Diet and prey selectivity of the red mullet, Mullus barbatus (Pisces: Mullidae), from the southern Tyrrhenian Sea: the role of the surf zone as a feeding ground

The diet and prey selectivity of the red mullet, Mullus barbatus, on a sandy bottom of the Tyrrhenian Sea were examined, in respect of season, size and depth, focusing on the use of the surf zone as a feeding ground. Stomach contents of 99 specimens collected by beach seine (in the surf zone) and 568 specimens collected by trawl net (at 10, 20 and 30 m depths) were analysed. The overall diet of M. barbatus was dominated by crustaceans, mainly gammarids, while molluscs and polychaetes are secondary prey taxa. The diet composition of red mullet at each specific depth was related to the availability of prey in the benthic community: mysids were mostly preyed on in the surf zone, while gammarids, decapods and copepods were the principal crustacean prey organisms at other investigated depths. Red mullet in the surf zone mainly preyed on mysids and bivalves in summer and on cumaceans, gammarids and polychaetes in winter. At the other depths, seasonal variation in diet composition reflected the fluctuations of gammarid abundance in the environment; no differences in diet by size were detected. As a result, M. barbatus in the southern Tyrrhenian Sea can be considered as an opportunistic predator of benthic organisms, relying predominantly on crustaceans.