FISH PASSES - Design, Dimensions and Monitoring

Design, Dimensions and Monitoring

Food and Agriculture Organization of the United Nations
Deutscher Verband fr Wasserwirtschaft und Kulturbau e.V. (DVWK)
Rome, 2002

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The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.

The designations ‘developed’ and ‘developing’ economies are intended for statistical convenience and do not necessarily express a judgement about the stage reached by a particular country, territory or area in the development process.

The views expressed herein are those of the authors and do not necessarily represent those of the Food and Agriculture Organization of the United Nations.

DVWK ISBN 3-89554-027-7
FAO ISBN 92-5-104894-0
DVWK ISSN 0722-7167

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Fish passes Design, dimensions and monitoring.
Rome, FAO. 2002. 119p.


Key words: fish pass; fishway; fish ladder; technical fish passes; close-to-nature types; hydraulic calculation; upstream migration; free passage; river rehabilitation; restoration; longitudinal connectivity; monitoring

Many fish species undertake more or less extended migrations as part of their basic behaviour. Amongst the best known examples in Europe are salmon (Salmo salar) and sturgeon (Acipenser sturio), which often swim several thousands of kilometres when returning from the sea to their spawning grounds in rivers. In addition to these long-distance migratory species other fish and invertebrates undertake more or less short-term or small-scale migrations from one part of the river to another at certain phases of their life cycles.

Fish passes are of increasing importance for the restoration of free passage for fish and other aquatic species in rivers as such devices are often the only way to make it possible for aquatic fauna to pass obstacles that block their up-river journey. The fish passes thus become key elements for the ecological improvement of running waters. Their efficient functioning is a prerequisite for the restoration of free passage in rivers. However, studies of existing devices have shown that many of them do not function correctly. Therefore, various stakeholders, e.g. engineers, biologists and administrators, have declared great interest in generally valid design criteria and instructions that correspond to the present state-of-the-art of experience and knowledge.

The present Guidelines first refer to the underlying ecological basics and discuss the general requirements that must be understood for sensible application of the complex interdisciplinary matters. These general considerations are followed by technical recommendations and advice for the design and evaluation of fish passes as well as by proposals for choosing their hydraulic dimensions correctly and testing the functioning. Fishways can be constructed in a technically utilitarian way or in a manner meant to emulate nature. Bypass channels and fish ramps are among the more natural solutions, while the more technical solutions include conventional pool-type passes, slot passes, fish lifts, hydraulic fish locks and eel ladders. All these types are dealt with in this book. Furthermore, particular emphasis is laid on the importance of comprehensive monitoring.

These Guidelines deal with mitigation of the upstream migration only as data on improvement of downstream passage was scarce at the time of the preparation of the first edition, published in German in 1996. Therefore, the complex theme of downstream migration is only touched on but not developed in depth.


Part I   (713 Kb)

1   Introduction

2   Ecological principles

2.1   Running water ecosystems
2.2   River continuum
2.3   Biological zoning of running waters
2.4   Potentially natural species composition
2.5   Migration behaviour of aquatic organisms
2.6   Hazards to aquatic fauna caused by dams and weirs
3   General requirements for fish passes
3.1   Optimal position for a fish pass
3.2   Fish pass entrance and attraction flow
3.3   Fish pass exit and exit conditions
3.4   Discharge and current conditions in fish pass
3.5   Lengths, slopes, resting pools
3.6   Design of the bottom
3.7   Operating times
3.8   Maintenance
3.9   Measures to avoid disturbances and to protect the fish pass
3.10 Integration into the landscape

Part II   (616 Kb)

4   Close-to-nature types of fish passes

4.1   Bottom ramps and slopes
4.2   Bypass channels
4.3   Fish ramps
4.4   Hydraulic design

Part III   (842 Kb)

5   Technical fish passes

5.1   Pool pass
5.2   Slot passes
5.3   Denil pass
5.4   Eel ladders
5.5   Fish lock
6   Monitoring of fish passes
6.1   Objective of monitoring
6.2   Methods
6.3   Assessment of results
7   Legal requirements
7.1   New installations
7.2   Existing installations

Part IV   (181 Kb)

8   References

9   Table of symbols and signs

10  Glossary

      Photo credit


      Overview of the most frequently used
      construction types of fish passes