Forebay use and entrainment rates of resident adult fish in a large hydropower reservoir

Abstract

Fish entrainment occurs when individuals are displaced from reservoirs to downstream waters by way of water diversion through turbines or other water release structures. While much effort has been put into quantifying and reducing entrainment of downstream migrating salmonids, considerably less research has focused on fish that are residents in reservoirs and in many cases are the top piscivores in these systems. We used 2 yr of acoustic telemetry data on adult bull trout Salvelinus confluentus and burbot Lota lota tagged in Kinbasket Reservoir (British Columbia, Canada) to investigate entrainment vulnerability by measuring forebay use and entrainment rates. Our results revealed that (1) adult bull trout and burbot made little use of the forebay; (2) bull trout used the forebay more and had higher rates of entrainment than burbot; and (3) both forebay use and entrainment varied among seasons. Bull trout used the forebay more intensively and were mostly entrained in the fall and winter. Limited forebay use and entrainment data for burbot suggest that they are more vulnerable to entrainment in the fall. These findings should be generally applicable for adult bull trout and burbot in reservoirs that maximize operations in the fall and winter, and could help managers and industry to make informed decisions on how to mitigate and compensate for entrainment.