An Analysis of the Feeding Habits of Rainbow Trout and Lake Trout in Birch Lake, Cass County, Michigan

In Birch Lake, an oligotrophic lake in southwestern Michigan, rainbow trout (Salmo gairdnerii) and lake trout (Cristivomer namaycush) have been stocked at various times in an effort to make the deeper waters of the lake provide more fishing. Over a 6-year period, creel-census clerks collected stomachs of 322 rainbow trout and 25 lake trout taken by anglers. Analysis of the contents of these stomachs revealed that while the two species of trout were competing with each other for food, neither species preyed upon the indigenous cisco population nor competed with it for food. Aquatic insects and fish made up the greater part of the diet of both species of trout. The fish portion of the diet consisted largely of forage species, with yellow perch and centrarchids occurring but seldom in the stomachs. Rainbow trout took very little surface food except during late June, when there was a mass emergence of burrowing mayflies, and in October and early November when many terrestrial insects were consumed.