PREY CONSUMPTION BY THE BURBOT (LOTA-LOTA) POPULATION IN GREEN BAY, LAKE-MICHIGAN, BASED ON A BIOENERGETICS MODEL

We estimated prey consumption by burbot (Lota lota) based on diet, mor tality, growth, maturity, thermal history, population density and a bi oenergetics model derived for a similar, cold-water gadoid, the Atlant ic cod (Gadus morhua). In Green Bay, Lake Michigan, burbot >400 mm fed primarily on fish; smaller burbot probably fed mostly on invertebrate s and sculpins (Cottus sp.). Our calculations indicate that burbot of age greater than or equal to 1 consumed 16 kg/ha of prey (12.2 kg/ha o f fish) in 1988 in the Wisconsin waters of Green Bay including 3.3, 2. 1, 1.9, 1.2, and 0.8 kg/ha of rainbow smelt (Osmerus mordax), sculpins , alewife (Alosa pseudoharengus), yellow perch (Perca flavescens), and bloater (Coregnus hoyi), respectively. On an areal basis, piscivory b y burbot in Green Bay was higher than the reported lake-wide average f or consumption by all salmonids in Lake Michigan. Burbot consumed abou t 25% of the lake-wide salmonid consumption of alewife per unit area a nd close to the estimated combined commercial and sport harvest of yel low perch in the Bay the same year (271 vs. 325 tons). Thus, burbot sh ould be included when considering the balance between predatory demand and forage fish production in Green Bay and probably also in other ar eas of Lake Michigan.