Size distribution of prey from the lake and in the diet of large (>350 mm) rainbow trout feeding on Oncorhynchus nerka were compared in two lakes. In both lakes, O. nerka made up >98% of the fish in both rainbow trout stomachs and midwater trawl catches. In Kootenay Lake, where there were no anadromous sockeye, kokanee (the nonanadromous morph) that were 100-200 mm fork length made up 42% of trawl catches, but in Quesnel Lake, which supports both kokanee and a large run of anadromous sockeye, trawl catches consisted of 95% age 0+ O. nerka (<80 mm fork length). Although the size of prey in Quesnel Lake (104 mm) was smaller than in Kootenay Lake (139 mm), most of this difference appeared to be due to differences in the size of the trout predators which averaged 540 mm in Quesnel Lake and 713 mm in Kootenay Lake. Few fry (<80 mm) were observed in the stomach samples of rainbow trout caught in either lake. In both lakes, the largest prey taken by rainbow trout predators were less than about 1/3 of the predator le
Parkinson, Eric A., Hume, Jeremy M.B.; Dolighan, Robert. 1989. Size Selective Predation by Rainbow Trout on Two Lacustrine Oncorhynchus nerka Populations. Ministry of Environment. Fisheries Management Report. FMR94
Topic: Fish and Fish Habitats
Keywords: rainbow trout, kokanee salmon, sockeye salmon, prey, predation, Kootenay Lake, Quesnel Lake
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