DIET OF BURBOT IN GREEN BAY AND WESTERN LAKE MICHIGAN WITH COMPARISONTO OTHER WATERS

We determined foods eaten and factors influencing the diet of burbot ( Lota lota) and compared our results with those of other studies to hel p assess the role of burbot in the fish community of Lake Michigan. We examined stomachs of 3,570 burbot of 215-845 mm total length caught b y 10 methods from 5 areas of Green Bay and western Lake Michigan in de pths of 1 to 160 m during September 1986 to November 1988. Fish compos ed 94% of the volume of the diet; percent volumes of fish identifiable to genus or species were alewife (Alosa pseudoharengus), 31; rainbow smelt (Osmerus mordax), 25; bloater (Coregonus hoyi), 13; sculpins of the genus, Cottus, 11; deepwater sculpin (Myoxocephalus thompsoni), 8, yellow perch (Perca flavescens), 8, other fish, 5. Cottus spp. were m ore important than their volume indicated because they were the most f requently were Mysis relicta, found in 26% of the burbot containing fo od, and Pontoporeia hoyi. The diet varied with size of burbot, i.e., i nvertebrates were more important for the smaller burbot, and with area and depth of capture. Alewives were more important at depths of 20-39 m than at shallower and deeper depths. In waters exceeding 40 m depth the diet of burbot in Lake Michigan seemed to have changed little sin ce the 1930s, and it was similar to the diet of burbot in Lake Superio r in the 1960s. Foods commonly important for burbot in many waters in North America are sculpins, coregonids other than lake whitefish (Core gonus clupeaformis), Pontoporeia spp., M. relicta, and yellow perch, a nd crayfish outside of the Great Lakes. Trout and salmon (Salmo spp., Salvelinus spp., Oncorhynchus spp.) and suckers (Catostomus spp.) were inconsequential in the diet of burbot in Lake Michigan, and they have not been found to be important in the diet of burbot in other studies .