Resource partitioning along three niche dimensions in a size-structured tropical fish assemblage

In Tissawewa, a tropical reservoir, the size-specific resource use of the 10 most important fish species was determined along three dimensions: trophic, spatial, and temporal. During this study, a drought occurred distinguishing two periods before and after the drought that differed markedly in availability of resources and fish biomass. In this study, differences in resource use between the two periods are presented together with their consequence on the partitioning of resources. A different approach is introduced into the calculation of niche breadth and niche overlap incorporating size-specific differences in resource use and interactions between resource dimensions. Comparison with conventional measures of niche breadth and niche overlap shows that conventional measures often misrepresent interactions between species. Condition and biomass were used as indicators of a species' fitness, and it is shown that fitness of most species is governed by the availability of resources and partitioning of these resources is an important mechanism allowing potential competitors to coexist. Resource partitioning along the trophic dimension was more important than along the spatial or temporal dimension.