RESOURCE PARTITIONING AMONG ROCK-DWELLING HAPLOCHROMINES (PISCES, CICHLIDAE) FROM LAKE VICTORIA

Resource partitioning was studied on four assemblages of haplochromine cichlids at rocky islands in the southern part of Lake Victoria. The emphasis was put on diet segregation, while data on microhabitat segre gation were mainly used to determine potential competitors for food. D iet and microhabitat segregation were demonstrated in all four assembl ages. In one of the assemblages we observed little partitioning of res ources among two filamentous algae feeders. The role of competition fo r food is discussed on the basis of fluctuations in diet overlap in re lation to seasonal changes in food supply. Diet overlap proved to be h ighest in periods of food abundance. This is in concordance with the h ypothesis that competition decreases in case of food abundance. Furthe rmore, we compared fish densities between assemblages, because competi tion would regulate density. We found that diets were most diverse in the assemblage with lowest fish density, while interspecific differenc es in diet were smallest. Food seems not to be limiting in this partic ular assemblage, and factors other than competition for food are proba bly more important in regulating density here.