SEASONAL-VARIATION IN FOOD-RESOURCE PARTITIONING OF 5 FISH SPECIES IN RELATION TO PREY AVAILABILITY

We observed that yellow perch, Perca flavescens, golden shiner, Notemigonus crysoleucas, spottail shiner, Notropis hudsonius, and log perch, Percina caprodes, partitioned food resources in relation to resource abundance in a small bay of Lake Saint-Pierre, Quebec. When the abundance of benthic resources was at its lowest, in May 1988, the fish showed a very low overlap in their diet. In contrast, when these resources were most abundant, in August 1988, the four species had a high degree of food overlap. Two other sampling periods, in June and July, revealed intermediate situations. A fifth species, the silvery minnow, Hybognathus nuchalis, was phytophagous and, therefore, did not compete with the other species for food resources. An ecomorphological analysis of the first four species suggests that these partition food resources according to their functional morphology. Our results support Schoener's hypothesis, which states that the intensity of interspecific competition, in terms of resource partitioning, varies according to the abundance of these resources.