Title: Fish Pass Design for Eel and Elver
Author: D J Solomon
Author: M H Beach
Author: Environment Agency
Document Type: Monograph
Annotation: Environment Agency Project ID:EAPRJOUT_1229, Representation ID: 399, Object ID: 2443
Abstract:
In 2001 the Environment Agency produced its National Eel Management Strategy against a backdrop of a decline in European eel recruitment which has been apparent for the past twenty years or more. Restricted access to potential rearing areas is considered to be a factor in this decline, and there is no doubt that man-made obstructions to migration and dispersion are limiting eel stocks in many parts of the UK and Europe. The strategy states that the Agency will seek to both encourage and fund the construction of eel passes to restore access to areas where it has been denied or restricted by artificial barriers. The overall aim of this study is to produce design criteria and best practice designs for eel and elver passes. This Technical Report uses a review of eel biology and existing installations to develop design criteria for passage facilities for eels and elvers. It should be read in association with the Manual which sets out specific design criteria for eel and elver passes. Types of obstruction where passage facilities might be required include tidal barrages, tidal flaps, mill weirs, gauging weirs, amenity barrages and weirs, navigation weirs, dams for reservoirs or HEP, diversion dams or weirs, water intake weirs and fish counting structures. As passes can also be utilised as traps for monitoring purposes this potential is also explored in the study. This report presents a detailed review of those aspects of the biology and lifehistory of the eel that influence migratory behaviour. These include the seasonal timing of migration, effects of water temperature, river discharge, light, tide, lunar cycle and time of day on migratory activity, climbing ability, dispersion and rate of upstream migration, vulnerability to predation, sizes of fish involved, and swimming ability. From this a series of biological and non-biological design criteria are developed for upstream passage facilities for eels and elvers. A similar approach is used to develop design criteria for the protection of downstream migrants. The report briefly explores fundamental approaches to providing upstream passage facilities as an introduction to the analysis of existing installations. These are channel passes, pass-traps, pumped-supply passes, pipe passes, lifts and locks, easements, and removal of the structure. The fundamental approaches to protection of downstream migrants are also discussed. Existing installations at about 35 sites in England, France and North America are described and assessed. Details of their approach to providing benign conditions for passage, construction and operation are presented, with an assessment of their strengths and weaknesses. Basic design guidelines are produced from a synthesis of the review of eel migratory behaviour and the analysis of existing eel passes. These include fundamental design considerations, siting of facilities, facilities based on R and D Technical Report W2-070/TR1 substrates, facilities based on easements and anaturala channels, pipe passes, lifts and locks, upstream outlet arrangements, monitoring facilities, trap and transport, passage of eels through passes designed for other species, attraction flows, constraints at gauging structures, tidal barriers, maintenance and health and safety considerations, and protection of downstream migrants. Particular attention is paid to facilities based on substrates as this is the most usual approach. Considerations include types of substrate, slope, length of passes and resting places, width and depth, flow down the pass, changes in tailwater and headwater levels, and cover against light and predation.
Publisher: Environment Agency
Subject Keywords: Fish passes; Rivers; River fisheries; Migration; Brackishwater environment; Freshwater ecology
Taxonomic Keywords: Anguilla anguilla
Extent: 105
Permalink: http://www.environmentdata.org/archive/ealit:4662
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