Stranded Kokanee Salvaged From Turbine Intake Infrastructure Are At Low Risk For Reentrainment: A Telemetry Study In A Hydropower Facility Forebay

Entrainment at hydropower facilities, where fish (volitionally and nonvolitionally) enter hydropower infrastructure such as intake towers, can lead to fish becoming stranded for considerable periods of time rather than being flushed to downstream areas. To reduce fish injury and/or mortality from entrainment stranding events, hydropower operators will salvage stranded fish and release them back into the upstream reservoir. We documented the postrelease movements of salvaged fish to determine their vulnerability to reentrainment at a large hydropower facility. Kokanee Oncorhynchus nerka were collected from the turbine intake towers at the W. A. C. Bennett Dam in northeastern British Columbia, surgically implanted with small acoustic transmitters, and released in the forebay area of the hydropower facility. Fish movements were tracked using an array of hydrophones in the forebay area. While the depths and hydraulics of the forebay resulted in low detection efficiency of the receiver array, detection data for 25 fish revealed that 72% (n = 18) of fish were last detected at hydrophones located >1,000 m from the turbine intakes (considered low risk to restranding or reentrainment), 24% (n = 6) of fish were last detected at hydrophones <500 m to the turbine intakes (considered vulnerable to restranding), and one reentrainment event (n = 1; 4% maximal entrainment rate) was observed. Our results indicate there is a low risk associated with kokanee reentrainment events at this large hydropower facility and that manual salvage appears to be a reasonable approach to mitigate fish loss.