Understanding behavioural ecology of river-resident fish in winter to improve protection at water pumping stations

Norman, Josh

Abstract

Globally, there is a reliance on water pumping stations to manage river levels and prevent flooding in heavily-modified anthropogenic rivers. Pumping stations damage longitudinal and lateral river connectivity and their operation presents a major risk of mortality to river-resident fish via entrainment into pumps, which could have population-level effects. Fish are attracted to pumping stations for refuge from predators in pumped catchments with heavily degraded river habitats. However, the operational management of pumping stations rarely includes ecological considerations for river-resident fish and there is a lack of information on how to protect these species. In order to make informed decisions for mitigating the negative impacts of pumping stations and provide effective protection, a thorough understanding of the behavioural ecology of river-resident and their interactions with pumping stations is required. This study investigated the factors affecting ecological behaviours of river-resident fish at three different pumping stations. The potential for operational management changes and the provision of alternative habitats to provide protection was also investigated.
Multi-beam sonar (Dual-Frequency Identification Sonar: DIDSON) was used at an off-channel flood-relief pumping station on the Yorkshire Ouse to investigate diel movements of river-resident fish in response to temperature, hydrology and pump and flood gate operation, and to determine a fish-friendly operational regime. Lateral movements of fish between the main-river and off-channel area were predominantly during the crepuscular period and daytime. Seasonal and inter-annual variations in diel movements were strongest during a baseline year with no pump operation and was influenced by cooling temperatures. A Generalised Linear Mixed Model (GLMM) suggested fish entered the off-channel area when river levels were stable and not when they were rising or falling. Two years of impact data revealed pump operations severely disrupted the regular ecological functions of local fish populations. Modifying when pumps operate to reduce entrainment and modifying floodgate operations appeared to be a promising management option to prevent immigration of fish into the hazardous off-channel area.
At Bourne Eau (Tongue End) pumping station, which is located at the downstream extent of a heavily degraded single-thread system, the temporal rate of predator-prey interactions, the attack behaviour of predators, and the refuge seeking behaviour of prey was investigated using DIDSON. River-resident fish experienced temporally dynamic species-specific predation risks from two dissimilar predators (i.e., aquatic vs aerial), pike and cormorant. Non-consumptive predation effects were evidenced by quantified changes to shoal structure (density, area) and both shoaling (group aggregation) and schooling (coordinated directional movement), including diurnal migrations and use of a pumping station intake as refuge, were the primary ways in which prey managed predation risk. Consequently, it was concluded that prey fish were paradoxically dependant on a hazardous pumping station for refuge from predators which proposed important considerations for how Flood Risk Management (FRM) on lowland rivers can influence the ecological interactions between piscivorous predators and their prey.
Avian predation at pumping stations could be managed by addressing habitat loss caused by River Maintenance Measures (RMMs) associated with FRM requirements. To investigate the potential for protecting river-resident fish in pumped catchments using habitat restoration techniques, common roach (Rutilus rutilus) habitat choice between an artificial habitat and simulated pumping station was tested in controlled conditions with an iterative experimental design. All roach occupied a simulated pumping station rather than open water during baseline observation. Half of the fish did not respond to the provision of artificial habitat and occupancy of artificial habitat was influenced by overhead shelter. After habitat management, i.e., physical exclusion from the pumping station, roach preferred artificial habitat rather than the pumping station and this persisted once access to the pumping station was reintroduced. Therefore, these findings suggest appropriate habitat management is required to accompany habitat restoration plans to protect river-resident fish that occupy pumping stations.
Catchment-wide distribution and abundance of river-resident fish in a pumped flood-relief lowland Fenland drain (North Level Drain) and at artificial habitat designed to provide predator and flow refuge for river-resident fish occupying Tydd pumping station was examined before and after a major flood event using side-scan sonar. Sonar surveys pre-flood found highly abundant aggregations of river-resident fish (approximately 1 km upstream of Tydd pumping station) but North Level Drain was void of fish post-flood. When artificial habitats (installed for predator refuge) were monitored pre-flood, fish abundance followed a crepuscular pattern and was comparable between three different artificial habitat structures. Artificial habitats monitored post-flood were void of fish. Overall, these findings suggest that flood-relief pump operations could significantly alter distribution and abundance of river-resident fish upstream of pumping stations and artificial habitat introduction has the potential to provide protection for river-resident fish.

Citation

Norman, J. Understanding behavioural ecology of river-resident fish in winter to improve protection at water pumping stations. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4291429

• Thesis Type: Thesis
• Deposit Date: May 16, 2023
• Publicly Available Date: May 16, 2023
• Keywords: Fisheries
• Public URL: https://hull-repository.worktribe.com/output/4291429
• Award Date: Sep 1, 2022