UNEQUAL COMPETITOR IDEAL FREE DISTRIBUTION IN FISH

Key predictions of unequal competitor ideal free distribution models w ere tested using a continuous input situation. Ten individually identi fiable cichlid fish competed for food items at either end of their tan k. Their distribution fitted the predictions of the equal competitor, continuous input ideal free model almost perfectly. However, examinati on of individual intakes revealed significant variation in individual success and relative competitive ability between patches. Contrary to expectations, fish did not exclusively use the patch where their intak e was higher, although individuals experiencing greater differences in intake rate between patches were more selective. We found no evidence for a truncated distribution or even a correlation between competitiv e ability and patch quality. Changing the input regime to reduce compe tition did not produce a decrease in the range of intake rates between individuals. This study indicates the value of future empirical and t heoretical work on how relative competitive ability varies with the na ture of the foraging environment.