Feeding relationships among juveniles of abundant fish species inhabiting tropical seagrass beds in Cockle Bay, North Queensland, Australia

Abstract

Dietary analysis was conducted on juveniles of 10 numerically abundant fish species inhabiting tropical seagrass beds in North Queensland, Australia. Gammarid amphipods were consumed by all of the species, but their contribution to the diet of each varied. Crab larvae and copepods contributed to the diets of Leiognathus bindus, Pranesus endrachtensis and Stolephorus sp.; polychaetes and isopods were consumed by Sillago maculata burrus, Lethrinus sp., Pelates sexlineatus and Siganus canaliculatus; and Favonigobius reichei, Coris caudimacula and Arothron manilensis fed on bivalves. Seagrass and gastropods were rarely ingested by most of these fishes, but made a moderate contribution to the diet of A. manilensis. With the exception of L. bindus, the diet of each species was correlated with size: smaller species consumed copepods, crab larvae and gammarid amphipods, while larger species ate polychaetes, bivalves, isopods and gastropods. Non-metric multidimensional scaling (MDS) ordination plots emphasised the variation in dietary composition between species, and showed that this was often correlated with mouth length and width of the fish—for example, species with larger mouth dimensions tended to have broader diets. These interspecific differences in dietary composition increase the number of food resources available to these fishes, thereby reducing the potential competition for resources within the fish community.