Gape limitation and piscine prey size-selection by yellow perch in the extreme southern area of Lake Michigan, with emphasis on two exotic prey items

The trophic linkage between yellow perch Perca flavescens and two exotic prey items, alewife Alosa pseudoharengus and round goby Neogobius melanostomus, was investigated in the extreme southern area of Lake Michigan during the summer of 2002. Yellow perch 100mm total length, LT (n1⁄4 1293) exhibited size selective feeding, with 148 fish containing round gobies and 120 fish containing alewives. The mean round goby LT, preyed on by yellow perch, was 23% of the predator LT, with a range of 7 to 47%, and mean alewife LT was 32% of yellow perch LT, with a range of 18 to 46%. Although the selection of prey size by yellow perch increased proportionally with yellow perch LT, prey consumed appeared smaller than theoretically possible based on gape size. # 2005 The Fisheries Society of the British Isles