Journal Article
Direct and indirect impacts of pumping station operation on downstream migration of critically endangered European eel
Jonathan D. Bolland; Leona A. Murphy; Robert J. Stanford; Natalie V. Angelopoulos; Nicola J. Baker; Rosalind M. Wright; Jake D. Reeds; Ian G. Cowx
Fisheries Management and Ecology · Vol. 26, Issue 1 · pp. 76-85 · 2019
Abstract
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.