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The University of Southampton

Research project: Improving fish passage at low-head river barriers

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In the UK, thousands of manmade in-river structures (e.g. dams, weir, and culverts) are restricting the movements of ecologically and economically important fish species. Such habitat fragmentation can have profound ecological effects on fish populations and community structure, necessitating the development of more effective multi-species fish passage solutions.

Manmade in-river barriers may prevent, limit, confuse, and delay the movements of fish; leading to increased energetic costs, predation risk, and fragmentation of populations. Improving the pass-ability of these barriers for fish has been highlighted as a priority in many River Management Plans. A migratory species featured heavily throughout this body of research is the European eel (Anguilla anguilla). The European eels stock is considered outside safe biological limits and the current fishery unsustainable. Further, an EU “eel” directive (Council Regulation 1100/2007/EC) requires each member state to prepare eel management plans (EMPs). Mitigating the impact of in-river barriers on upstream eel migrations has been highlighted as an important strategy for aiding stock recovery.

This project will address a number of key issues relating to fish passage by; 1. Developing low-cost modifications to Flat-V gauging weirs, enabling more efficient fish passage while not compromising the hydrometric properties of the weir (i.e. its ability to accurately gauge flow); 2. Assessing the functionality and efficiency of eel specific fish passes, and 3. Investigating novel fish pass solutions (e.g. baffle designs) for culverts which are less likely to foul with debris and lead to flooding.

This experimental research project is funded by the Environment Agency and being conducted in large open-channel flumes at the University of Southampton. Application of this research will help mitigate anthropogenic impacts to aquatic environments and aid the conservation of our freshwater fish.

Eel specific fish pass solution - 'Eel tiles'
Eel specific fish pass solution
Spoiler baffles in an experimental culvert
Spoiler baffles

Related research groups

International Centre for Ecohydraulic Research
Water and Environmental Engineering Group
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