Impacts of Recovering Walleye Populations on an Altered Forage Fish Community

Abstract

This study was designed to characterize the available forage base and predatory demand by walleye in Saginaw Bay to deduce impacts of their consumption on the forage fish community during May through September 2009. Walleye relied heavily age-0 yellow perch and round goby, a reflection of the fish community abundance in 2009, to achieve observed growth. In conjunction with observed growth and monthly diet data, a walleye population size range was estimated based on minimum, mean, and maximum fishing mortality rates documented by MDNR over a 23-year period and the known number of walleye harvested in 2009 to model range of predatory demands. Based upon the predatory demand range calculated for the walleye population estimates compared to the range of prey population estimates, walleye consumption did not appear to play a significant role in age-0 and -1+ yellow perch mortality in 2009. However, other species like emerald shiner, rainbow smelt, round goby, and salmonids had periods of strong predation pressure and were possibly controlled by walleye. These other prey species provided alternative forage for the walleye and buffered yellow perch from strong predation pressure that has been observed in other systems when yellow perch were abundant.