Experimental quantification of the response of fish to conditions associated with low-head hydropower and fish passage facilities

Abstract

This thesis assessed the impact of a novel low-head hydropower device, the Hydrostatic Pressure Converter (HPC), on downstream moving fish, and investigated factors that may limit both up- and down-stream fish pass efficiency. This was achieved through the use of a blade strike model (BSM) and experimental studies conducted in large open channel flumes. A BSM predicted a lower probability of strike with a HPC blade for small fish that travelled downstream faster, and when blades rotated slowly. A major pinch-point between the blade tips and the base of the flume caused severe damage to euthanized brown trout (Salmo trutta) as they passively drifted through a prototype HPC. Damage ranged from abrasive scale loss to skeletal deformation and breakage. Rainbow trout (Oncorhynchus mykiss) and European eel (Anguilla anguilla) did not exhibit avoidance behaviours when approaching the intake to a HPC located within a flume. When behavioural data (speed of downstream movement and orientation) were incorporated into BSM simulations, probability of strike increased and decreased for trout and eel, respectively, compared with an assumption of passive drift with bulk flow. Species specific behaviours influenced probability and severity of strike with a HPC blade. Management recommendations are made to ensure HPC developments meet the required environmental standards. Ensuring efficient fish passage around low-head hydropower developments presents a major ecological challenge. Behavioural data on individual fish encountering conditions ubiquitous to fish pass structures was used to investigate and identify factors that may limit passage efficiencies. Although upstream migrant adult river lamprey (Lampetra fluviatilis), a species of conservation concern in Europe, were predicted to avoid areas of elevated turbulence, little evidence in support of this was found. Instead lamprey appeared to alter their migration strategy based primarily on water velocity. Behaviours were indicative of a time conservation strategy, i.e. altering behaviour to expedite passage through energetically expensive environments. For downstream moving fish, delay due to avoidance of conditions created at bypass entrances (e.g. abrupt accelerations of velocity) can negatively impact fitness. Velocity gradients created by a constricted flume section had a clear influence over downstream moving brown trout. Avoidance behaviours occurred at a similar threshold spatial velocity gradient when dark (ca. 0.4 cm s-1 cm-1), and the addition of a light stimulus served to reduce this threshold by approximately 50%. Elevated avoidance to velocity gradients was also evident when downstream migrant juvenile salmon (Oncorhynchus tshawytscha) were able to navigate using mechanosensory and visual senses. Avoidance behaviour significantly impacted subsequent rate of passage. Information provided in this thesis significantly enhances our understanding of how fish respond to environmental stimuli, has direct application to fish passage, and the potential to improve fish survival at low-head hydropower developments.

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Identifiers

ORCID for Andrew Vowles: orcid.org/0000-0001-8253-5938

ORCID for P.S. Kemp: orcid.org/0000-0003-4470-0589

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