Use of Gill Nets for Target Verification of a Hydroacoustic Fisheries Survey and Comparison with Kokanee Spawner Escapement Estimates from a Tributary Trap

Abstract The focus of this study was to determine whether gill nets are a valid method for assessing species composition for a hydroacoustic survey and whether the hydroacoustic and gill-net survey could be used to forecast the spawn escapement of kokanee Oncorhynchus nerka so as to allow fisheries managers to plan ahead for egg takes at Sullivan Lake, Washington. We conducted a mobile hydroacoustic survey of the limnetic zone of Sullivan Lake in September 2003. Species composition was estimated using floating, sinking, and suspended horizontal and vertical gill nets. Spawning escapement was estimated from a weir, trapping, and carcass recovery effort in Harvey Creek, the only spawning tributary of Sullivan Lake. Fish captured in gill nets ranged from 110 to 579 mm total length (TL), but 82% of the fish captured were between 150 and 290 mm TL. Kokanee were the dominant fish species captured in the limnetic gill nets, comprising 77% of the fish captured between 150 and 290 mm TL and 90% of the fish capture...