Direct and indirect impacts of pumping station operation on downstream migration of critically endangered European eel

• Published in: Fisheries management and ecology Vol. 26; no. 1; pp. 76 - 85
• Main Authors: Bolland, Jonathan D., Murphy, Leona A., Stanford, Robert J., Angelopoulos, Natalie V., Baker, Nicola J., Wright, Rosalind M., Reeds, Jake D., Cowx, Ian G.
• Format: Journal Article
• Language: English
• Published: Oxford Wiley Subscription Services, Inc 01.02.2019
• Subjects: Acoustic telemetry; Acoustics; Axial flow; Axial flow pumps; catadromous; Catadromous fishes; Catadromous migrations; Catchment area; Catchments; Downstream; downstream migration; Eels; Endangered species; entrainment; Escapement; fish passage; Imaging techniques; Injury prevention; Marine fishes; Migration; multi‐beam sonar (ARIS); Pumping; Pumping stations; Survival; Telemetry; Transponders; Upstream; Water levels; Water management
• ISSN: 0969-997X; 1365-2400
• DOI: 10.1111/fme.12312

Downstream passage of European eel Anguilla anguilla (L.) in catchments with pump(s) for water level management is a major concern. Catchment‐wide acoustic telemetry revealed silver eels quickly migrated downstream through unobstructed reaches (n = 12; mean ± SD = 17.9 ± 1.9 km/day). Fourteen of 17 acoustic‐tagged eels detected at the pumping station (82.1%) retreated back upstream and ten (58.8%) passed through pumps after delays (9.5 ± 11.0 days). Multi‐beam sonar imaging across the intake screen (55‐mm gaps) revealed that peaks in migration occurred during the nights preceding the new moon but 76.7% retreated back upstream. All passive integrated transponder (PIT)‐tagged eels recaptured (n = 56) downstream of a large (2.23‐m diameter) mixed flow pump survived but 96.5% had minor injuries, reduced physical condition and/or abnormal behaviour. By contrast, 64.7% of PIT‐tagged eels recaptured (n = 17) downstream of a small (0.8‐m diameter) axial flow pump died. No acoustic‐tagged eels that passed through the small axial flow pump (n = 10) performed onward migration at sea, unlike “control” eels released downstream (n = 11). This evidence may help develop effective remediation measures, such as operational changes, to maximise escapement of catadromous eel species at pumping stations.