Understanding temporal variability in fish and eel movements to minimise the likelihood of entrainment at water pumping stations

Norman, Josh

Biological sciences
October 2019

Thesis or dissertation

© 2019 Josh Norman. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder.

Rivers in the United Kingdom have been subject to extensive modification to meet societal demands for navigation, drinking water, industry, hydropower, drainage, and abstraction. This heavy pressure on river resources has resulted in many constrained rivers becoming vulnerable to flooding and the majority of heavily modified rivers require active flood risk management. Subsequently, there is now a focus on water pumping stations (WPS) that use pumps to control inland water levels. However, these WPS carry a dangerous risk of entrainment (entry into pumps) to riverine fish, and entrainment of fishes through pump intakes is a major cause of mortality in coarse fish populations throughout the UK. Additionally, recruitment of the European eel (Anguilla Anguilla) has declined by up to 90% since the 1980s and there is now a legislative requirement to increase eel escapement at WPS. Knowledge of the temporal movements of fish around WPS is required to protect the critically endangered European eel and prevent entrainment of coarse fish. In the present study, an underwater sonar (DIDSON) was utilised to examine temporal (diel and seasonal) patterns in fish activity at Foss WPS, York, England, with an overall aim to determine whether temporal fish movements can be used to minimise fish entrainment at WPS. A five month deployment (N = 153 nights) of a DIDSON successfully imaged thousands of coarse fish and captured downstream movements of European eels (N = 2). Sonar images revealed clear modulated diel patterns in fish movements where activity was highest at dawn and dusk periods, and during the day. But, this was followed by a period of unpredictability throughout winter, and a linear regression model revealed a potentially unpredictable fish population. In all cases, fish activity was significantly different between months, and was highest during the day. These findings suggest that temporal variation in fish movements can be used to inform pump operation such that entrainment of fish is minimised, providing an increased understanding of fish behaviour around WPS, and arguing a demand for more detailed biological assessments to be undertaken at WPS.

Department of Biological & Marine Science, The University of Hull
Bolland, Jonathan D.
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