Effect of habitat selection and behavior on vulnerability to predation of introduced fish

Losses from resident predators can be an important source of mortality for introduced fish, but may vary among species. I compared vulnerability between muskellunge (Esox masquinongy) and walleye (Stizostedion vitreum) to predation by largemouth bass (Micropterus salmoides). In pool experiments (N = 51) with simulated vegetation, muskellunge were more susceptible to predation than walleye. Habitat selection explained some of these differences as walleye spent more time in the simulated vegetation and associated with the substrate than muskellunge. Expectations from pool experiments were confirmed in reservoirs stocked with two size groups of walleye (N = 8 introductions) and esocids (N = 20). Walleye were less susceptible to largemouth bass predation for both small (mean 14% of stocked fish) and large (mean 0%) size groups than were small (mean 36%) and large (mean 21%) esocids of three taxa. For muskellunge only, walleye were less vulnerable to predation for large size groups, but not for small ones. Predation from largemouth bass should be a more important source of poststocking mortality for esocids than for walleye in lakes and reservoirs. Largemouth bass population demographics, specific to each system and year, should be considered more carefully in determining where esocids should be introduced than for percids.