Oral Presentation International Conference on River Connectivity (Fish Passage 2018)

The behaviour of downstream migrating silver European eels immediately upstream of a pumping station with a traditional trash rack (#179)

Leona Murphy 1 , Ros Wright 2 , Jake Reeds 2 , Ian G Cowx 1 , Jon Bolland 1
  1. University of Hull International Fisheries Institute (HIFI), Hull, YORKSHIRE, United Kingdom
  2. Environment Agency, Norwich, England

Many lowland rivers around the world are regulated by pumping stations to protect land and property from flooding. Critically endangered European eels (Anguilla anguilla) that inhabit catchments regulated by pumping stations will inevitably encounter such structures during their downstream spawning migration to the Sargasso Sea. However, the response of eels when encountering pumping stations and the effect on their natural migratory behaviour remains largely unknown. During this investigation, a multi-beam sonars (ARIS) imaged 362 eels approaching a pumping station trash rack (55-mm bar spacing) during pump operation. Of these eels, 278 (76.7%) retreated back upstream, 65 (17.8%) passed through the screen and the route out the ARIS beam could not be determined for 19 eels (5.2%). Of the eels that retreated back upstream, 126 (45.3%) performed a startle or avoidance response when approaching the screen, 141 (50.7%) touched the screen and 11 (4.0%) both avoided the screen and touched it before retreating. Eels approached the pumping station almost exclusively at night, and thus it is unlikely the eels were able to visually identify the screen. Findings relating to the part of the trash rack the eels approached, distance from the trash rack when they performed a startle or avoidance response, factors influencing the type and strength of the response and the extent of searching behaviour before retreating upstream will be presented. This knowledge about eel behaviour at pumping stations is essential for us to determine how to increase downstream passage for this critically endangered species, especially given current European legislation (EC Eel Regulation (1100/2007)) currently states water intakes abstracting greater than 20 m3 a day should have fine-mesh screens.