RELATIONSHIP OF FOOD-HABITS TO YELLOW PERCH GROWTH AND POPULATION-STRUCTURE IN SOUTH-DAKOTA LAKES

We compared summer yellow perch (Perca flavescens) food habits among a wide range of perch population types in six South Dakota lakes. Chiro nomids were a major dietary component in all populations with mean rel ative importance (RI) values ranging from 29 to 55. Corixids were a ma jor diety component for high-quality (large proprtion of fish greater than or equal to 200 mm TL) yellow perch populations, with mean RI val ues ranging from 22 to 26. Zooplankters were important sources of prey for yellow perch in low-quality (low proportion of fish greater than or equal to 200 mm TL) populations, with mean RI values ranging from 3 5 to 51. The fast growth of yellow perch in high-quality populations w as attributable to a diet in which macroinvertebrates, specifically ch ironomids, amphipods and corixids, were the primary prey. Fish were no t a substantial component of yellow perch diets in situations were per ch attained large size (greater than or equal to 300 mm) and experienc ed fast growth. A significant negative correlation existed between yel low perch mean back-calculated length at age 3 and the mean RI of zoop lankton (r=-0.87, P=0.02). The mean RI of macroinvertebrates was posit ively correlated with yellow perch growth rates (r=0.86, P=0.03) while there was not a significant correlation between the mean RI of fish a nd perch growth rates (r=0.66, P=0.16).