Niche segregation among Lake Malawi cichlid fishes? Evidence from stable isotope signatures

The fish communities of the rocky littoral zone of Lake Malawi contain a la rge number of ecologically similar cichlid species. It has been suggested t hat dietary niche segregation may play a role in the coexistence of these s pecies, but previous studies have yielded ambiguous results. Stable isotope analysis was used to determine whether five sympatric species are segregat ed by diet. Significant differences were found between the mean isotopic si gnatures of the study species, but there was considerable interspecific ove rlap between three species from the same subgenus that were anatomically al most indistinguishable. The implication that this was due to substantial di etary similarity was supported by stomach content analysis. We propose that ecological segregation may not always be necessary to allow coexistence of Lake Malawi cichlids.