Summer Food of Lake Whitefish, Coregonus clupeaformis Mitchill, from Heming Lake, Manitoba

Abstract

During the summer months of 1956 to 1959 inclusive, the stomach contents of 2963 Heming Lake whitefish from 5–15 inches in length were examined. Data on stomach contents of 194 whitefish taken in 1945 were examined and included in this analysis. Most stomachs contained food, but lesser quantities of food per stomach and many empty stomachs were found in July and August of each year. Mayfly nymphs occurred in the stomachs most often. Other, insects eaten included dipterous larvae, especially Chaoborus and chironomids. Incidental items, constituting a smaller though important part of the fish's diet, included aquatic coleopterans, hemipterans, trichopteran larvae, cladocerans, Hyalella, hydrachnids, gastropods and, seasonally, aerial insects from the surface of the lake, and small fish. Cyclopid and calanoid copepods were found in about 1% of the stomachs. This apparently low incidence of cyclopids in the diet is considered to be sufficient to establish the relatively high infection levels of Triaenophorus found in Heming Lake fish. Some differences in diet between fish of different sizes and between seasons were shown.