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 segregation were mainly used to determine potential competitors for food. Diet and microhabitat segregation were demonstrated in all four assemblages. In one of the assemblages we observed little partitioning of resources among two filamentous algae feeders. The role of competition for food is discussed on the basis of fluctuations in diet overlap in relation to seasonal changes in food supply. Diet overlap proved to be highest in periods of food abundance. This is in concordance with the hypothesis that competition decreases in case of food abundance. Furthermore, we compared fish densities between assemblages, because competition would regulate density. We found that diets were most diverse in the assemblage with lowest fish density, while interspecific differences in diet were smallest. Food seems not to be limiting in this particular assemblage, and factors other than competition for food are probably more important in regulating density here.