| Summary: | I examined food habits, degree of fullness, fecundity, the spawning cycle, and incidence of lamprey scarring of burbot (Lota lota) in Wisconsin waters of Green Bay and Lake Michigan. I examined food habits and incidence of lamprey scarring of lake trout (Salvelinus namaycush), and evaluated the overlap in diet between burbot and lake trout. The diets of burbot and lake trout were examined with respect to month of capture, capture method, depth of capture, area of capture, and total length. I recorded the incidence of intestinal parasites of the phylum Acanthocephala from eight species of Lake Michigan fish. The diet of burbot and lake trout were 93 and 99% fish by volume, respectively. Percent volumes of identified fish eaten by burbot and lake trout were respectively: alewife 18, 33; rainbow smelt 14, 23; bloater 7, 13; cottus sp. 6, 1; deepwater sculpin 4, <1; yellow perch 4, 0; other fish 4, 2. Diets of burbot and lake trout examined by month of capture, capture method, depth of capture, area of capture, or length of predator were variable. The differences in diet were significant for burbot with respect to month, method, depth, and length. The differences were not tested for lake trout, or for burbot by area of capture. Fullness indices revealed that burbot ate more food in October through January and in April through May, than during other times of the year. The linear food selection index indicated that alewives and bloaters were preferred by lake trout, and burbot preferred sculpins. avoided by both predators. Rainbow smelt were moderately The diets of burbot and lake trout seemed to overlap at only moderate levels. Burbot appeared to be size selective for some fish species, but not for all. Lake trout were size selective for all prey species. Both burbot and lake trout ate greater numbers of prey as they grew. The mean diameter of burbot eggs, measured from 17 individuals, was 0.75 mm and the mean number of eggs was 1,179,881. The largest burbot were not necessarily the most fecund. Mean gonadosomatic indices (GSI) of burbot ranged from a low of 1% in July to a high of 15% in January. Maximum GSI for an individual burbot was 32% for a female, and 37% for a male. The sea lamprey marking rate for fish examined in the laboratory was 1.4% for burbot and 9.9% for lake trout. Burbot examined live in the field exhibited a marking rate of 4.5% The mean number of acanthocephalans per fish in the intestines of 8 species of Lake Michigan fish ranged from 11 in lake whitefish to 350 in chinook salmon. A trend of increasing numbers of acanthocephalans with increasing host size was evident only for burbot. University of Wisconsin Sea Grant program, Salmon Unlimited and Trout Unlimited.
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