Influence of Food Competition, Predation, and Cannibalism on Walleye (Stizostedion vitreum vitreum) and Sauger (S. canadense) Populations in Lake of the Woods, Minnesota

Abstract

Feeding relationships between walleye, Stizostedion vitreum vitreum, and sauger, Stizostedion canadense, in Lake of the Woods, Minnesota, were investigated. Effectiveness of food consumption estimates in measuring feeding interactions was defined. Differences in walleye and sauger distribution, food habits, and feeding strata reduced interactions. Walleye feeding rate varied from 0.5 to 4.1% of body weight per day and was limited by prey abundance during June and July. Higher August and September prey densities did not influence walleye food consumption. Daily food consumption of sauger varied from 0.5 to 3.5% of body weight independent of changes in food availability. Relationships between the number of prey consumed daily by walleye and sauger and the decline in abundance of prey species suggested that predation was important in controlling food availability, and was the major cause of food competition and its limiting effect on walleye growth.Analysis of commercial catch statistics suggested that factors other than predation influenced walleye survival. However, the relationship between the number of young-of-the-year walleye consumed and their abundance in the lake demonstrated predation by sauger may be important to walleye survival.