DIETS OF SISCOWET LAKE TROUT FROM THE APOSTLE ISLANDS REGION OF LAKE SUPERIOR, 1993

Stomach contents of 384 siscowet lake trout (Salvelinus namaycush sisc owet) from the Apostle Islands region of Lake Superior were examined t o determine if diets exhibited seasonal trends or shifted with predato r size. The information was also used to qualitatively compare siscowe t and lean lake trout (S. namaycush) diets. Stomachs from siscowet les s than 500-mm total length (TL) contained primarily macroinvertebrates (clams, Mysis relicta, and insects), sculpins (Cottidae; mean TL = 45 mm), and coregonines (Coregonus spp.; mean TL = 120 mm). Stomachs fro m siscowet between 500- and 699-mm TL contained items similar to small er siscowet, but burbot (Lota lota; mean TL = 162 mm and a 254-min sis cowet were also present. Stomachs from siscowet longer than 699-mm TL contained fishes such as burbot (mean TL = 246 mm) and coregonines (me an TL = 240 mm). Dietary proportions of coregonines increased signific antly with increasing siscowet length groups. The proportion of the to tal number of identified taxa and frequency of occurrence of terrestri al insects and sculpins declined significantly across all length group s between June and December. Siscowet and lean lake trout diets were n ot found to be substantially different and a potential for competition exists.