FOOD SEGREGATION OF SYMPATRIC MULLUS BARBATUS AND MULLUS SURMULETUS IN THE AEGEAN SEA

Abstract

This study analyzes the feeding habits of Mullus barbatus and M. surmuletus, which were found to co-exist in areas of different bathymetry in the central Aegean Sea. Smaller specimens, whose stomachs contained relatively more food in comparison to larger specimens, were found in shallower waters. Stomach content analysis of M. barbatus revealed that crustaceans, polychaetes, and bivalves were the most important prey categories, while M. surmuletus appeared to depend almost exclusively on crustaceans. The latter fact, as well as the fact that bottom sediment was not found in the stomachs of M. surmuletus, while such material appeared quite often in M. barbatus stomachs, suggests that the two species possibly adopt different foraging practices. A discrepancy in certain morphological characteristics associated with prey selection was found between the two species. Ontogenetic shifts appeared in the diet of both goatfishes; interspecific dietary segregation was more pronounced, however, in relation to ontogenetic changes in diet at the intraspecific level. Diet breadth of M. barbatus and M. surmuletus differed in relation to sampling site, as well as size of specimens. Segregation of the feeding niche between the two species possibly contributes to the reduction of interspecific competition, facilitating the coexistence of the two goatfishes in the oligotrophic Aegean Sea.