Biotic influences on habitat selection by young-of-year walleye (Stizostedion vitreum) in the demersal stage

Abstract

The influence of prey availability and predation risk on the distribution of young-of-year (YOY) walleye (Stizostedion vitreum) was investigated by comparing species associations with the relative abundance of YOY walleye across nine habitat types using an underwater visual assessment technique. During the early demersal period (mid-June to mid-July), YOY walleye were found primarily in areas of high macrophyte cover at 2–5 m depth. YOY walleye abundance was positively correlated with the abundance of prey fishes at this time. YOY walleye shifted to low-cover, shallow areas during the late demersal period (mid-July to late August), and the significant prey associations disappeared. Although the selected habitats are considered to have low predation risk, the distribution of YOY walleye was not related to our index of predator abundance in either time period. YOY walleye were not observed in three of the nine habitat types, suggesting that active habitat selection was occurring. High macrophyte cover and prey availability appear to be the major factors influencing habitat selection during the early demersal period. Although our results do not demonstrate the functional significance of the shift of YOY walleye into shallow water, we hypothesize that these habitats are selected as refugia from particular predators such as adult walleye.