Food habits of nonnative Walleyes in Lake Pend Oreille, Idaho.

This article focuses on assessing the ecological effects of an established nonnative Walleye (Sander vitreus) population in the Lake Pend Oreille (LPO) system, Idaho. Using stomach content and stable isotope analyses alongside bioenergetics modeling, the study found that Walleyes consumed a diverse diet dominated by kokanee (Oncorhynchus nerka), native cyprinids, and catostomids, with kokanee representing the largest proportion of energy intake, especially in older fish. Walleyes occupied trophic positions similar to other top piscivores, and their consumption of kokanee was estimated at over 27,000 kg annually, potentially impacting salmonid populations important for fisheries and conservation. The findings highlight spatial, seasonal, and ontogenetic variation in Walleye diets and underscore the potential for direct predation and competition with native and nonnative salmonids, as well as notable consumption of native nongame fishes, informing management strategies aimed at balancing recreational fisheries and native species conservation in western freshwater systems.