Prey selection by juvenile walleye as influenced by prey morphology and behavior

Mechanisms influencing selection of prey by juvenile walleye (Stizostedion vitreum; 100-210 mm) were examined in a series of laboratory experiments. Size preference was determined in aquaria (72 L) by introducing four to six individuals (5-mm length increments) of either bluegill (Lepomis macrochirus), gizzard shad (Dorosoma cepedianum), or golden shiner (Notemigonus crysoleucas) with a walleye from one of five length classes. Based on prey length, walleye selected smaller bluegill (20-32% of walleye total length) than either gizzard shad (24-33%) or golden shiner (38-43%). However, body depths of selected prey were similar across species (5-9% of walleye length). Preferences did not always agree with predictions from an optimal foraging model (handling time/prey dry mass), with walleye choosing larger prey based on both length and body depth. Species preference experiments in 2-m pools showed number of prey captures were higher for gizzard shad (76%) than for golden shiner (17%) and bluegill (7%). To explain differential prey vulnerability, observations of predator and prey behavior were conducted in a 750-L tank. Mean captures per strike were highest for gizzard shad (0.41), followed by golden shiner (0.32) and bluegill(0.13). Behavior and morphology, unique to each prey species, influenced walleye predation success.