NICHE SEPARATION BETWEEN COLONIZING AND INDIGENOUS GOATFISH (MULLIDAE) ALONG THE MEDITERRANEAN COAST OF ISRAEL

The present study assesses the resource partitioning between two Red Sea colonizers, the goldband goatfish Upeneus moluccensis and the brownband goatfish U. pori, and the two indigenous Mediterranean goatfishes, the red mullet Mullus barbatus and the striped mullet M. surmuletus, along the Mediterranean coast of Israel. Niche separation was studied along three axes: habitat selection, feeding habits and spawning season. Habitat selection is the most significant parameter separating the species. The two colonizing species occupy a shallow habitat, U. pori dominating the primarily sandy bottom at 20-30 m and U. moluccensis at 40-50 m, at which depth the sea bottom becomes increasingly silty. Of the two indigenous species, M. barbatus is dominant in depths below 55 m, while M. surmuletus appears at low abundance in all depths. Niche separation by feeding habits is much less evident. All four species feed primarily on macrurid crustaceans and thus the values of diet overlap are rather high (0.666 less-than-or-equal-to T less-than-or-equal-to 0.928). Prey size is not an important factor in niche separation. Young fishes (S.L. less-than-or-equal-to 115 mm) of all four species feed upon prey of similar size (20-160 mg). Among older individuals (S.L. > 115 mm) three species continue to feed upon the same size prey, while U. moluccensis feeds upon considerably larger prey (600-2200 mg). The difference between the spawning seasons of the colonizing vs indigenous species and consequent timing of benthic settling may contribute to niche separation. The results of this study suggest that success in colonization by Red Sea goatfish may be due to the existence of unexploited niches in the eastern Mediterranean ecosystem.