DIETS OF LAKE TROUT INHABITING NEARSHORE AND OFFSHORE LAKE-MICHIGAN ENVIRONMENTS

Stomach contents of sport-caught and gill net-captured Lake Michigan lake trout (Salvelinus namaycush namaycush) (n = 2,032) were analyzed to compare the food habits of nearshore shallow water and offshore deep water trout. Alewife (Alosa pseudoharengus) was the primary forage of nearshore (n = 112) and midlake reef fish (n = 59) collected in 1980, constituting 84 and 89 percent by number of the diets respectively. Nearshore lake trout taken from the sport catch from 1984-88 (n = 1,045) had diets dominated by alewife, averaging 81 percent of the total number of prey fish consumed each year. Lake trout gillnetted from 1985-88 in the Clay Banks Reef area (n = 380), a series of shallow nearshore reefs, had diverse diets, with rainbow smelt (Osmerus mordax) averaging 64 percent by number of the prey fish consumed annually. Lake trout gillnetted from 1985-88 on Sheboygan Reef (n = 536), a deep offshore reef which is part of a midlake reef complex, had diets composed mainly of bloater chub (Coregonus hoyi), which averaged 78 percent of the total number of prey fish consumed each year. Results suggest lake trout food habits are more responsive to changes in prey abundance relative to other salmonine predators, and that stocking lake trout on deep offshore reefs will increase the species use of abundant bloater chub stocks.