THE FORAGING ECOLOGY OF 2 PAIRS OF CONGENERIC DEMERSAL FISH SPECIES -IMPORTANCE OF MORPHOLOGICAL-CHARACTERISTICS IN PREY SELECTION

The feeding habits of two sympatric species pairs of demersal fish (Mu llus barbatus-Mulhus surmuletus, Serranus cabrilla-Serranus hepatus) w hich occupy the shallow coastal area (25-30 m) in Iraklion Bay were in vestigated from samples collected on a monthly basis (August 1990 to A ugust 1992). Stomach content analyses revealed that ail of them were c arnivores, feeding mainly on benthic invertebrates, and that each spec ies consumed a narrow range of prey species with no significant dietar y overlap. The morphology of their feeding apparatus was compared to e xamine the effect of any morphological differences on food selection a nd resource partitioning between the fish species. The species could b e distinguished on the basis of the size of their mouth gape, the numb er of gill rakers and the length of their intestine. This study shows that each species pair follows a different strategy segregating along food niche dimensions. In particular, M. barbatus and M. surmuletus se gregate their feeding niche consuming different prey taxa with similar sizes whereas S. cabrilla and S. hepatus differ considerably with res pect to the degree to which prey species contribute to their diets cou pled with differences in mean prey sizes. (C) 1997 The Fisheries Socie ty of the British Isles.