Largemouth bass predation effect on stocked walleye survival in Illinois impoundments

Survival of stocked fish can be mediated by biotic factors such as size and species, predators, and prey, and abiotic influences such as temperature and habitat. Walleyes Sander vitreus are numerically among the most stocked fish in the USA, yet stocking success of this species is highly variable. We examined the effects of predation by largemouth bass Micropterus salmoides on walleyes across 77 stocking events in 10 Illinois impoundments. Predation mortality was assessed by examining diets of largemouth bass for up to 21 d post walleye stocking. Of 8,591 largemouth bass diets examined, 2.0% contained walleye, corresponding to 4.3% walleye mortality attributable to largemouth bass predation. Largemouth bass predation was greatest within 24 h of stocking, and no predation was observed after 14 d. Predation mortality and fall CPUE of walleyes were related to largemouth bass density; however, we found no relationship between predation mortality and fall CPUE of walleyes. Our results suggest that predation by largemouth bass, a widespread and abundant predator, has a negligible effect on walleye stocking success in Illinois impoundments.