieve River (Tuscany-Florence, Italy), located in the Tosco-Laziale district. This is an area characterized by a typical Mediterranean regime, where the watercourses have a discontinuous hydrological regime with frequent high-flow events in winter and extremely low water situations during summer. The more relevant endemic species are cyprinids whose breeding season partially overlaps with low flow conditions. As an approach to the problems, a pool and weir fish pass was designed, built and tested with a discharge of 50 l/s to correspond to the very low water flow during the cyprinid breeding season.

The fish pass is of the “pool and weir” type, with 7 pools, each separated from the next by a sluice gate with an orifice (0,1 m x 0,1 m) at the base and a lateral slot (0,5 m deep x 0,1 m wide) at the top. The pools are made of concrete and stone and there is a 0,3 m head drop between each one. The iron sluice gates have handles for easy extraction for cleaning and maintenance. The pools measure 1,25 m (length) x 0,9 m (width). The maximum depth measured on the sluice gate is approximately 1,1 m downstream and 0,8 m upstream and the slope of the bottom is 24%. All the pools have the same volume (1 m3).

The fish pass was designed and built specifically for the rheophilic cyprinid species, i.e. the barbel (Barbus sp.), the soufie (Leuciscus souffia), the chub (Leuciscus cephalus) and the roach (Rutilius rubilis). For optimal effectiveness, the fish passage was calibrated to the typical water levels of the Comano during the period of April to June when rheophilic cyprinids migrate to breed. The upward migration of the eel (Anguilla anguilla) and the brown trout (Salmo trutta) were also taken into account in the design. The fish pass was built in April 2002 and it is now a fieldwork and educational site, with an information display board to raise public awareness on local fish life and on the importance of the fish pass (www.passaggiperpesci.it). The weir is 22 m in length and there is a drop of 2,3 m in low water periods. About 10 m downstream there

The upstream exit is screened by a metal grille to prevent floating debris from blocking the pass. The downstream entrance is set on the side of the weir to guarantee a proper at-

Photo: The Comano Torrent fish pass.


traction flow for the fish approaching the obstacle and to avoid their disorientation due to the turbulence. The dimensions of the facility are designed for an optimum flow of 50-60 l/s with energy dissipation in the pools of approx. 165 W/m3. This quantity of flow can generally be expected even in dry periods and can be relied on in the migrating season (data from the Province of Florence), though there are fluctuations and the figure is approximate. In any case, the facility is designed to work with flows in the range of approximately 30-80 l/s.

Photo: Barbel (Barbus Plebejus).

Monitoring and results There was an initial observation phase in 2002 during the start of the spring reproductive season and then two phases of three days each involving specimen capture; one in late spring and one in summer (Pini Prato & Nocita, 2004). The specimens were collected in a fish trap. In the experimental phase in June, the flow rate measured in the fish pass was 65 l/s during the first two days, when there were stable weather conditions. On the third day, following a violent thunderstorm, the flow increased rapidly to 80 l/s, with energy dissipation in the pools estimated at approx. 190 Watt/m3. On that day, 13 specimens were recovered from the fish trap. Some of the captured barbel were incontrovertibly in a reproductive state as demonstrated by the fact that while handling for measurement they released eggs or sperm.

Photo: Sofie (Leuciscus Souffia).

Photo: Arno Goby (Padogobius Nigricans).


Title Author Organisation


State of the art of fish connectivity in the Catalan rivers Marc Ordeix CERM, Centre d’Estudis dels Rius Mediterranis (Center for the Study of Mediterranean Rivers), Fundació Museu Industrial del Ter (Foundation of the Industrial Museum of the Ter River), Manlleu Catalonia, Spain

A first step to improve fish connectivity in Catalonia is to take place during 2006-2008. Following assignment from the Catalan Water Agency, the CERM has produced a map of fish connectivity grades, in five colors, following the Water Framework Directive (2000/60/CE). The map also indicates future fish passes within the project and sets priorities for each. There are currently around 30 fish passes in Catalonia, the oldest from 20 years ago.

will support ecological targets to be set for the Water Framework Directive (2000/60/CE). The eel (Anguilla anguilla), the most important migrating fish species in Catalonia, is critically endangered. In estuarine areas there are also: shad (Alosa fallax, Alosa alosa), sturgeon (Acipenser sturio which may now be extinct) and sea lamprey (Petromizon marinus). All other migratory species are endangered or need help, moreover the knowledge of Iberian fish ecology generally is quite incomplete (Elvira et al., 1998; Doadrio (ed.) 2001; Sostoa, 1990). In the Ter River basin and all others in the Northeast of Catalonia (Besòs River, Tordera River, Fluvià River, Muga River and different litoral creeks), 4 species: eel (Anguilla anguilla), common trout (Salmo trutta), mountain barbel (Barbus meridionalis) and bagra (Squalius cephalus) are present.

The majority of these do not work well and unfortunately even the best have some problems. In the first year of study (2006) we monitored the effectiveness of two fish passes in the Ter River (NE Catalonia), one at Torroella de Montgrí (low part) and the other at Camprodon (high part). The CERM will continue by monitoring four extra fish passes from different Catalan basins until 2008 and will then be able to propose solutions to improve fish migration in the whole of Catalonia. The improved knowledge of the current state of fish connectivity for migratory species and also improved understanding of non-migratory in the Catalan rivers

Restricted to estuarine areas are the shad (Alosa fallax), bass (Dicentrarchus labrax), vera mullet (Chelon labrosus), calua mullet (Liza ramada), little mullet (Liza saliens), sea-perch mullet (Mugil cephalus), fry (Atherina boyeri) and flounder (Platichtys flesus). In the Ebro River basin and others from the Mid-west (Llobregat River, Foix River, Francolí River and different litoral creeks), 6 species are present: eel (Anguilla anguilla), common barbel (Barbus graellsii), red-tailed barbel (Barbus haasi), common trout (Salmo trutta), madrilla (Chondrostoma miegii) and bagra (Squalius cephalus). In the southerly part of Catalonia, notably the Ebro River delta, there is an intensive eel fishery, both for adults but principally for glass eel. Eel stocks here, as elsewhere, are falling year per year.

Photo: Fish ladder at Torroella de Montgrí (el Baix Empordà) bridge.


Title Author Organisation


River protection system and fish migration in Lower Saxony C. Lecour Lower Saxony Federal State Office for Consumer Protection and Food Safety & Institute for Ichthyology, Department for Inland Fisheries, Hannover Germany

In Lower Saxony a river protection system has been established since 1989, referring to selected watercourses (connecting streams comprising main and smaller tributaries of first or second priority, referring to their regional importance for the conservation of aquatic habitats, flora and fauna). One of several manifested intentions of the RPS is to enable unhindered fish migrations within these watercourses by removal of migration obstacles or building of fish ways.

proprietor of the weir), are often supplemented by means of the EC. Funding arising as an obligation for licences in the context of permissions of hydro-electric power stations is also used to build fish passage facilities at weirs in navigable waterways within Germany.

Funds of Lower Saxony mostly from the so called “Fließgewässerschutzprogramm - Programme for protection, restoration and management of running surface water” (if the federal state is

Map: Hydro-electric power station at Hannover-Herrenhausen (plan view).


5.1.2 Downstream facilities for fish migration Problems with downstream migration of fish in Europe have largely been acknowledged only quite recently. With downstream passage the issues are slightly different in that many obstructions are easily passable in the downstream direction, which is very different to the situation with upstream migration. The exception to this is of course when the obstructions support abstractions into which the migrants might be entrained.

most efficient techniques available appear to be physical barriers, behavioural solutions remaining largely experimental due to their current low rate of reliability. It appears that a satisfactory solution has not been devised and this is particularly the case for large hydropower plants (Larinier, 2001) where extremely high rates of fish may occur. Behavioural exclusion systems have varying degrees of success and are often critically dependent on the location and precise operation of the device. In the USA studies are undertaken to adapt turbine design for fish migration (Cada et al., 1997) so that passage through the hydropower plant itself may not be damaging. It remains the case that effective facilities for downstream fish passage are not yet in place and that further research is needed.

The increasing demand for low-head hydropower, due to rapidly emerging demands for sustainable and renewable energy, is a potential problem for fisheries. Similarly the requirement for screening protection of intakes frequently destroys the economic case for the scheme. The provision of adequate screening and bypass facilities is a legal requirement in some countries, such as the UK and in many cases it can represent an economic challenge.

5.2 FISH PASS DESIGN AND CONSTRUCTION; A THREE-STEP APPROACH This section describes the approach to resolving upstream and downstream migration problems at a range of structures. The section is largely based upon existing manuals for restoration of upstream fish migration (Armstrong et al., 2005; Larinier et al., 2002; Kroes & Monden, 2005 etc.) and for downstream migration (O’Keefe & Turnpenny, 2005; DVKW, 2002; ATV DVWK, 2004, Turnpenny et al., 1998a). The reader is referred to these manuals for further information.

Effective fish protection facilities are often much more difficult and complex than facilities for upstream fish migration. Although the problems for downstream migration when abstracting water for mills, channels, hydropower, for commercial use e.g. cooling water or for potable supply etc. are recognised in most European countries, experience with resolving the problems appears to be largely restricted to Germany, France and the UK. In these countries and in North America problems with downstream migration have been thoroughly examined for anadromous species, in particular salmonids and eel (Larinier, 2001). Little information is available for other species, because until recently there was little concern for them.

Each step is discussed in this chapter, including the identification of need, the starting points and the principles. It should be noted that some solutions for hazards and obstacles may apply in both upstream and downstream direction. This means that every solution ought to be studied in an integral way. Although a solution that works in both ways is preferred, in some cases discrete solutions for upstream and downstream migrants may be required. Therefore every step deals with upstream and downstream migration separately.

Nowadays a large number of systems exist to prevent damage caused by water intake at hydro-electric power stations. Downstream facilities generally consist of physical screens and/or behavioural exclusion systems. The


Title Author Organisation Country

Eel protection programme Luxembourg M. Lauff1, A. Hehenkamp 1 Administration de la gestion de l’eau, Service pêche, Luxembourg (Grand-Duchy) Luxembourg

Introduction The “Luxembourg Eel Protection Program” is a feature of the Rosport hydro-electric power plant operation at the millrace near Rosport, Luxembourg. The millrace is fed by a storage lake in the River Sure, which marks the border between Germany and Luxembourg in this area. The power plant can work up to 70m3/ sec; the average amount of water in the Sure is about 10-15m3/sec in summer and about 50m3/sec in winter. The eel protection program started in the year 2004 and was developed because every year the public along the Sure downstream of the Rosport power plant took notice of large amounts of dead silver eel. This phenomenon usually occurred in the beginning of autumn every year.

net (in German, a “Hamen”). This net is used, when the main migration is underway in the months October-January and after significant increases in flow in the summer. It is fished predominantly at night. During the first season the trial was run during dark moon phases, but without a rise in flow there were no spectacular catches. The Hamen almost closes off the complete millstream and leads the eels to a tail with a net-lock (cod-end), from which they cannot escape. This method works very well during phases with strong current and colder water, when silver eel appear to drift downstream. In the first year, after resolving seve-ral technical difficulties, about 80 eels were caught by the Hamen and 300 by the fyke nets. In 2005 the Hamen caught about 480 eels; the best catch in one night being over 300. The fykes caught about 500 eels from May to November. In the night on which the Hamen caught 300 eels the fykes only caught 4, whilst the following night with comparable conditions the Hamen failed because of a large amount of drifting wood. The fykes only caught 3 more eels that night.

The fundamental idea of the eel protection program is to catch as many eel as possible before turbine passage, which was concluded to be the reason for damage and mortality of eel. A second objective was to learn more about silver eel migration, their abundance and the environmental triggers that initiate migration in the Sure. The eel was caught by two different fishery methods. Firstly fyke nets were placed at varying different distances upstream from the turbine intake. This method was considered to catch those eels that reverse their downstream migration as an escape reaction following initial approach to the intake screen. The fyke nets were retrieved every day from May to December. This method was found to work very well in the warm part of the year, i.e. during the months May to October. Monitoring and results As a second capture method a special net was constructed, which works similar to a Schokker


The basic steps consist of: Step 1.


Features and conditions: • Hydrological and hydraulic factors; • Financial or legal requirements; • Geology and geomorphology; • Section profiles, substrate, type and amount of debris. Target species: • River zone; • Fish species present, including reference to WFD. Choice of the specific solution (what facility will achieve the ambitions): • Solution for combined up- and downstream functioning; • Upstream migration facility; • Downstream migration facility.

Step 2.


General design criteria: • Biological criteria for target species; • Hydraulic criteria. Specific design criteria: • See different technical manuals. Licence and permits: • Arrange permits and licences which are needed to built a construction.

Step 3.

Construction and maintenance

Last check on design: • Biological and hydraulic criteria. Coordination of construction: • Biologist and engineer. Protocols for maintenance: • General description of operation of facility; • Period; • Frequency; • Required methods/materials; • Health and safety issus.



Step 1. Definition Target species Target species can be identified on the basis of river typology studies, on zoning according to Huet (see paragraph 2.2) or simply on the known assemblage of species. The choice of target species will determine the design (e.g. size, drops and minimum depth) and location of a fish pass. Every fish species has its own characteristic swimming capacity and typical behaviour. The swimming capacity depends on morphology, condition and length of the fish species and the water temperature during their migration. Behaviour of fish is variable on a seasonal and daily basis and depends on a wide range of factors including shore or depth orientation during migration, residence and response to hydraulic parameters and light.

The definition study comprises a study of local features and conditions, target species and outline choice of the specific solution. It is very important that the different disciplines (ecology, hydrology and engineering) work closely together at this stage to achieve an optimal solution. 5.3.1 Upstream fish migration Solutions for hazards and obstacles depend on the site and nature of the river and the target fish species. Some types of migration barriers are specific to certain areas or are characteristic for water types. Therefore 4 different river types are distinguished here; rivers and streams in highlands, rivers and streams in lowlands, coastal zones and flatlands. Each river type is characterised by the presence, sometimes temporal, of specific groups of fish species. This is discussed in paragraph 2.2.

Choice of solution Technical solutions to secure fish passage past an obstruction are variable called fish ways, fish passes or fish ladders. The principle is to attract migratory fish to a specified point downstream of the obstruction and to allow them to pass upstream by providing a route in which water velocity and turbulence is both attractive and within the fishes swimming abilities. Passage can be secured by removal of the barrier, reducing the barrier or through installation of mechanical devices that help fish to migrate upstream. All measures can be categorised in order of preference: • Natural solutions (restoration of the natural situation, for example dam removal); • Semi-natural solutions (fish passes that provide both a nature like route for fish and habitat); • Technical solutions (technical constructions like baffle or pool and weir fish passes, eel ladders or fish lifts); • Adjusted or alternative management (alternative management of sluices or weirs to sustain migration).

Features and conditions For each site a description is needed of the local features and conditions so that an optimal design might be identified. The selection can be determined by the long term plan or vision for the river basin, characteristics of the surrounding area and legal, hydrological, biological and financial aspects. The critical questions to be answered are: • What are the target species and at what time of the year do they need to migrate? • What is the structure and function of the obstruction? • What are the seasonal flow rates what might be the limitations on the amount of flow that can be used for the fish pass? The vision for the river basin and, specifically, for the river is central to the strategy to improve fish passage opportunity.


Based on an assessment of local features and conditions (e.g. type of water body, target species, land use etc.) and the financial scope for action, the optimal passage solution for a migration barrier can be identified.

as well as the benefits is important, particularly if there are any river bank structures close to the proposed works. Ideally, weirs that no longer have any function should be removed, however this is rarely the case in practice. Happily, ecological awareness is gaining, notably in Spain where legislation permits the removal of dams that can be demonstrated to have lost their original role, however it is still the case that removal of superfluous weirs does not happen. The Spanish precedent is perhaps one that should be explored elsewhere, particularly within the context of the WFD. When it is not possible to completely remove the barrier, it is preferred to approach the natural situation as close as possible perhaps by lowering the crest height of the dam.

Ad 1. Natural solutions The optimum ecological solution for maximum fish passage efficiency is clearly the complete removal of the structure. Weir or dam removal restores the natural situation at that location allowing natural dynamics and channel structural diversity to recover. This solution is preferred because not only is migration in the longitudinal and lateral direction restored, but also local habitat is restored. A feasibility study to identify potentially negative factors, such as local bank erosion and bank stability matters,

Natural solutions



Removing weirs/ culverts e.g.

Small constructions that are removed, subject to local river management review.

Small streams and brooks, occasionally larger rivers (low and high head)

Removing weirs in combination with meandering/habitat restoration

The removal of weirs or dams often needs to be combined with lengthening the stretch of the river, in order to manage flow velocities and restore natural meandering.

Lowland rivers

Removing dykes and restoration of floodplains

When dykes are (re)moved natural floodplains are connected with the rivers in periods of high water levels.

Polder, reservoirs, larger lowland rivers

Restoration of estuaries

Restoration of estuarine character can be achieved when tidal sluices are removed or permanently opened. Full hydrological, saline and sediment regimes can be restored.


Table 5.1: Overview of natural solutions to restore upstream migrations.


Examples of solutions for fish migration Technical solution: Constructing Tube fish way at pumping station Roptazijl, The Netherlands.

Technical solution: Vertical slot fish way in the River Taff, Wales.

Semi natural solution: Rock ramp fish pass in small river Smallertse Beek, The Netherlands.

Semi natural solution: Cascade fish pass in the River Sieg, tributary of the River Rhine, Germany (Photo: E. Winter).


Semi natural solution: Fauna passage Silkeborg.

Technical solution: Fish lift at pumping station Rozema, The Netherlands.

Technical solution: Vertical slot fish way in the River Leine, Germany.

Semi natural solution: Cascade fish pass in small river Oude Diep, The Netherlands.


Title Authors Organisation


Nature-Like Bypass Streams functioning as stream habitats J. Jormola1, L. Järvenpää1 & T. Hakaste 2 1 Finnish Environment Institute SYKE, Helsinki 2 Hämeen TE-keskus/The Economic and employment centre of Häme, Hämeen Finland

Regional Environment Centre, consists of five rocky ramps, height 2,0- 0,8 m within the old river channel, and a 320 m nature-like bypass stream at the regulation dam. The required base discharge 0,5-0,9 m3/s is flowing through the fish pass into the old river, occasionally also 200 m3/s flood through the regulation dam. In the bypass stream gravel beds are constructed, to enable spawning. To maximize the production capacity and refuges for juveniles, stones and woody debris are placed into the bypass. Migration and reproduction of trout and salmon are monitored.

Nature-like bypass streams are nowadays preferred as fish ways in Finland (Jormola et al., [eds.] 2003). When constructed beside existing dams they resemble natural cascade or step-pool type stream morphology. Even steep nature-like bypasses up to slopes of 1:10 have proved to function for almost all northern fish species. An advantage is that even weak swimmers and bottom fauna like crayfish can use them because of diverse bottom structure and flow heterogenity. Some old dams or weirs have been replaced with rocky ramps or artificial rapids within the channel, enabling floods to flow over the structure. Most nature like bypasses have been built in the regions of Uusimaa and Häme, Southern Finland. In most cases the fish passes are built as a part of larger river restoration plans, in order to strengthen weak natural brown-trout or sea-trout stocks. In Häme region a special construction principle has been applied, using loose stone material. Several alternative migration routes are formed within the channel and the solutions resemble a natural river.

Photo: Bypass stream at the Kaitfors powerplant dam, height 5,3 m, length 320 m, slope 1,7 % (1:60). Spawning gravel has been installed into riffles. Cost: 50 000 euro. (Jukka Jormola).

Recently one aim in constructing nature-like bypass streams has been to combine the need of migration with the need of constructing new reproduction habitats in the bypass stream itself. This is important in heavily modified rivers, where natural reproduction areas have vanished through power plant construction and elevated water levels.

Photo: Constructed bypass stream with several migration routes in Häme area (Auri Sarvilinna).

The fish pass at Kaitfors power plant in Perhonjoki River, constructed by the West Finland


Ad 2. Semi-natural solutions If it is not possible to fully restore the natural situation, then a semi-natural solution can be chosen by creating an artificial, though naturelike, channel around the weir. These can partially resolve fish migration issues whilst also

contributing extra habitat or holding areas for fish species. The barrier remains in place and the risks of bank stability problems therefore do not arise. It should be clearly noted that it is the provision of a route for free fish migration that takes priority.

Semi-natural solutions



Nature like bypass channels

A natural waterway that bypasses the river from upstream of the obstacle to downstream. The waterway is similar to the natural situation and therefore provides some potential habitat as well as restoration of fish migration.

Brooks and rivers

Pool-riffle fish ways

Higher gradient stretch with large stones placed in a zigzag arrangement to create a pool and riffle structure. It is also possible to use large wooden structures.

Brooks and rivers

Riprap; rock ramp fish ways

Relatively high gradient stretch with large stones randomly placed. This solution appears as a natural rapid.

Brooks and rivers

Step-pool; cascade fish ways

Relatively high gradient stretch with rows of stones placed over the whole width, forming cascades. It is also possible to use large wooden structures.

Brooks and rivers

Restoration of tidal exchange

With management of tidal sluices it is possible to restore tidal exchange inland with opportunity for fish passage. This is possible in the river and in an area adjacent to the river by means of a culvert. A permanent fresh water supply is needed.


Restoration of temporal flooding areas/wetlands

Temporary controlled flooding areas by pumping water onto the floodplain or by allowing floodwater to accumulate.

Polders, floodplains and reservoirs

Table 5.2: Overview of semi-natural solutions to restore upstream migrations.


Title Authors Organisation

Fish passage facilities in Hungary G. Guti and M. Pannonhalmi Sturgeon 2020 Deposit Company in Györ, Hungarian Danube. Research Station of the Hungarian Academy of Sciences, Göd Hungary


As a lowland country Hungary does not have many hydro-electric dams however there are thousands of small weirs without any fish passage facilities. A further problem is the extensive flood-protection dike system along the large rivers. Dikes divide the floodplains and about 90% of the original floodplains are now a flood protected area. Dikes restrict the lateral connectivity between the rivers and their floodplain water bodies. Drainage sluices and agricultural water intakes in the extended channel systems of the protected floodplains usually constitute insurmountable barriers for fish.

The discharge of the Danube has been diverted to the bypass channel of the Gabcikovo hydro-electric power station since 1992. In consequence, a 30 km long section of the river was drained and connectivity of floodplain side arms was disrupted in the Szigetköz area. The Dunaliliti bottom sill raises the upstream water level to ensure water supply to the side arms and the structure is equipped with an upstream fish way. In 1995 the downstream area of the Dunakiliti bottom sill was equipped with a fish ramp. In 1998 a fish pass at Cikolasziget was built. The fish pass at Cikolasziget has two components: an upper section vertical slot fish way and a lower section near-natural channel. Its purpose is to provide appropriate passage for about thirty indigenous Danube fish species (Guti, 1996).

Sketch of the Denkpál fish pass.


Before implementation of the Szigetköz floodplain water replenishment system, we had to close the side arms because their water levels are several meters higher than the water level of the main channel. The new weirs in the tributaries are insurmountable barriers for fish. The fish pass at Cikolasziget provides a lateral migration route between the main channel of the Danube and the floodplain sidearm system.


Fish assemblages at the Dunakiliti bottom sill were surveyed occasionally by electro fishing and upstream fish migration was evaluated with a mark-recapture experiment in 19961997. The function of the fish pass at Cikolasziget was monitored from 1998 to 2002 and fish assemblages were investigated by electro fishing in the channel of the fish pass. Upstream and downstream (drift of fish) migration was evaluated using a special trap (Guti, 2002).


Ad 3. Technical solutions If it is not possible to achieve the objectives of free passage for fish through a natural or seminatural solution, than a technical solution (fish pass) is chosen. Formal fish passes can contri-

bute to securing longitudinal or lateral migration, but by their nature they do not contribute any extra habitat. Nevertheless they can resolve fish passage issues where more natural alternatives cannot be used.

Technical solutions



Pool fish way with overfall weirs

Fish way with pools that are separated by over falls. The weirs are usually notched to take low flows and can be designed to provide plunging or streaming flow to suit the fish species present. Sometimes the overfalls have a v-shape in order to concentrate water.

River, brook (relatively low range of water levels; usually low head drop)

Pool fish way with vertical slot

Fish way with pools that are separated by one or two deep vertical slots that reach from bottom to the surface. Can be combined with pool and weir fish ways or submerged orifice passes.

River, brook (low- and high range of water levels. Can cope well with high range of water levels)

Pool fish way with submerged orifices

Fish way with pools that are separated by submerged orifices.

Polder, river, brook (low head)

Tube and siphon fish way

This type of fish way can provide fish migration from the sea to inland waters that are below sea level. A tube and siphon fish way uses a pump to create an attraction flow and a vacuum pump transports the fish to the inland water level.

Polder, estuaries

Fish lock

Fish locks have the same principle as shipping locks.

River (high head)

Fish lift

The strategy of the lift is to attract fish to a water filled chamber at the downstream side of the obstruction (i.e., tailrace area) and lift them passively within a tank to the top of the dam for release.

River, brook, hydro-electric dam (can be high head)

Baffle (“Denil” or “Larinier”) fish way

Baffled fish ladders are relatively narrow chutes or flumes, usually no more than 1m wide for Denils but up to 5m wide for Larinier passes, within which steel or wooden baffles of varying

Brook, river (relatively low head)


design are located. The internal roughness created by the baffles disperses energy and reduces velocity to enable fish passage. Fish ways for eel/ elvers (eel ladders)

Special passes for migration of young eel and elver. They can be combined with fish ways for other fish species. These fish ways are based on the ability of eel/elver to climb and crawl when passing an obstacle. Materials can consist of branches, reeds, artificial brush or grass.

River, brook, polder, estuaries

Screw jack fish way

Its function is based on the same principle as the tube and siphon fish way. It uses a screw jack to pump up the water and create an attraction flow in the direction of the inland water below sea level (polders).

Polder, estuaries

Fish ways for culverts

A culvert is a connection between two water bodies, typically a pre-formed concrete tube located below roads or other constructions. In order to make a culvert passable for fish, the flow characteristics (velocity, water level and slope) are adjusted to mimic the natural river. It is possible to lower the culvert, in order to create sufficient depth for fish to swim, to place weirs or baffles in the culvert, or by replacing the culvert with a clear-span bridge. Migration of land animals, notably otter, should be taken into account.

Lowland brook, river (low head)

Table 5.3: Overview of possible technical solutions to restore upstream migrations.

Target species

Ad 4. Adjusted management Some barriers can be managed in a different way to enable fish passage to occur. There are several potential areas in which management can be adjusted. Often all that is needed is a good understanding of the times that fish wish to migrate and the flow and velocity characteristics that are conducive to this together with clarity on what can be delivered by management change. Adjusting management in this way can be an almost zero-cost solution and may in fact be superior to a formal fish pass as much larger attraction flows may be available.

Species like the Twaite shad (Alosa fallax) can profit from fish friendly lock management.


Title Authors Organisation Country

Solutions for culverts in Finland Anssi Eloranta1 & Jarmo Kovanen2 1 Central Finland Regional Environment Centre, Jyväskylä 2 T&E Centre for Central Finland, Jyväskylä Finland

In Finland many thousands of culverts exist, especially in the headwaters. They became very common in the forest roads, when the practice of timber-floating ended in brooks or streams in 1965. Typical problems of road crossings for aquatic fauna are insufficient water depth in culverts, clogging of culverts with rubbish and sediment, outfall barriers, excessive water velocity, lack of resting pools above and below culverts, harmful turbulent flow patterns and smothering by vegetation. We have tried to improve the knowledge of the general public on the problems of culverts and we have tried to seek the integration of stream ecological need into the planning, design, construction and maintenance of roads. It is easier to do the “right things” before and during installation of a culvert than after it. We also prefer bridges and single large, semi-circular culverts with natural brook-bottom to be used rather than round-shaped culverts and multiple small culverts.

Photo: Outfall barrier.

Finally, we try to restore wrongly-installed culverts, for example by cleaning openings of culverts, by building a series of low-head dams below the culvert outfall to raise the tail water level to facilitate fish entry, by preventing hazardous erosion close to the culverts and by decreasing water velocity in the culvert with stones.

Photo: Culvert replaced with a bridge.


Examples of fish friendly lock management

Lauwersmeer, The Netherlands

Nieuwe Statenzijl, The Netherlands

Adjusted management



Estuarine constructions (discharge sluices e.g.)

Fish migration can be achieved by opening the sluices when the difference in water level between the river and the inland water is low. The lower the velocity at this time, the more species are able to pass the structure. It is also preferable to allow sea water to intrude into the inland water during high tides.


Adjusted sills

Weirs that underflow can be passable when the water level difference is low and this facility should be provided, even though it may not last for long. Flow velocities are low under these circ*mstances.

Lowland brook, river (low head)

Shipping locks

Fish passage can often occur when navigation locks operate. This can be an important migration route and the option of locking through for fish, not necessarily with ships, should be explored. This is especially suitable when all of the waterway discharge passes the shipping lock. It is often less suitable when most water passes over an adjacent weirs, because most of the attraction comes from the weir, however even then the lock might still be a significant migratory route.

Waterways with navigation/ or used to have navigation

Table 5.4: Overview of possible ways for adjusted management to restore upstream migration.


5.3.2 Downstream fish migration Weirs and dams have been built over the last two centuries to support water abstraction for various purposes and to provide a head for hydropower generation. Although downstream migrant fish can safely pass over most of these weirs, the abstracting or generation processes can draw the fish into their intakes and cause serious mortality. If the rates of abstraction are high then fish mortality can reach serious levels. In all cases it is important to minimise entrainment of fish.

various formulae have been suggested to predict the mortality rate at Francis and Kaplan turbines in France (Larinier et al., 2002) and similar approaches have been developed in the UK (Turnpenny et al., 2000). These give general estimates of mortality rates and can be used in a predictive way to identify whether installations cause damage. More reliable data on mortality rates are gained by experimental field research (Berg, 1987; Haddering & Bakker, 1998; Pavlov et al., 2002), that can also indicate non-lethal physical damage to fish. Such studies can be very expensive.

Features and conditions Solutions to ensure safe downstream fish migration strongly depend on the local situation. For the planning of a facility for fish protection and guidance, information is required on the hydrological and technical features of the structure past which fish need to safely migrate and the way in which the site is managed.

In some specific situations it is possible that the spillway can function as a by-pass and surface bypasses located close to the abstraction screens can also be effective. The water distribution between the abstraction and the spillway is likely to influence the proportion of fish that pass over the spill way, however careful design of the structure has the potential to maximise escapement.

Important hydrological features are the daily rate of flow during the migration period and the proportion of this which is routed through a turbine or is otherwise abstracted. Other features include channel morphology in the vicinity of the abstraction, the depth at which water is drawn-off and flow rates and velocity patterns at that point, light and sound conditions underwater and the local occurrence and behaviour of floating or semi-buoyant sediment, debris and trash. Fish migration may occur at high flows and so local flow characteristics in extreme conditions is also relevant.

In the UK, all abstractions must be licensed and conditions are usually attached to protect migratory salmonids, coarse fish, eel and lamprey.

Relevant technical features of the water intake site include precise design and lay-out, the management protocol under the full range of flows and any technical and licensing conditions that constrain abstraction, including any environmental “hands-off” flows. The nature of the abstraction, including the type of any turbine, the hydraulic features and the fish species present will together determine the damage/ mortality rate. Although every site is unique,

Photo: Fish pass Breebaart, The Netherlands, provides a connection between the sea and polder Fiemel.


Target species With information described earlier, it is possible to decide what species should be protected at any abstraction point and this can guide selection of the best available facility for downstream fish migration. Target species are usually well known and are determined based on biological information and fishery records. Initial assessments may demonstrate that the requirements of some species may not be critical to intake and screen designs, for example if: • The fish specie is able to fulfil their life cycle in the available habitat and in connected side waters with no need to migrate; • The impact of the abstractions on the population is negligible; • The species have been extinct and have little chance of returning in the future.

fish entrainment, it should first be determined whether the objectives can be met by modulation of pumping or by resiting of the proposed intakes. If this is not possible then suitable facilities for protection of downstream migration should be chosen. The solution to protect fish through guidance and screening should be determined through a study of best practice (O’Keefe and Turnpenny, 2005) and known effectiveness of certain facilities for the target species. The most suitable for the site may then be selected taking into account all relevant riverine features. Facilities for downstream migration prevent fish from entrainment in the turbine intakes and guide them to a bypass that transports the fish downstream (Larinier et al., 2002). The principle is to guide fish towards the bypass taking advantage of, or through manipulating of hydraulic flow patterns, because fish tend to move with the current during downstream migrations. Different types of guiding and screening facilities exist and may be categorised into: 1. Mechanical barriers (that exclude fish from the water intake by a mechanical barrier, e.g. wedge wire screens); 2. Behavioural barriers (that guide fish downstream using some sort of stimulus e.g. sound, light);

The remaining target species should be protected, through combining sufficient ecological knowledge with best-practice technical solutions for bypasses, screens and for protected environmental flows. The justification for this expense is provided in some countries by domestic legislation but can also be supported by fishery economics and other social arguments. Choice of solution Prior to consideration of technical solutions to

Target species A Flounders (Platichthys flesus), B Ide (Leuciscus idus), C Salmon (Salmo salar) and D Sea trout (Salmo trutta trutta).






3. Bypasses (offer a alternative route downstream); 4. Adjusted or alternative management/other methods.

ble (Turnpenny et al., 1998a; O’Keefe and Turnpenny, 2005) for a wide range of sizes of rivers and abstractions. Passive Wedge Wire Cylindrical screens are considered to be the best method for exclusion of fish, with up to 100% effectiveness, however their usage for middle European rivers is limited to 10 m3/s.

Based on the information in step 1 and 2 (e.g. target species, technical and biological features) it is possible to choose a certain type of facility to protect downstream migrating fish at the site. In table 5.5 an overview is presented of facilities for safe fish passage downstream.

The use of an appropriate screen bar spacing is important if targeted protection is to be achieved whilst adverse impact on water abstraction is minimised. It is important to note that fast flows through any screen may still kill fish through impingement and it is important to avoid this.

Ad. 1 Mechanical barrier Many different mechanical barriers are availa-

Type of screen



Passive mesh screen

Difficult at large abstractions.

Salmonids and larger fish

Vertical/inclined bar racks


Salmonids and larger fish

Rotary disc screen

Rivers with a strong sweeping flow. Not for large intakes due to high surface area for desired flow velocities.

Salmonids and larger fish

Coanda screen

Spillway screen for new build small upland hydro intakes (or replacement of existing spill way screens).

Salmonids and larger fish

Smolt safeTM screen

Spillway screen for new build small upland hydro intakes (or replacement of existing spill way screens). Other types of application where sufficient head of water exists, e.g. fish farms on upland rivers.

Salmonids and larger fish

Band or drum screen

Estuarine and coastal power stations.

Robust epibenthic species (e.g. flat-fishes). Less suitable for pelagic species and sensitive species including salmon.


Passive wedge wire cylinder screen (PWWC)

Wide range of smaller abstractions (few m3/s) in fresh and marine water. Not suitable for low head hydro-electric power stations.

All species and sizes of fish given suitable wire spacing.

Small aperture wedge wire panel screens

Difficult at large abstractions.

All juvenile and adult of salmonids, lampreys, eel and cyprinids species.

Sub gravel intakes and wells

Small abstractions in fast flowing, eroding substrate rivers and is suitable for potable water or fish farm supply.

All species and sizes. May have a negative effect on the fish habitat.

Marine Life Exclusion System (MLESTM)

Industrial and power plant abstractions where the flow rate is in the range of 0,04-0,1 m3/s. Maximum 50 mm head differential.

Provides protection of early stages of fish.

Barrier nets

Mainly suited for large water bodies with low bio fouling and debris levels and where fish risk is seasonal.

Salmonid smolts and adults of most species.

Modular inclined screen

Application in upland areas. Negative is the large size and high costs relative to flow.

All juvenile and adult of salmonids, lampreys, eel and cyprinids species.

Self cleaning belt screens

Wide range of applications where a self cleaning fine mesh screen is required. The screen has been used widely in the USA for irrigation water intake.

All juvenile and adult of salmonids, lampreys, eel and cyprinids species.

Labyrinth screen

At large intakes or where space is premium and a compact screening arrangement is required.

All juvenile and adult of salmonids, lampreys, eel and cyprinids species.

Table 5.5: Overview of physical barriers for downstream migration.


Ad 2. Behavioural barriers The use of behavioural barriers, such as acoustic barriers, to exclude fish from abstraction channels or to guide fish to a bypass facility is usually only partially effective. This is because the avoidance behaviour they promote is variable between individual fish of each species and the precise point or onset of a startle or avoidance reaction may be critical to successful passage. Behavioural barriers are effectively speciesspecific and the protection of all fish species is therefore not possible.

In Europe promising results have been reported from experiments and practical application of louvre screens (Solomon, 1992), light arrays (Hadderingh et al., 1992; Bruijs et al., 2002), acoustic deterrents (Turnpenny et al., 1998b), bubble screens (Turnpenny, 1998) and the use of turbulent attraction flow (Solomon, 1992). Other behavioural technologies that are used in the USA consist of turbulent attraction flow (Coutant, 2001) and surface collectors (Lemon et al., 2000).

Type of barrier



Louvre screen

Canalized waterways with a uniform approach flow.

Salmonid smolts and adults, adult shad.

Bubble screen

Sites where high performance is not essential. Not fast flowing and/or deep.

Salmonids, cyprinids, shad.

Electric barrier

Not suitable for marine or brackish waters.

Large fish, as relatively low and safe voltages can be used.

Acoustic barrier

High rate flow intakes (< 100% exclusion is acceptable). Need to ensure that sound is constrained so that migration is not unduly influenced

Especially fish with moderate to high hearing sensitivity (e.g. shads, smelt, herring, cyprinids and bass).

Light based systems

Small hydropower intake / pumping stations

Adult eel

Turbulent attraction flow

Small hydropower intake

Smolts of salmonids

Surface collector

Large dams

Smolts of salmonids

Table 5.6: Overview of behavioural barriers for downstream fish migration.


Ad 3. Bypass system The use of mechanical or behavioural barriers can minimise or even avoid entrainment of fish, however an alternative migration route or bypass system is clearly necessary if successful migration is to occur. For fish that migrate near the water surface there are published criteria for the positioning and design of bypasses in small to middle sized rivers. However this is not

the case for larger rivers where further experimental work is required to design a workable solution. For fish that migrate near the bottom, such as eel, several bypass systems are under development. An alternative is to catch and transport fish around the abstraction or hydropower site, especially when more hydropower stations need to be passed, although this is clearly very expensive and often impractical.

Type of bypass



Surface bypass

Bypass situated at the most downstream point of the fish protection system, to which downstream migrating fish are guided (and gather). They are situated in the upper layer of the water column and can be integrated in existing structures, see below.

Salmonids (smolts of salmon and sea trout)

Bottom bypass

Bypass situated at the most downstream point of the fish protection system, to which downstream migrating fish are guided (and gather). They are situated at the bottom of the water column and can be integrated in existing structures, see below.

Eel and bottom orientated species

Bottom gallery

Once eel make contact with a physical barrier they flee upstream via the bottom, instead of searching sideways for an alternative route. Therefore a structure placed at the bottom upstream of the physical barrier could collect eel and guide them to a bypass. In Europe a patented version exists (Bottom galleryR).

Eel and bottom orientated species

Venturi bypass

Bypass system using the venturi principle. A flowing section is created by the main flow (ManshandenTM) from which fish are deflected by light. Very useful for pumping stations. Can be used as surface or bottom bypass.



At hydropower stations that have a weir with an overfall below 10 m in height and a sufficient water depth downstream. Especially suitable at times when the flow over or under the weir is

Weir over falls might be more suitable for salmonids and shad. Weirs that


larger than through the turbines.

are lifted and flow underneath might be more suitable for adult eel and other bottom orientated species, but these can be damaging for smolts.


Locks that function as flow regulators of the turbine, next to the water intake, are possible bypass routes.

Especially in combination with a weir overfall they are suitable for smolts. Underflow structures can be used for eel and bottom orientated species.

Navigation lock

It is possible to use navigation locks for downstream migration, as well as upstream migration. However their location and attraction for downstream migrating fish is often not good.


Fish pass

Fish also use fish passes for downstream migration. Main problem is the attraction of fish passes, with their relatively low flows, for downstream migrating fish as well as the location of the entrance (upstream). It may be possible to connect a surface bypass into the fish pass, in which case the bypass flow would supplement the attraction flow for upstream migrants


Table 5.7: Possible bypasses for downstream migration.

Ad 4. Adjusted or alternative management/ other methods In some cases it is possible to adjust the management of the abstraction in order to prevent or minimise damage to fish. This may consist of seasonal or diel adjustments to the amount of water abstracted, or to the setting of residual flows that must be protected. There are also technical adaptations that might be considered at the design stage such as the type of turbine or pump used, precise design of the spillway,

e.g. water depth etc. and the physical or behavioural screens. Careful management of water approach velocities towards the screen by maximising the surface area of the screen whilst using an appropriate bar spacing is also important., At hydropower stations the use of more turbines to reduce approach flows, the use of turbines that cause least damage (for example with blunt leading vane edges) and adjusted turbine management can all help to reduce fish strike and mortality.


Title Authors Organisation Country

Adaptive management of turbines at hydro-electric dams Niclas Lundh & Arne Johlander Swedish Board of Fisheries, Gothenburg Sweden

through the fish pass, while the main part of the flow goes into the power station. When the water level in the river is high and the power station works at its maximum production, the water level reaches over the steel wall with surplus water going into the fish pass. This makes it easier for fish to find and pass the fish way while there are strong currents in the river.

Introduction Sweden is located in the Northern Europe, bordering the Baltic Sea, Gulf of Bothnia, Kattegat and Skagerrak, between Finland and Norway. Migration solutions (fish ways) have existed here since about 1920-30. The first fish ways in Sweden were probably built about 1870-1890 (they do not however, exist today). Economic interests in salmon fisheries have been a driving force in finding solutions for stock improvement. In Sweden today there are about 500-600 fish ways, most of which are technical solutions. More recently nature like fishways have become more common. In Sweden there is some experience with facilities for downstream migration, one example being the river Mörrumsån in the south of Sweden. Studies started here in 1998 and the project was later started in 2004. National ecological objectives (see www.miljomal.nu/english) and economic interests are the main driving forces for making the fish passage facilities. Atlantic salmon and sea trout are target species, but also other species are included as well.

A monitoring program is to be established, including counting of migrating salmon and sea trout with an automatic counter. The program also includes improvement of salmon and sea trout recruitment in the nursery areas, upstream of the fish ways. To protect the recruitment areas of salmon and sea trout and the river valley, a nature reserve is going to be established along the river.

Photo: Fishway at hemsjö power station in River Mörrumsån in south of Sweden (A. Johlander).

The River Mörrumsån Project The measure here concerns the protection of migrating salmonid smolts. Fish passes were built in 2003/2004 at the Hemsjö power stations in Mörrumsån. During the smolt migration period the power stations reduce operations in order to decrease mortality on passing smolt. The river Mörrumsån Project includes two nature like fishways. A part of the construction is a wall made of steel bars standing parallel to the stream. A minimum flow is always secured



Step 2. Design Passability Once fish have found the entrance, successful passage depends on whether the fish pass provides conditions that are within the swimming capabilities of the fish and therefore is passable. An important factor is the flow pattern within the fish pass. Waterways containing heterogeneous natural flow patterns are easier to pass for migrating fish than technical fish passes where necessarily the total head needs to be gained over a short distance. In technical fish passes maximum drops, velocities, turbulence and water depth need to be carefully established in order to guarantee passability for each of the target species. Important design criteria are: • The drops between pools; • Flow velocities and turbulence; • Water depth and width.

An efficient fish pass is one that allows all fish that wish to pass a structure to do so safely and with minimal delay. The attraction of fish to a pass and the conditions encountered by fish within a pass are both of paramount importance. 5.4.1 Upstream fish migration An efficient fish pass must be both attractive for migrating fish and readily passable by them. To ensure that this is achieved, appropriate guidelines for design, consisting of biological criteria for the target fish species should be taken into account. Knowledge on the local behaviour of target species, including the precise timing of their migration, their responses to flow and the location at an existing structure at which they assemble as they seek to pass it is crucial. Similarly a clear understanding of the swimming and endurance capabilities of each species is required if the pass is to be negotiated with ease and no undue delay. General guidelines for attraction and passability are discussed below. Guidelines for detailed design of a facility are not a part of this guidance, however existing comprehensive technical manuals are identified in the list of references.

For many species, notably cyprinids, it is best to have a diversity of flow velocities and structures along the width and length of the fish pass. These are best provided in a nature-like channel that also offers the opportunity for a pleasing aesthetic appearance. In some circ*mstances the opportunity should be taken to link into agricultural areas next to the facility. Stones or woody structures roughen the bottom and promote the passage of fish and other fauna (invertebrates).

Attractiveness A facility for upstream migration may be confirmed as attractive when it has the ability to effectively attract fish towards the entrance. Attractiveness is clearly at its maximum when it contains the full flow of the river, but when the proportion of the flow that passes through the fish pass or bypass is reduced then the attractiveness will depend on the location of the entrance and the apportionment of flow. It is important to make sure that migration is readily possible at the key times in the year when migration is required.

5.4.2 Downstream fish migration The objective for fish protection at water intakes should be determined first and this should then determine the solution required to protect downstream migrants and define the related design and management criteria. In some cases total protection of fish may be required, for example on some of the Natura 2000 sites. The cumulative impact of multiple abstractions should be considered where relevant. The final design should protect the target species from


entrainment, perhaps by combining a screen with a bypass facility, in order to fulfil the requirements of the river basin plan.

flow in spring time (DVWK, 2002). For downstream migrating Atlantic salmon smolts similar correlations exist (Schwevers, 1999) however these are likely to be river-specific. For adult eel a correlation is suspected with days around the new moon and an increase in river flow in the autumn (Bruijs et al., 2003; Vriese et al., 2006). Since factors other than flow (e.g. water and air temperature, turbidity, flow velocity, oxygen etc.) determine migration activity the reliability of simple generic correlation models is doubtful and therefore it is wise to be cautious when using this approach. Other possible technical warning systems consist of surveillance by under water cameras, or fish detection by sonar. Biological warning systems use the principle that captured fish have the same behaviour as the species in the wild. This is used in the Netherlands and Germany with captured eel that are marked with a transponder, in a MigromatR system (Adam, 2000; Bruijs et al., 2003).

Screens A wide range of physical barriers have been used for fish screening, some of which may also function as behavioural barriers. They can be divided into screening for salmonids and other larger fish and for juvenile and smaller fish (O’ Keefe & Turnpenny, 2005). The most frequently used are mechanical barriers (e.g. trash racks or angled bar racks). Screening efficiency is related to fish length, to bar spacing ratio and to fish response to hydraulic conditions in the front of the barrier and the bypass entrance (Larinier, 2001). Screens should be situated at the point of diversion of water from a river and not within the abstraction channel itself. Bypass systems In addition to screening to prevent fish entrainment into abstraction channels, fish should be provided with an alternative safe route downstream that is readily found. Bypass systems can vary in design and location, depending on the local situation and the target species (e.g. benthic or surface orientated migratory species). A summary and descriptions of the different types is given in table 5.6. The effectiveness of bypass systems depend on the dimensions, shape and precise location of the water off take and the bypass and local hydraulic conditions. One or all of some alternative bypass routes (weirs, navigation locks or fish passes) are generally present at most sites and all can be used effectively by fish in certain circ*mstances.

Fish friendly turbines to reduce passage mortality at hydropower sites have been developed and include blunted leading edges to the turbine blades. Further development depends on improved knowledge of fish passage through the turbines and the factors that influence this including flow velocities. In order to minimise damage of fish when passing turbines, fish friendly turbines should always be taken into account (DVWK, 2003). In circ*mstances where downstream migration protection is not possible programmes to capture fish upstream, transport them via barges or by road and release them downstream of the intake have been adopted. This so-called “Trap and truck” method can be effective where there are multiple intakes in the river, although it is expensive. There is experience with this procedure in the US (pacific salmonid smolts in the Colombia River where there are many large hydropower dams), in Germany (Atlantic smolts in the River Lahn) and in Luxembourg (eel in the River Moselle).

Other solutions for minimising fish damage In many operations it may be more cost effective to reduce or cease abstractions during the migration period of the target species, rather than to install screens. This might be driven by biological criteria such as a US mathematical model that predicts the downstream migration of Pacific salmon smolts based on increasing


Title Author Organisation Country

Flat wedge wire screen for the protection of downstream migrating fish U. Dumont Ingenieurbüro Floecksmühle, Aachen Germany

Results The energy needed for the screen cleaning device and the power supply for the turbines varied between 4,5-11 kWh per day during the measuring period (autumn and winter). This represents 2% of the total energy production (latest results). 4 kW per day was used alone for the power supply for the turbine regulator.

Floecksmühle (www.floecksmuehle.com) has equipped its own hydro-electric power station (flow discharge of ca. 2m3/s) with a fish screen with 5 mm spacing, in a project promoted by the Deutsche Umweltstiftung. Studies have shown that downstream migrating salmon smolt and silver eel were not damaged by this type of construction and that the bypass enabled the safe migration of fish. Experience gathered during the operation of the facilities show that the chosen arrangement of the surface, the angle of the rash track and the approach velocity enable operation of the plant even in cases of high concentrations of trash and gravel at the screen (Dumont et al., 2005). An efficient screen cleaner has been installed to cope with cleaning during the periods of higher concentration. After three years experience it can be concluded that: • The operation of the hydropower installation is, from a technical and economic perspective, possible when using a 5,3mm wedge wire screen; • The chosen hydraulic conditions (spacing, screen surface and approach velocity) permit maintenance of the screen.

The head loss due to the screen when cleaned and in operation during the measuring period, reduced the overall utilised head drop for generation. These reductions and thus the reduced energy production, must be seen in relation to comparable losses through the use of a conventional 20 mm screen which are approximately 1% to 2%. Conclusions • From a technical point of view fish screens with a spacing of 5 to 10 mm. can be used for installations up to appr. 20 m3/s. (per unit) at present; • There is no screening problem (design of screens according to needs of fish are well known) but a cleaning problem for mid size and large installations.

Photo: Fish Screen in Ochtenburg during the installation.

Dimensions Width: Length: Flow discharge: Spacing: Material:


2,35 m 3,30 m 1,7 m3/s 5 mm Stainless steel

Title Author Organisation Country

The development and evaluation of downstream bypasses for juvenile salmonids at small hydro-electric plants M. Larinier Conseil Supérieur de la Pêche-Cemagref, Toulouse France

and insufficient discharge were identified through direct and video observations as being responsible for many aborted passages at the bypass entrances. The results suggest that siting of surface bypass systems must take into account flow patterns in both the trash rack area and intake channel. It is suggested that surface bypasses associated with existing trash racks may be an acceptable mitigation technology at small-scale hydro-electric projects where it is not necessary to guarantee a highly efficient downstream passage protection.

Introduction Numerous experiments have been conducted from 1992 to 2001 to quantify the efficiency of surface bypasses associated with conventional trash racks for diverting juvenile salmon from turbine intakes (Larinier et al., 1994; Larinier et al., 2002; Travade & Larinier, 2006). They were conducted at eleven small-scale hydro-electric plants on salmon rivers in the Southwest of France (Gave de Pau, Gave d’Aspe, Gave d’Ossau, Nive, Garonne, Ariège) to relate downstream bypass efficiency to hydraulic conditions and to the behaviour of salmon (Salmo salar) and sea trout (Salmo trutta) smolts in the intake channel. The maximum turbine discharge varied from 20 m3/s to 90 m3/s and the width of intakes varied from 11 m to 30 m depending on the plant. The surface bypasses were generally located laterally along the intake at one end of the trash rack. The mean bypass discharges varied from 0.4 m3/s to 4 m3/s, or an average of 1.5% to 8% of the turbine discharge.

Photo: Surface fish bypass at Haslou power plant intake.

Results The efficiency of the surface bypasses was evaluated by a mark-recapture technique. Radio telemetry was used to monitor movement patterns of salmon and sea trout smolts in front of the intake and near bypass entrances. Depending on the site, the mean bypass efficiency was found to be between 17% and more than 90%.

Photo: Hydro-electric power dams cause a serious problem for fish migration.

A bar spacing of about 1/7 to 1/8 of the fish length seems to ensure a marked avoidance response. Behaviour of fish in the vicinity of the trash rack and the bypass is largely influenced by the flow pattern. Poor hydraulic conditions (turbulence, strong acceleration, upwellings)


Title Author Organisation Country

Saving downstream migrating fish in the Netherlands: ‘Manshanden fishway’ for pumping stations M. Klinge Witteveen + Bos Consultancy, Deventer The Netherlands

Introduction Diadromous fish produced within the Dutch polders, or equivalent low land areas, encounter at least one pumping station during their downstream migration. In total there are more than 3000 pumping stations for drainage of polders in the Netherlands alone. These pumping stations present migration barriers for fish by blocking the entire width of the streambed at the connection between adjacent water bodies and consequently the only potential route for passage past the pumping station is through the pumps. The pumps are usually propelleror centrifugal pumps that rotate at high speed and represent a very high risk of severe or even lethal damage to fish. The risk is greatest for fish over 10 centimetres in length representing adult specimens of most species and all eels. For these fish the chances of surviving passage through pumping stations are often small. Until recently no suitable solutions existed to facilitate downstream migration of fish past the pumping stations and this led to the professional fisherman and inventor Gerard Manshanden and Witteveen+Bos Consulting Engineers to develop the Manshanden fish-way for pumping stations. This facility keeps fish from entering the pumps and provides alternative routes to bypass the lethal pumps.

The core of the Manshanden fish way is a Venturi pump, which is installed at a pumping station in addition to conventional pumps. The Venturi pump creates a water flow and forces the water through a narrow opening into a discharge pipe in which a vacuum develops as a result. The vacuum induces a water flow in two side channels that are connected to the discharge pipe behind the pump. The two side channels stretch back past the inlet of the pumping station to the lower level waters of the polder. The bypasses provide an obstacle-free connection between the upstream and downstream waters. Fish that approach the pumping station from the polder are discouraged from swimming into the inlet pipe of the station by strong stroboscopic lights. Since fish have an aversion to strong light, they will not enter the illuminated inlet of the pumping station and instead search for alternative water streams nearby. The dark and quiet inlets of the bypasses attract the fish which are guided by the water flow in the bypasses until they reach the waters downstream from the pumping station where they can continue their downstream migration undamaged. Results The first Manshanden fish way was installed on the Oude Aa pumping station in the River Oude Aa, part of the conservancy area of the Hunze and Aa’s Water Board and has been in operation since October 2005. During the first week of its operation, which coincided with the last days of the autumn migration of fish, more than 5000 fish passed through the new facility, each of them reaching the downstream waters fit and completely unharmed. In contrast, all fish above 10 centimetres in length that passed

Photo: Fish damaged by a pumping station.


through the conventional pumps when the stroboscopic lights were not operational were killed. This shows that the Manshanden fish way for pumping stations is a very effective measure to save large numbers of fish. When one considers that more than 5000 fish were saved during a single week at the Oude Aa

pumping station, even conservative calculations indicate that several million fish are killed by pumping stations in the Netherlands alone every year. Hence, the application of migration facilities, such as the Manshanden fish way for pumping stations, could be an important contribution to healthier fish stocks.

Map: Schematic overview of the Manshanden fish way.



Step 3. Construction and maintenance

5.5.1 Construction Upstream facilities Every design should be very carefully checked on biological and hydraulic criteria prior to construction: • Is the entrance of the fish pass easy to locate? • Will it contain enough water to attract fish at the critical times of the year? • Is the entrance located as close as possible to the toe of the weir? • Is the turbulence in the pass within acceptable limits? • Will the fish pass be passable for each of the target species? • Is the fish pass large enough to accommodate peak migrations of the target species? • Are there sufficient arrangements to exclude debris? • Can the fish pass be negotiated by swimming (instead of jumping) • Is the diversity of stream flows in the fish pass maximised? • Note that an ecological, or “nature-like” design is often preferred above a technical design, particularly for smaller fish with low swimming capabilities. • Does the fish pass provide a route for fish migration throughout the whole year? • Is the fish exit from the fish pass sufficiently far away from the weir, dam etc. in order to prevent migrating fish from being swept downstream? • Can the fish pass be easily accessed for clearing of debris and maintenance?

stream facility should also be carefully checked prior to construction: • Every opportunity has been taken to reduce entrainment risk by setting an appropriate abstraction management regime; • The facility functions during the critical migration period of each target fish species and each relevant life stage; • Flow velocities in front of the physical barriers are below the escape velocities of the target species and life stages; • Screens should be designed with at least 20% over capacity to allow for partial blockage or blinding (O’Keefe & Turnpenny, 2005); • Flow conditions in front of physical barriers are uniform, high velocity hot spots don’t occur; • The selected mesh aperture or behavioural guidance method excludes, protects or guides the target fish to a bypass (for onwards migration); • The amount of flow is sufficient to attract fish to the bypass; • The entrance of the bypass is located at the point to which the fish are guided; • The bypass entrance provides good hydraulic conditions that deter fish from escape once entered; • The bypass is open topped and presents no visible deterrence for fish; • The outfall of the bypass is out of reach of the turbulent zone and the fall is not higher than 10 m; • Downstream the water depth is sufficient and the risk for predation by birds or fish for the returned fish is minimal.

And finally, • Is the facility safe for all who visit it?

Tip: 1. Use a checklist to ensure that all new fish migration facilities are appropriately designed, efficient and safe.

Downstream facilities Similarly, the proposed design of a down-


5.5.2 Operational and structural maintenance Maintenance is often neglected, unless a system is formalized in writing and owners/ operators tend to assume that fish pass facilities function throughout the year. In many cases this neglect often leads to clogging by branches, leaves, algae, debris etc. resulting in partial or total blockage of the fish pass. Consequently the flow through the fish pass can be severely reduced, with adverse implication on fish attraction and passage.

In order to make sure that facilities function as they are designed, a clear maintenance plan should be prepared and carried out. In the UK it is a legal duty for fish passes for migratory salmonids to be maintained in an efficient state and it is an offence not to do so. Maintenance is best done as part of a structured inspection programme or protocol that defines the times when the facility must work. For example in Finland fish passes are closed during the winter, or the amount of water is significantly reduced to prevent ice formation. Maintenance needs to be carried in the period prior to the migration period of the target species. The intensity of maintenance may differ per site, depending on local circ*mstances and this will be readily identified following operational experience and an objective risk assessment (Armstrong et al., 2005). In addition to structural maintenance, regular inspection is necessary to avoid malfunctioning due to blockage.

Facilities for downstream migration, such as physical screens, are only efficient if they are correctly operated, cleaned and maintained. They should be located so that regular cleaning and maintenance is easy and safe to carry out. Common problems with mesh panel and bar screens include structural damage, damaged screen seals, screens not fully seated, screens removed to avoid clogging problems and screens heavily clogged (Turnpenny et al., 1998a; Turnpenny et al., 2005).

Maintenance of fish passes and screening facilities is inherently dangerous and it is essential for the operator that health and safety issues are taken into account.

Target species A Allis shad (Alosa alosa), B Houting (Core-

Tips: 1. Define the required period of operation of the facility. 2. Create protocols for maintenance of fish pass facilities. 3. Maintenance officers need biological and hydrological instructions for optimal maintenance. 4. Take health and safety very seriously.

gonus (lavaretus) oxyrhynchus) and C Eel (Anguilla anguilla).





Title Author Organisation Country

Maintenance and operating protocols P.P. Schollema & H. Wanningen Hunze and Aa’s Water Board The Netherlands

For migratory fish it is very important that a fish pass, natural or technical, functions effectively when needed, during the key migration periods. To ensure this a fish pass needs regular inspection and maintenance. The Hunze and Aa’s Water Board experienced problems for some of their fish passes in small rivers and canals. In some cases the facilities were not functioning and migratory fish could not use the fish pass due to the absence of simple structural maintenance and operating instructions.

and other interested persons about the fish passes. The protocols are also published on the website of the water board, so members of the public can look up information about the fish passes. For an overview of fishpasses in The Netherlands see www.vismigratie.nl and www.hunzeenaas.nl (only Hunze en Aa’s Water Board management area).

Photo: Example of a not functioning bypass system due to poor maintenance.

From 2004 the Hunze and Aa’s Water Board developed maintenance protocols. A practical student, an ecologist, a hydrologist and a maintenance officer worked together to produce a standardised protocol containing: • A map showing the location of the fish pass; • Photos of the fish pass to give an impression of the dimensions; • Information about the type of fish pass, construction data and the way in which it operates; • The maintenance and operation protocols themselves. Depending on the type of fish pass, the key maintenance and operation requirements are described here; • A table with the tasks for maintenance and operation of the fish pass and identity of the responsible person; • Points of interest concerning the presence of special fish species or planned monitoring projects; • List with relevant literature. The protocol is implemented in the policy of the water board and for every new fish pass a new protocol will be written. It is necessary to regularly check if the protocols are still up-todate and relevant. The protocols have proved to be a useful means to inform new employees



6. Monitoring and evaluation Many fish passes are constructed all over Europe, but monitoring of their performance is extremely limited or sometimes virtually non-existent. This is because of the high cost for effective monitoring and the low perceived benefit. Nevertheless, fish passes themselves can be very expensive and it is essential that their effectiveness is demonstrated so that they may be optimised. Any improvement to fish passage at an existing obstruction is beneficial. It is also important to learn how well fish passes function so that we may confirm that management systems are optimal and so that we may progressively improve our designs.


be very high, it cannot necessarily be taken as an indication of good performance of the fish pass.

Monitoring of fish passes is vital to evaluate the hydraulic functioning of the pass, to evaluate the efficiency with which fish use the pass and in some cases also to evaluate the consequences of the pass on a fish population or fish stock. In general monitoring contributes to a learning process to improve future designs and to detect shortcomings of facilities.

The efficiency depends on the general criteria that are set in the previous chapter. The efficiency of a fish pass refers to the proportion of a fish stock present at the obstruction, that enters and successfully moves through the facility without undue delay (Larinier, 2001). Cumulative effects should be considered when several obstacles occur in a river.

This chapter sets out the relevant questions that should be considered as part of an evaluation programme, the practical aspects of addressing these and considers who might carry this out. Monitoring should always be part of an evaluation programme.

Evaluation should assess quantitative goals set for effectiveness for each target species, set as the percentage of the population that should pass and the acceptable migration delay. For anadromous species like salmon, passage of the whole population is usually required and delay minimised when the obstacle is downstream of spawning grounds. If significant spawning grounds are located below the obstacle, then performance goals can be less stringent. This is also the case for potamodromous species, where effectiveness is also judged by the number or proportion of the stock that safely passes.

6.1 EVALUATION OF THE FISH PASS The key questions are focused on the effectiveness, efficiency and hydraulic functioning of the fish pass. They differ for upstream and downstream facilities. 6.1.1 Upstream migration Monitoring of a fish pass is of great importance to evaluate the effectiveness and efficiency with which it works. The effectiveness of a pass is a qualitative description of the performance. For upstream migration effectiveness depends on attractiveness, passability and the ecological characteristics of the fish pass. General questions are: • What species use the facility? • Do all target species (in all life stages) use the facility? • What fractions (of the migrating populations) pass the facility? • Does the facility have a habitat function for target species? • What influence does the facility have on the fish stock?

6.1.2 Downstream migration Monitoring of the performance of facilities for downstream migration usually focus on the estimation of mortality and damage to downstream migrating fish by turbines and entrainment of fish into water intakes and the efficiency of the facilities for fish protection and guidance. Damage or mortality rates can differ a lot, depending on several factors (e.g. fish species and length, intake approach velocity, turbine type) and therefore the first step is to determine whether a facility for downstream migration is necessary. Questions that need to be answered are: • What is the potential presence of downstream migrating fish? • What is the percentage of damage and mortality at the site?

Note: The effectiveness demonstrates that some fish are able to use the pass and, even though numbers of fish recorded using the facility may


Title Author Organisation


Re-establishing connectivity in the Danube basin A. Zitek1, M. Jungwirth1, T. Bauer2, T. Kaufmann2 & S. Schmutz1 1 University of Natural Resources and Applied Life Sciences, BOKU, Vienna. 2 “Freiwasser” - Working Group for Ecology, Hydraulic Engineering and Water Management Austria

Introduction Within the LIFE-Nature project “Living space of Danube salmon” between 1999-2003, the efficiency of different restoration measures to improve habitat conditions for Hucho hucho (L.), one of the most endangered fish species of Europe, was monitored. The monitoring included investigation of fish migration at 9 out of 11 newly constructed fish ladders and evaluation of the development of fish populations within the whole study area. Successful migration processes were documented within the whole study area, varying between 8 and 33 species and 38 and 2098 individuals passing the fish migration facilities. In total 10 individuals of the “Danube salmon”, Hucho hucho (L.), were caught at fish ladders, but the most frequent species in traps was Barbus barbus (L.). Some individuals of Barbus barbus (L.), but also of small-sized species like Alburnus alburnus (L.) and Gobio gobio (L.), belonging to the Danube population, were found to migrate more than 9 km into the tributaries passing three fish-ladders during one season. Marked individuals of Barbus barbus (L.) from different river sections were found to use the same winter habitats in tributaries, documenting the re-connection of formerly fragmented populations. The re-open-

ing of the river continuum resulted in a re-increase of river type specific species within the whole tributary system, for some of them successful reproduction has been re-established in areas where they formerly naturally occurred. Methods Traps & different marking methods (Zitek & Schmutz, 2004; Zitek et al., 2004). The evaluation of the functionality of the fish ladders was based on the “National guideline for a minimum monitoring program for fish ladders” (Woschitz et al., 2003). Technical information nature like rock ramp in the river Melk Date of completion: 10.10.2002 Type of fish ladder: nature like rock ramp Length: 89 m, varying with water level of the Danube Bypassed height/slope: 3,4m/3,8% Discharge: 500 l/s - 1200 l/s; total NQ Monitoring data Monitoring time frame: 07.03.-26.06.03 Total number of species: 33 FFH-species: 4 Functionality: excellent

Photos: Situation prior and after construction of the fish ladder at the confluence of the river Melk with the Danube (Copyright “Freiwasser”).


In some cases downstream migration can continue without specific facilities through slight adaptations to abstraction management or turbine operation in order to improve downstream migration conditions. Ideally all of the possible migration routes e.g. turbine, spill way, sluices and any fish pass should be monitored at the same time, however this is often impractical or expensive.

dependent methods that give information on the timing of use of the pass, the species that use it and their sizes. Other fishery surveys, including electro fishing or trapping upstream and even rod catches and spawning observations can be used for direct or indirect estimation of effectiveness. Capture independent methods such as simple visual inspections, and fish counters within the pass including video techniques, can be applied for effectiveness of a fish pass. Fish counters can provide very good quantitative data on the numbers of fish ascending and descending a fish pass. All require to be operated in relatively non-turbulent water, which is generally found at the exit of the fish pass, but may also be found in the laminar flows of orifices or slots. Different types of counters exist, which can offer differing characteristics of accuracy, species identification, manpower costs, the size of the pass and the volume of water where they can be used and also individual fish measurement (Armstrong et al., 2005). Some are available “off the shelf”, for example the icelandic Vaki system, whereas others use cheaper modular deployments of underwater cameras and lighting systems (J. Gregory, pers. Comm.).

The evaluation should include: • What is the entrainment rate into the water intake or turbine? • What is the damage rate and mortality rate of fish (%) caused by turbines or other parts of the plant? • What is the preferred safe migration route and can it be improved? • What is the efficiency of the downstream migration facility, based on attractiveness and safe passage of fish through the facility? 6.2 CHOICE OF MONITORING METHODS Methods for monitoring upstream and downstream migration can be divided into capturedependent and capture-independent methods. Capture dependent techniques consist of the capture or recapture of fish, some of which may be marked as part of a mark and recapture experimental design. Capture independent techniques consist of visual observations such as video monitoring, automatic (resistance) counters, sonar-techniques and other telemetric techniques such as radio or acoustic tracking systems. It is very important to clearly identify the objectives of the monitoring programme, so that resources are used in the most effective way.

Efficiency The efficiency of a fish pass is usually defined as the proportion of available fish that successfully use the pass. In its simplest form efficiency (E) is that proportion of the available stock of fish (N) which succeed in ascending or descending a fish pass (n). E = n/N

6.2.1 Upstream fish migration Effectiveness The effectiveness of a fish pass is a qualitative judgement on performance and can be determined either directly or indirectly. Capture techniques, for example trapping within or immediately upstream of the fish pass are capture

An efficient fish pass is additionally one that passes a high proportion of the fish without undue delay (Armstrong et al., 2005). Determining the efficiency of a pass is more intensive and expensive than simply determining the effectiveness of a fish pass, and sites are usually selected


on a strategic basis for long-term assessments and in the lower reach of the main river. In some cases temporary counting facilities may be required to demonstrate that fish passes are functioning over the required range of flows.

careful placed receivers can reveal when fish approach a fish pass, the locations where fish search for an entrance, or how fish use natural bypass channels as a new habitat. This knowledge can be used in many ways, for example to adapt management of the fish pass and for improvement of the design of natural bypass channels. Passive Integrated Transponders (PIT-tags) have been developed as small tags for fisheries studies. These emit a signal when interrogated, for example when the tagged fish pass a cable on the water bottom, a scanner at a fish pass entrance or exit, or come within range of a handheld antenna (Vaate & Breukelaar, 2001).

A count of the fish passing through a fish pass is not in itself a measure of efficiency. For that the number of fish available to migrate through the pass is also required, and that may come from an estimate of abundance from a fish counter downstream (Larinier & Travade, 1992). Various trapping and tagging programmes may also be helpful. Tagging studies might use simple colour batch marks or tags applied in trapping programmes downstream that may subsequently be identified in trapping studies upstream. Recapture of fish is best achieved using a simple fish trap within the fish pass or for some species by using fyke nets upstream of the fish pass. It is then possible to determine the efficiency of the fish pass by relating the amount of marked fish recaptured within the total catch.

Sonar techniques are a capture-independent technique that can detect fish in three dimensions (split beam) and determine the swimming direction and depth of fish (Kemper, 2005). However they cannot usually be used in depths less than 2 m. and are very sensitive to entrained air, which is of course common at many fish passes, and they cannot identify fish species. Overall the preferred method is telemetry because of the amount and quality of data it yields, however it is recognised that this is relatively expensive.

At the other end of the scale are the more complex PIT tagging or radio telemetric tracking programmes from which far more valuable information on fish behaviour in the vicinity of the pass and passage itself can be derived.

Recapture of tagged fish is of course possible at more than one location upstream, and radiotagged fish can be tracked for many months, both yielding information on the performance of more than one pass in a river.

Commercially available miniature radio tags can be implanted in fish or placed in the stomachs of larger salmon. They transmit a signal either continuously or at specified intervals and Photo:






Hydraulic measurements Measurement of the hydraulic conditions in the pass should occur under a variety of flows. This is to ensure that the pass meets the original design criteria and thus is suitable for the particular target species. It also ensures that the facility operates effectively across the expected range of river discharge and levels (Armstrong et al., 2005) and can help to optimise fish pass operation.




Title Author Organisation Country

Monitoring of fish migration behaviour in large artificial lakes D. Veselý Povodí Moravy, s.p., Brno Czech Republic

Introduction The cascade of the three Nové Mlýny reservoirs forms a full obstruction to fish migration in the River Dyje. The obstacle is not only the three reservoir dams but also the still water of the three artificial lakes. This is why the Moravian Fishermen´s Union, in cooperation with the Institute for Biology of Vertebrates of the Academy of Science of the Czech Republic and the Institute of Fishing and Hydro-Biology of the Mendel University of Agriculture and Forestry, launched a project in the lower reservoir Nové

Mlýny. The project started in 2001 and by 2005, 36,000 carps were marked and released. Marking All marked carp caught by anglers have been recorded and the data have been used to assess migration routes between the lakes and their tributaries. Understanding the migration patterns will by very useful in considering fish passes over the reservoir dams and the improvement of migration conditions within the artificial lakes.

Photo: Reservoir Nové Mlýny (Copyright M. Cizmarik).


Results from hydraulic measurements can serve as contractual approval when a fish pass is completed by the constructers. It is recommended that the results of measurement programmes are retained as part of the overall evaluation program (local hydrological conditions, the hydraulic conditions within the pass as well as the target species and size of fish and the location of the fish pass.

The rate of mortality or damage should be calculated for each of the target species, and the management of the plant needs to be related to the results. Capture methods for these assessments usually consist of capture dependent methods such as large nets, however these are strongly influenced by the discharge of the river. Fish, both alive and dead can be captured from any fish return system associated with the abstraction, and dead or damaged fish can also be found in the trash that is collected from the trash rack. Both can be checked on a routine basis, and both can be managed to provide quantitative monitoring data.

6.2.2 Downstream fish migration It is equally important to understand the impact of abstractions and non-consumptive hydropower schemes on downstream migration of fish, and the performance of facilities to prevent or minimise damage. Different methods are used to monitor the performance of facilities for downstream migration and for protection.

Preferred migration route Where there is more than one potential route for fish it may be important to know which is preferred so that it may be managed appropriately. Tagging studies of various kinds can provide this information for example trapping within each route, which may include mark and recapture methods can provide evidence of fish passage and the relative importance of each route. Fish can be dyed with colour marks, tagged with plastic marks or with fluorescent float tags or self inflating turb-tags and marked fish can be recaptured using fyke nets or some other nets or traps downstream. A grid trap such as a Wolf trap at the end of a bypass system allows water to pass through, while fish are flushed along the slats and into a holding tank downstream. With this system the effectiveness of a bypass can be determined as well as the recapture of marked fish. In some circ*mstances automatic fish counters can also be used to measure entrainment and also the effectiveness of bypasses, however this is a relatively expensive technique and application may be limited.

Damage rate and mortality rate The loss through entrainment into abstractions and the damage and mortality of fish at other facilities should be determined for each target species, in terms of numbers and biomass. Damage at the facility and protection by screens can differ considerably between species. Monitoring should distinguish between fish that are dead or lethally damaged, those with sub lethal damage and those fish with no damage. It may be necessary to retain fish from the monitoring programme for a short period of time (1 or 2 days) to assess delayed mortality. The mortality rate is the proportion of the total number of fish (n) that are dead (d). M = d / n * 100 The damage rate includes the damaged fish (v): M = d + v / n * 100 In case of multiple sites (i) in the river system that cause damage, the total damage rate (Stot) can be calculated by:

Efficiency of the facility, based on attractiveness and passage of fish through the facility Capture of fish downstream of the abstraction point or the bypass by various trapping methods

Stot = ∑ (di + vi ) / ∑ ni * 100


Title Author Organisation Country

Fish passes and water flow G. Rasmussen Danish Institute for Fisheries Research (DIFRES), Silkeborg Denmark

Monitoring methods In the period 2003-05 a total of 23,400 trout smolts and 7,400 salmon smolts were tagged (adipose fin clip and panjet marking) and released above and below 20 fish farms obstacles and 3 small water power stations in three different river systems. A smolt trap running below the lower obstacles in each river system enabled calculation of smolt loss and the time delay of migration. A couple of years ago the River Skjern in west Jutland had its lower course (20 km) before the outlet into the sea restored and a new shallow lake was established in an affluent just before the outlet in the River Skjern. Smolts traps (whirling traps), tagging smolts with radio tags and estimates of the pike population in the new lake combined with stomach examination enabled estimates on smolt loss of salmon and trout to be made (Aarestrup & Koed, 2003; Aarestrup, et al., 2003).

Introduction The main problem (excluding habitat degradation) in Danish watercourses are obstacles in connection with freshwater (rainbow trout) fish farms (about 350), small water power stations (about 75), and old water mill obstacles (several hundreds) (Svendsen et al., 2004). The freshwater farms are situated in Jutland which is where we have most and better water and the salmon (at present 8 rivers) and most of the trout (several hundreds) rivers. The effect of these operations is the loss of migrating smolts of salmon and trout into water intakes to the fish farms; delay of the smolt migration and predation from pike in the impounded zone upstream of the weirs. This is in addition to problems with upstream migration of mature salmonid and other fish species. Dams associated with the hydropower stations and the water mills create artificial lakes within which the smolts are delayed and suffer predation by pike, pikeperch and birds and mostly damaged and after which many are killed when passing the turbines.

Results The smolt loss from the fish farms study when passing an obstacle varied from 0 % to 83 % with a mean for salmon and trout of 45 %, and the time delay varied from 0 to 17 days with a mean for salmon and trout of 5.3 days. The smolt loss is positively related to the fraction of water abstracted to the fish farm compared to total water flow; and the smolt loss is a combination of predation and de-smoltification because of the time delay. The problems for the salmonid stocks with several consecutive fish farm obstacles are evident. The smolt loss when passing power stations varied from 94 % to 100 %. The smolt loss in River Skjern was about 20 % but in the new lake about 75 % of the smolts were predated by the new established pike population and birds, mostly cormorants.

A similar problem is the establishment of wetland lakes; either rehabilitation of old drained lakes or new lakes in the watercourse in order to reduce (i.e. de-nitrification) the amount of nitrogen from the water before outlet to the sea. The downstream migrating smolts of salmon and trout are again delayed and predated on by pike and birds. Basically the problems with new wetland lakes are similar to those with artificial dams and lakes above obstacles (Aarestrup, et al., 1999; Koed et al., 2002).


Tips: 1. Monitor the hydraulic performance of the facility immediately after construction. The results can represent approval and acceptance of the construction as conforming with contractual requirements. 2. Identify fish passes situated on strategic locations in the river basin for the monitoring of both the performance of the structure and the overall effect on fish populations (a quantitative approach). A scientific approach to monitoring is usually required and appropriate advice on this should be sought. 3. Include plans for evaluation of the facility at an early stage, so that necessary facilities are included within the design process. 4. The objective of the evaluation is to quantify the effectiveness of the facility, but this should also answer whether the facility contributes to reaching good ecological status respective the WFD. 5. Evaluation can also help us to improve our design criteria and information should therefore be widely shared. 6. All downstream facilities should be evaluated on a scientific basis. The number of facilities is still relatively small and we need to improve our understanding of the principles of downstream migration protection and the response of different fish species to systems for protection and bypassing, adapted management, and for fish friendly solutions.

(Canadian rotary screw traps are increasingly being used) or by electrofishing can provide an estimate the numbers of fish that pass the inlet screen (Turnpenny & O´Keefe, 2005). Once again the best results are obtained when using radio or acoustic tagging (telemetry) or passive integrated transponders (PIT tags) or in some cases hydroacoustic methods. 6.3 ASPECTS OF EVALUATION IN PRACTICE Once the information requirements related to migration at obstacles and to fish protection at abstractions have been clearly identified then an evaluation program can be designed. Important factors to consider include costs in terms of the people who will be involved, time schedules and the required period of monitoring, etc. A programme should aim to deliver the requisite information for each target species and may need, therefore, to operate only in specified months of the year. In Finland for example the fish migration period starts usually in April May in the southern areas and in the northern areas in June and ceases as water temperatures drop in October. Fish passes and bypasses can of course provide a good opportunity for monitoring fish stocks in a river in addition to the requirement to monitor performance of the structure itself. It is important that the chosen method does not affect the migrating fish. Programmes such as these are generally required by the national organisation charged with protecting fisheries and it may be the responsibility in law of the owner or operator of the structures that necessitated the fish pass in the first place to carry out monitoring. New projects to fit fish passes to old weirs and dams should have appropriate monitoring built in. In some countries it may be necessary to obtain appropriate legal permissions and exemptions for monitoring, for example when handling protected fish for research purposes or using equipment such as radio transmitting tags that are regulated by national legislation.


Title Author Organisation Country

Overview of fish pass facilities in Portugal Jorge Bochechas & Marta Santo Direcção Geral dos Recursos Florestais, Lisboa Portugal

as it is considered that the passes would not contribute significantly to mitigation of impact. It was only in 1951 that the first known fish pass, a pool and weir pass, was built in Portugal. However legislation dating back to 1893 refers to the need for the implementation of fish ways in dams and other barriers in inland waters. Fish ways in Portugal are installed mainly in small hydroelectric dams/weirs in the Northern part of Portugal (north of Tagus River), there being only one in the south. Most of fish passes constructed in Portugal during the last 15 years are in new dams or weirs (Santo, 2005) and the budget for them is included in the global project budget. The national legislation on inland fisheries requires the application of measures for mitigation of the impacts of dams and weirs, and this includes the installation of fish passes.

Fish passes in Portugal are classified (based on direct observation and some measurements) on a scale from 1 to 5 where 1 corresponds to the less favourable situation and 5 to the more favourable one. 11 of the total existing fish

Map: Distribution of fish ways in Portugal (main river basins).

The main problem is that although legislation requires the installation of fish passes, it does not mention that they have to be efficient for fish migration. So we have many fish passes that are not useful due to lack of maintenance or bad construction. We have some monitoring programmes for passes but they are not permanent, in general lasting for one or two years only. This is mainly due to a lack of budget and personnel. We have used video techniques in Borland fish locks and in one fish lift. We also use this technique in a nature like fish pass and in a model in the laboratory. Other techniques commonly used in pool and weir fish passes are infrared sensors (the River watcher made by Vaki, Iceland) and telemetry with radio fish-tags. In Southern Portugal the more frequent transversal fluvial constructions are related to irrigation and urban water supply. It is not common for fish pass installations in these constructions


Attraction problems or the impossibility of fish getting to the fish pass entrance.

passes (42) are not working, and information is not available for 3 of them. At least 15 them are considered ineffective for upstream migration (information is not available for 3 of them) and the main causes are: • The fish pass is not working; • Design problems; • Maintenance problems;

Photo: Shape detail of Nunes fish way.

Photo: Vertical slot fish way (Penacova).

The more frequent target species are Chondrostoma sp., Barbus sp. and Salmo trutta fario. Some fish passes (mainly the ones built in large rivers) are also for Petromyzon marinus, Alosa alosa, Alosa fallax and Anguilla anguilla.

Photo: Fish way with deep side notches and submerged Photo: Pool fish pass with notches only (Ponte de Lima).

orifices (Avô).



7. Communication and education “Fish are a helpful focus upon which community involvement in environmental projects can be developed. When involving the community in an environmental education project you often gain important local insight from fishermen who often have very good knowledge of the status of rivers, whilst having their own firmly held views on what should be done! They are aware of the impact of dams and weirs on fish migration and the importance of water quality and quantity for fish survival. Achieving fish migration is an ultimate goal of the work being undertaken. However we believe that environmental education and the involvement of society in our projects is an essential part of the process to achieve this goal.”


7.1 EXCHANGE OF INFORMATION The establishment of an independent national panel of experts on fish migration matters has provided an effective channel for the exchange of information and expertise. These panels act as centres for expertise on all issues relating to fish migration and facilities. These include advice on design criteria and standards, new developments in these areas, the existence and implementation of appropriate local and European regulations and perhaps most importantly the provision of assistance to managers and local bodies. Some panels might also be able to help and advise on the availability of grants and other funding sources for pass construction projects, project management, the subsidization of research and development and also the maintenance of an area or national database.

der fish migration issues. Other examples of structural international communication between expert groups relates to countries that share a river basin, for example the International Association for Danube research (AID), the International Commission of Protection of the Rhine (IRC) and Meuse (ICBM). Communication between the countries in mainland Europe is gaining in importance since implementation of the Water Framework Directive. In addition to the existing expert networks, international symposia provide a platform and opportunity to exchange information on general or specific technical topics such as the restoration of river basins. Relevant recent international symposia have been held in 1990 in Japan (Komura, 1990), in 1996 in Austria (Jungwirth et al., 1998) and 2006 in Austria (FAO, 2006).

At the European level the expert group on fish migration matters is the European Inland Fisheries Advisory Committee of the FAO (EIFAC) which meets on a regular basis to discuss cross bor-

The exchange of information, e.g. research reports, project records and scientific publications is very important if we are to gain from the experience of others. The networks referred to above facilitate direct communication between regional authorities and non governmental organisations and there is no reason why international networks cannot also be used to mutual advantage. Nowadays the internet is an important medium for sharing information. Appendix II lists relevant internet sites in Europe with respect to fish migration topics and expert networks. Interactive information systems, e.g. interactive mapping based on GIS are also promising tools for information exchange. An example is ESIS: a prospective ‘European Salmonid Information System’ (Dijkers & bij de Vaate, 2002). Additionally, there are some national internet orientated databases such as the internet orientated databases (GIS) in Flanders, Belgium (www.vismigratie.be). Further databases are being developed in Finland and in the Netherlands (www.vismigratie.nl).

Photo: Exchanging information about education projects on a Community Rivers Project fieldtrip.


Title Author Organisation Country

Community involvement along the river Llobregat, Catalonia R. Casas Llobregat Fluvial Park, Berga Catalonia (Spain)

The Fluvial Park pilot project is taking place in Viladomiu Vell, one of the 16 colonies in the Park where there is a well-organized Neighbourhood Association and Fisherman’s Society. The project sets an itinerary with education boards relating to seven different topics (colony, allotments, bridge, river, fishing, forest and dam). Each of the boards provides information about the link between the natural environment with the actual colony. What is special about the boards is that they have been prepared with the involvement of the community and the local people and fishermen of the colony who have provided information and personal views about each of the 7 elements. Also 9 different schools from the area have participated with a drawing competition and some advice.

the 7 boards as a representation of the schools who participated in the project. The final drawings were voted upon by the neighbours of Viladomiu Vell. Community involvement in any kind of project is not always easy in terms of coordinating people and securing agreement, but if it works it is a good way to secure a successful project. It ensures more input and support. At the end of the day, not everyone will participate (we have to be realistic) but it identifies those who are really interested and who will be there for future partnership work.

The involvement of the community was mostly achieved by meetings in the colony and informal meetings with the people, getting to know their views and posing questions about each element. Some formal meetings were held to give information about the future itinerary and to ask for feedback. As a result, each of the 7 boards reflects the views of the people through a dialogue between three characters (grandmother, father and grandson), providing some technical information and one activity. The involvement of the schools was through a drawing competition. First of all, there was a visit to each of the schools to explain the project and to invite their participation. Each of the schools involved chose one of the 7 topics to draw. Some meetings were with one representative of each school to give advice and guidance on how to focus the drawing competition and how an educational program should be run on the future. Eventually only some of the drawings were used on the back of each of

Photo: Communication activities with children near the River Llobregat.


Tips: 1. Identify or, if necessary, create a national group to assist in the realisation of fish pass projects. 2. Become familiar with the European working group on fish migration topics, e.g. EIFAC working group fish passes. 3. Learn from publications (scientific and popular) and newsletters on fish migration issues and consider producing your own. 4. Exchange information via the internet, e.g. look for internet orientated databases of issues and solutions.

project. In contrast there are clear risks in proceeding in any scheme without the necessary buy-in of all interest groups. It is not possible to identify a general approach to partnerships as every situation is different due to local factors such as the range of available partners, the potential solutions and their costs and local policy and available time. There are many differences between countries within the EU and often, between regions within a country. It is essential that there is a clear understanding of local issues and priorities before projects are promoted. Before approaching and engaging partners the objectives and potential areas for collaboration should be clearly identified. It is important to set out what could actually be achieved and to agree this before commencing a project. If different groups have differing objectives then it may not be realistic to proceed in a partnership.

7.2 COMMUNICATION WITH PARTICIPATING ORGANISATIONS There is a widespread and increasing focus on the promotion of partnership working to realise environmental improvements. Closer co-operation between government agencies, water companies and the public sector is essential if mutual interests and opportunities are to be identified and shared resources are used to address the environmental needs. This cultural change is clearly demonstrated in fisheries where interest groups including fishermen, private fishery owners and those interested in wildlife and biodiversity frequently have strong views about the needs to improve fish stocks and fish habitats. Strong partnerships allow more to be achieved than would otherwise be the case and usually ensures that the most cost effective decisions are taken.

The nature and extent of commitment from each partner should be identified, recognising that different partners can offer different levels and types of resource. For example some may offer technical knowledge whereas others may offer practical guidance, local information or offer the design and consultancy support that many fish pass schemes require. It should be an objective to maximise capacity through combining the different capabilities of each partner.

Photo: Education day at pumping station Rozema.

Identifying and engaging the range of public and private organisations and groups with an interest and a stake in planned management measures is important to encourage the sharing of views and values, a common understanding of the objectives and, ultimately, a shared vision of what is to be done. Early engagement encourages the sharing of ideas and approaches and can identify the optimum means of delivering a


Title Author Organisation Country

Sport fisheries and fish migration F. Moquette Dutch Angling Association The Netherlands

Angling organisations have always promoted fish migration. In 1911, Dutch and Belgian angling organisations first expressed their deep concerns about the planned construction of weirs without effective fish passes in the River Meuse. Eventually, but sadly, they were proved right when the Atlantic salmon died out in this river around 1950. For anglers it is important that fish can move freely to their spawning grounds and to maximise use of the habitat.

authorities, Sportvisserij Nederland is constructing a database based on maps and available data about the migration barriers for fish in the Netherlands (www.vismigratie.nl). Together with a number of Dutch and international partners a similar system is planned for the reintroduction projects and migration barriers for the salmon and other migratory species in the Rhine and Meuse rivers. Sportvisserij Nederland is the national body of 12 regional angling federations of which in total 400.000 anglers are member. It publishes a magazine for its anglers with a circulation of 100.000 to 500.000 copies, depending on the version. In this magazine there is frequently a strong emphasis on fish migration (www.sportvisserij nederland.nl).

This is based on the fact that “what is good for the fish is ultimately good for the angler”. Most species of fish migrate for several reasons and occur in almost every water system. Today fish migration is severely hampered or sometimes virtually made impossible by certain acts of construction or habitat manipulation and the final result is usually the same - a smaller or poorer fish population. The term ‘fish migration’ often evokes images of leaping salmon, but almost every species migrate over longer or shorter distances, from the tiny stickleback to the giant sturgeon. They all migrate to reproduce or simply to look for food. The migration of fish is therefore not unique to flowing waters. Because angling organisations are not responsible for the structure or management of waters, the Dutch national angling organisation ‘Sportvisserij Nederland’ (Dutch Angling Association) closely co-operates with other stakeholders and water management institutions to promote and restore the migration of fish.

Photo: Fishing is a popular form of recreation in The Netherlands.

Examples of this co-operation are: the Dutch Salmon platform (Platform for the restoration of the Atlantic salmon), ‘Zilveren Stromen’ (Silver Streams) and the ‘Vissennetwerk’ (Network for the fish). In co-operation with the Dutch water


Essential requirements from a successful partnership are: • Agreed objectives, set out clearly and fully described so that all partners have a clear understanding of them; • Continued focus on the objective as a reference point during the project so that progress will be tracked; • Clear areas of responsibility, with accountability, for each of the partners.

raise this issue and it is very important that this is done. The information provided should be appropriate for the part of society at whom it is aimed. In the first instance it may be necessary to provide information about the water cycle, how water is used and why it is important to manage it carefully. For other groups, specific requirements for biodiversity or for navigation might be more important. A strategy to achieve this improved understanding is vital to gain a shared understanding of problems and future priorities for action.

7.3 COMMUNICATION WITH MEMBERS OF THE PUBLIC Integrated water management does not relate only to the surface waters and banks of our channels, lakes and rivers, but also to the catchment area. Although the key interest groups can be readily identified, it is evident that the whole population of a river basin has a stake in projects to improve their own local environment.

By bringing the citizens to the concept of the water cycle, we bring improved understanding of that cycle to the citizens. Additionally, we bring awareness of environmental management problems as well as the measures to address them. Nowhere is this more apparent than in the concept of the river continuum for fish migration. It can not be ensured that the public appreciates and accepts the measures, but it is a step forward towards the understanding of water management and the importance of fish and fish migration in the shared environment.

The human population within a river basin forms a diffuse and extensive group. We believe that people should understand water management in outline and that specific measures to encourage fish migration should be publicised to improve public understanding of this specific issue.

7.4 EDUCATION In essence, environmental education is a result of education and up-bringing of people and of the accepted standards of local and national societies. The personal interests of those who are educating can assist this process, as enthusiasm is a good catalyst, but it may not be of importance. Our approach to education provides basic knowledge, but this needs to be balanced by experience that can only come from an ongoing lifelong learning process. Both are relevant for students to be able to form their own opinions, to recognise connections between facts and to learn how to make choices.

Similarly, it is important that professionals involved in water management seek and listen to the opinion of the public, whether this is from organised lobby groups or from individuals. This probably has never been more important than now as the full implications of the WFD start to become apparent. It is increasingly imperative to provide information to the public in a form that they can easily understand and which helps them to draw their own conclusions about priorities. If it is not explained that free migration of fish is prevented because of dams and weirs that do not contain fish passes, then it is unlikely that the issue will feature strongly in the minds of politicians. The WFD provides an important opportunity to

In relation to water management public education should include information about the water cycle and the vital importance of water for the environment and for society. Furthermore, this should include provision of information on fish


Title Author Organisation Country

Salmon homecoming project, Wales Peter Gough Environment Agency, Cardiff United Kingdom

To celebrate this and to engage the interest of communities in their local environment, the Salmon Homecoming Project was launched in schools close to the newly-accessible reaches of the river. The intention was to stimulate the interest of school children in the environment and in the biology of the salmon in their local rivers. We also wanted to demonstrate the importance of providing fish passes to allow the fish to distribute themselves in the catchment and in other schemes to improve the habitat for fish. The project also introduced children to the sport of angling as a worthwhile and healthy recreational activity.

In Wales, the Environment Agency runs a local “Salmon homecoming project”. This is an educational programme targeted at children aged 7-12 and it is intended to raise awareness of their local rivers and to generate an improved sense of “ownership” of their local river environment. The programme started after a new fish pass was constructed at Treforest weir, on the River Taff just north of Cardiff in south Wales. Since the 1980’s the river has rapidly recovered from over 100 years of industrial pollution and migratory salmonids have begun to recolonise the river. The large vertical slot fish pass allows migrating salmon, sea trout and also grayling and eel to ascend the river to the high quality spawning and nursery habitat upstream. More than 90% of the useable habitat is upstream of this weir and for the first time in over 200 years fish are able to reach these areas to spawn.






The children are given talks on the life cycle of salmon and an insight into the varied work of the Environment Agency fisheries department on local rivers. After this each school is given a mini-salmon hatchery containing all the equipment they need to rear about 200 salmon eggs in their classroom. The children look after the salmon eggs by monitoring the water temperature, changing the water when needed and checking the equipment whilst observing the developmental stages of the fish. When the salmon hatch out they are moved to larger tanks where they are reared to the first-feeding stage and they are then returned to the children so that they can release them into their local rivers. The event has proved to be very popular and the children have been very enthusiastic. They are particularly concerned about their fish and the condition of the river and have encouraged their parents and others to take more care of the river. The project has received good media interest and this has resulted in many more schools asking to be involved. We hope that this is the start of greater understanding, awareness and pride in the condition of their local rivers.




Tips on communication and education: 1. Identify shared objectives and interests as a basis for co-operation between organisations. 2. Organize special days to inform the public about fish and fish migration and provide practical demonstrations; In the Netherlands and the UK these days prove to be very effective. 3. Develop special fish migration games with the intention that children can learn while playing. Examples of these games are the Salmon game developed in Scotland and the Eel game developed in the Netherlands. 4. Water managers, nature conservation organisations, fishery boards, etc. should work together on education and the development of educational programmes and material. 5. Involving students in monitoring programmes can be an efficient way of conducting research. This is not only because of the cost efficiency aspects, but it also can prove to be a valuable training and development opportunity and an inspiring life time experience for the student themselves.

ecology and fish migration, the problems that are faced today in the specific area and the range of measures available to resolve these problems. There is growing experience that demonstrates how effective the provision of educational information for children can be. The use of fish within their local rivers as an indicator of local environmental quality can be a very powerful tool to motivate and enthuse children and in addition to encourage them to learn more. Increasingly this can form part of the formal educational syllabus in many countries and it is encouraging to feel that we could promote this further. The approach of the members of the Community Rivers project to education on fish migration is to involve children directly through provision of information and perhaps by guiding them along rivers. Their enthusiasm is a highly effective mechanism to engage their parents in achieving improved ownership and care for their local environment. Seeing healthy fish is a more evocative method of education for children than simply providing lists of facts on water quality standards!

Photo: Fish passes also provide an interesting playground for childen.


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durchgeführter Functionskontrollen an fischaufstiegsanlagen. –Institut für angewandte Ökologie, Kirtof-Wahlen,

Vannoote, R.L., Minshall, G.W., Cummins, K.W.,, Sedell, J.R. &

im Auftrag des ministeriums für Umwelt und naturschutz,

C.E. Cushing, 1980. The river continuum concept. Canadian

Landwirtschaft und Verbrauchershutz des Landes Nord-

Journal of Fisheries and Aquatic Sciences. 37, 130-37.

rhein-Westfalen (unveröffentlicht).

Vriese, F.T , J.C.A. Merkx & A.W. Breukelaar, 2006. Population

Sostoa, A. De., 1990. Peixos. Història Natural dels Països

study of female downstream migrating silver eel Anguilla

Catalans,12. Ed. Enciclopèdia Catalana 487 pp. Barcelona

anguilla in the Rhine system in 2005. VisAdvies BV, Utrecht.


Project VA2005_06, 67 pp.

Suomen ympäristökeskus, 1999. Kalateiden suunnittelu- ja

Woschitz, G., J. Eberstaller and S. Schmutz, 2003. Mindest-

mitoitusohjeet. Ympäristöopas 62. (a Finnish translation of

anforderungen bei der Überprüfung von Fischmigrationshilfen

the manual “Fischaufsteigsanlagen – Bemessung, Gestaltung,

(FMH) und Bewertung der Funktionsfähigkeit, Österreich-

Funktionskontrolle” by Deutscher Verband für Wasserwirt-

ischer Fischereiverband.

schaft und Kulturbau, 1996 - complemented with Finnish

Zitek, A. and S. Schmutz, 2004. Efficiency of restoration mea-

forewords by 1) Finnish Environment Institute and by 2)

sures in a fragmented Danube/tributary network. Proceedings

Anne Laine and Riitta Kamula (University of Oulu)).

of the fifth international conference on ecohydraulics - aquatic

Staub E. & Gerster St., 1992. Fischpassanlagen der Hoch-

habitats: analysis and restoration (12.-17. 09.04), Madrid.

rheinkraftwerke: Aufstiegskontrollen 1985/86 und Vergleich

Zitek, A., S. Schmutz and M. Jungwirth, 2004. Fischökolo-

mit früheren Erhebungen. BUWAL, Bern, Schriftenreihe

gisches Monitoring an den Flüssen Pielach, Melk und Mank

Fischerei Nr. 48: 1-109. http://www.umwelt-schweiz.ch/bu-

- im Rahmen des Eu-LIFE Projektes “Lebensraum Huchen”




Appendix I Contributors Austria


A. Zitek, [emailprotected]

T. Hakaste, tapio.hakaste@te-keskus.fi

and S. Schmutz, [emailprotected]

Hämeen TE-keskus/The Economic and employment centre

Institute for Hydrobiology and Aquatic Ecosystem

of Häme, Hämeen.

Management, University of Life Sciences, Vienna. A. Laine, anne.laine@ymparisto.fi Paul Jäger, [emailprotected]

North Ostrobothnia Regional Environment Centre, Oulu.

Government Land Salzburg, Department of Water Protection, J. Erkinaro, jaakko.erkinaro@rktl.fi


Oulu Game and Fisheries Research, Finnish Game and Fisheries Research Institute, Oulu.

Belgium-Flanders Saar Monden, [emailprotected]

J. Jormola, jukka.jormola@ymparisto.fi

The Flemish environment Agency, Water Department, Brussels.

and L. Järvenpää, lasse.jarvenpaa@ymparisto.fi Finnish Environment Institute, Helsinki.

Johan Coeck, [emailprotected] Anssi Eloranta, anssi.eloranta@ymparisto.fi

Research Institute for Nature and Forest, Brussels.

Central Finland Regional Environment Centre, Jyväskylä.

Czech Republic

Jarmo Kovanen, jarmo.kovanen@te-keskus.fi

D. Veselý, [emailprotected]

T & E Centre for Central Finland, Jyväskylä.

Povodí Moravy, Brno.

France Denmark

M. Larinier, [emailprotected]

G. Rasmussen, [emailprotected]

Conseil Supérieur de la Pêche-Cemagref, Soula.

Danish Institute for Fisheries Research (DIFRES), Departmeny og Inland Fisheries, Silkeborg.

Greece M. Koutrakis, [emailprotected]


National Agricultural Research Foundation (N.AG.RE.F.)

C. Lecour, [emailprotected]

– Fisheries Research Institute (F.R.I.), Kavala.

Lower Saxony Federal State Office for Consumer Protection and Food Safety, Institute for Ichthyology Department for

United Kingdom

Inland Fisheries, Hannover.

P. Gough, [emailprotected] R. Lemcke, roland.lemcke@fischerei.alr-kiel.landsh.de

and G. Armstrong,

Amt für Ländliche Räume, Abteilung Fischerei, Kiel.

[emailprotected] Environment Agency, Cardiff/Pembrokeshire.

U. Dumont, u.dumont@floecksmuehle.com Floecksmuehle Consultants, Aachen.



J. Huisman, [emailprotected]

G. Guti, [emailprotected]

Noorderzijlvest Water Board, Groningen.

and M. Pannonhalmi, [emailprotected] A.J. Scheper, [emailprotected]

Sturgeon 2020 Deposit Company, Györ.

Groningen- Drenthe Fishery Board, Tynaarlo.


M. Kroes, [emailprotected]

E. Pini Prato, enrico.pini@unifi.it

Visadvies (Fish Consultancy), Utrecht.

University of Florence, Department of Agricultural and Forest Engineering (DIAF), Florence.

Portugal C. Comoglio, [emailprotected]

J. Bochechas, [emailprotected]

Politecnico di Torino, Land, Environment And Geo-

and M. Santo, [emailprotected]

Engineering Department (DITAG), Turin.

Direcção Geral dos Recursos Florestais, Lisboa.



G. V. Ratkus, [emailprotected]

M. Ordeix, [emailprotected]

Lithuanian State Pisiculture and Fisheries Research Centre,

CERM, Centre d’Estudis dels Rius Mediterranis (Center for


the Study of Mediterranean Rivers), Fundació Museu Industrial del Ter (Foundation of the Industrial), Manlleu (Osona).


R. Casas, roser@parcfluvial.org

M. Lauff, [emailprotected]

Llobregat Fluvial Park, Berga.

and A. Hehenkamp, [emailprotected] Administration de la gestion de l’eau, Service pêche,

Estibaliz Díaz Silvestre, [emailprotected]


AZTI - Tecnalia / Unidad de Investigación Marina, Sukarrieta.

The Netherlands


J. van Herk, [emailprotected]

N. Lundh, niclas.lundh@fiskeriverket.se

Linkit Consult, Amsterdam.

and A. Johlander, arne.johlander@fiskeriverket.se Swedish Board of Fisheries, Gothenburg.

R. van Nispen, [emailprotected] Brabantse Delta Water Board, Breda.

Switserland F. Moquette, [emailprotected]

E. Staub, [emailprotected]

Dutch Angling Association, Bilthoven.

BUWAL, Fisheries Section, Berne.

M. Klinge, [emailprotected] Witteveen + Bos Consultancy, Deventer.

H. Wanningen, [emailprotected] P.P. Schollema, [emailprotected] and J. Kragt, [emailprotected] Hunze & Aa’s Water Board, Veendam.


Appendix II

Basic overview on information on the internet related to fish migration issues European – international information



Website with the environmental objectives, a gateway to

Website with information on the Community Rivers project.

information about Sweden’s environmental objectives and progress towards achieving them.

www.fao.org/fi Website of the Food and Agriculture Organisation of the United


Nations (FAO) and FAO fisheries department. The FAO is one

Database with bottlenecks for fish migration in Belgium (re-

of the largest specialised agencies in the United Nations system

gion of Flanders).

and the lead agency for agriculture, forestry, fisheries and rural development. The Code of Conduct for Responsible Fisheries


can be found on the website of FAO’s Fisheries Department:

website of the Environment Agency, United Kingdom, with

www.fao.org/fi/agreem/codecond/ficonde.asp. The website

information on fish, fishing and fisheries management.

of the EIFAC is: www.fao.org/fi/body/eifac/eifac.asp. www.umwelt-schweiz.ch/buwal/de http://europa.eu.int

Website of the FOEN, the federal government’s centre

Website about what the European Union does in by subject

of environmental expertise and is part of the Federal

(for example environment, nature and fisheries), the institu-

Department of the Environment, Transport, Energy and

tions and documents. The website is in all languages.

Communication of Switzerland. With information on fish, fisheries and fish migration issues. Downloads, e.g.:


ht tp ://w w w.umwe lt- s c hwe iz.c h /b uwa l /s hop /f i l e s /p d f /

A fishery projects portal and participatory resource gateway

phpg2IPgg.pdf?warenkorb = 48af02832ec79c415d318f38

for the fisheries and aquatic research and development sector.


oneFish also hosts the Fish Technology Knowledge Base. www.minlnv.nl www.dams.org

Website of the Dutch Ministry of Agriculture, Nature Man-

Website of the world commission in dams.

agement and Fisheries. It provides information regarding the Dutch policy to commercial fisheries. It provides several


publications on protection of fish.

Website of the International Association for Danube Research. www.dgrf.min-agricultura.pt

National information

Official website of the Portugese authority for inland fisheries.

www.ymparisto.fi Website of Finland’s environmental administration. A manual


(in Finnish, with English appendix) of environmental river en-

Portuguese database on fish presence/absence.

gineering including also the natural fish ways can be downloaded from: www.ymparisto.fi/default.asp?contentid=62769&lan=fi.


Scientific websites and organisations



Information on fish migration and design of fish way facilities

A non-profit making organisation committed to social and eco-

in Italy (e.g. pictures, photos and projects).

nomic development in the foodstuffs and fishing industries and to protection of the marine environment and of natural resources.


Specialising in the following three fields of activity: Oceanogra-

Flemish Marine Data and Information Centre (FMDC).

phy and Marine Environment, Fishing and Foodstuffs. www.difres.dk www.tecnalia.info

Danish Institute for Fisheries Research (DIFRES) is a research

A Technology Corporation made up of the AZTI, EUROPEAN

institution under the Ministry of Food, Agriculture and Fisheries.


DIFRES performs fisheries research in order to advice the Ministry of Food, Agriculture and Fisheries, public authorities,


international organisations, the industry and trade of fisheries

Website of Cemagref: Agricultural and environmental engi-

and other organisations. The Department of Inland Fisheries

neering research.

(www.difres.dk/ffi) focuses its research and advisory activities on two main topics, Freshwater Fish Biology and Fish Population


Genetics. The department is responsible for the management

LIFE-NATUR “Living space of the Danube Salmon” at the Rivers

of freshwater and diadromous fish species in Denmark.

Pielach, Melk and Mank. Link: Arbeitsgruppe: FISCHÖKOLOGISCHES MONITORING. Institute of Hydrobiology and Aquatic


Ecosystem Management, Department Water-Atmosphere-En-

KEMA is a commercial enterprise, specializing in high-grade

vironment, BOKU, Wien. For the Government of Lower Austria.

technical consultancy, inspection, testing and certification.



Website of the International Commission for the Protection of

The Netherlands Institute for Fisheries Research (known by its ac-

the Rhine. In French, German and Dutch.

ronym RIVO) located in IJmuiden and Yerseke. The new and definitive name will be: IMARES, Institute for Marine Resources & Eco-


system Studies. In IMARES, Alterra Texel, RIVO, as well as the Den

Website of the International Council for the Exploration of the Sea.

Helder location of TNO Ecological Risk Studies, have been joined.



Site with information for those who want to obtain information

Website for Fish Guidance Systems in the UK.

on tagging or marking of fish. The CATAG (Concerted Action for Tagging of Fishes) group has collected information on:


tags, tagging, experiments where tags are used, legislation

Website of Floecksmühle Consultancy, Germany, Aachen.

concerning tagging, health and behaviour changes, which can be induced by tagging and models used to work on data

Fisheries and angling organisations

from tagging experiments.

www.sportvisserijnederland.nl Website of the Dutch organisation of sport fisheries. It pro-


vides a database concerning fish migration in the Nether-

A database with information of 29300 Fish species, 216800

lands. www.vismigratie.nl

Common names, 41300 Pictures, 37900 References, 1340 www.eaa-europe.org

Collaborators, 20 million hits/month.

Website of the European Anglers Association. It provides inwww.fishri.gr

formation about fishing waters, fish biology, fishery manage-

Website of NAGREF-Fisheries Research Institute (Greece).

ment, environmental protection and restoration.


Colophon This guidance is a publication of the Interreg IIIC project “Community Rivers”. Interreg IIIC is a structural Funds programme of the EU that aims for a better co-operation between the members of the EU by increasing the effectiveness of existing policies and instruments for regional developments.

Text and coordination: M.J. Kroes1 H. Wanningen 2 P. P. Schollema 2 M. Ordeix3 D. Veselý 4 P. Gough 5

Edited by: P. Gough 5


VisAdvies BV (FishConsult), Utrecht, The Netherlands


Hunze en Aa’s Water Board, Veendam, The Netherlands


CERM, Centre d’Estudis dels Rius Mediterranis, Mannleu (Osona), Catalonia


Povodí Moravy, Brno, Czech Republic


Environment Agency, Cardiff, United Kingdom

Preferred citation: Kroes M.J., Gough P., Schollema P. P. & Wanningen H., 2006. From sea to source; Practical guidance for restoration of fish migration in European rivers.

Photography: We gratefully acknowledges all of the contributors, authors and partners of the Community Rivers project who gave us the permission to use their photographic material.

Cartography copyright page 6: © 2006 Philip’s, Octopus Publishing Group Ltd. London, United Kingdom.

Design: www.shapeshifter.nl, Utrecht, The Netherlands Copyright: Printing:

© 2006 Hunze en Aa’s

Plantijn Casparie Nieuwegein, The Netherlands

Postbus 195, 9640 AD Veendam, www.hunzeenaas.nl



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