Tuesday, June 5, 2007
542

Effects of large wood aggregations on brook trout distribution, trout diet, and invertebrate drift in six small Michigan streams

Andrea J. Fowler and Gary A. Lamberti. Biological Sciences, University of Notre Dame, 290 Galvin Life Sciences, Notre Dame, IN 46556

Trout stream restorations in Michigan’s Upper Peninsula often involve the addition of large wood to improve fish habitat, but local-scale effects of large wood remain understudied.  In six Michigan streams, we assessed fish distribution, drift composition, and Salvelinus fontinalis diet in pairs of 30-m reaches having either low or high volumes of wood.  Fish species were sampled using triple-pass electroshocking and stomach contents from up to 10 brook trout were collected from each reach by gastric lavage.  Brook trout in five streams were found in significantly higher numbers (p < 0.02) in low-wood reaches; in the sixth stream brook trout were found only in the high-wood area.  Diet analysis showed that stomachs of brook trout from low-wood reaches contained a significantly higher number (p < 0.03) of diet items than in the high-wood reaches, suggesting that wood abundance alters the density and composition of available invertebrate prey within a reach or the foraging ability of trout.  Overall results suggest that wood may interact with canopy cover to influence food availability and trout distribution, and contrast with previous studies indicating that brook trout prefer high-wood areas when choices are available.