Background. European hake, Merluccius merluccius, is a major predator in demersal ecosystem, and of great importance for the fishery. Knowledge of the feeding ecology of fish species is essential for implementing a multispecies approach to fishery management. Therefore this work was intended to analyse stomach contents and dietary changes according to fish size, season, sex, and depth to better understanding the ecological role of this species in Adriatic demersal marine communities.
Materials and methods.A total of 1646 specimens of hake were collected in the Adriatic Sea by oceanographic bottom trawl surveys carried out from 2005 to 2006 during summer-and winter seasons. Principal feeding indices, species diversity Bray-Curtis similarity index, feeding strategy plot, barplot on numeric, and weight abundance data were obtained in order to increase knowledge on the diet of hake.Results. The hake diet mainly consisted of crustaceans (particularly Decapoda) and teleosts (particularly European anchovy, Engraulis encrasicolus, and red bandfish, Cepola macrophthalma). Cluster analysis of %N (numeric prey abundance percent) showed different feeding habits of three mainly groups: small hakes (<150 mm), medium sized hakes (from 150 to 300 mm) and large hake (> 300 mm) from crustaceans (small specimens) to teleost fishes (medium and large specimens).
Conclusion.Feeding habits were size-dependant with fish diet being higher in stomachs of larger specimens. Feeding activity seemed to increase during growth, being smaller in immature individuals compared to adults, while no differences were found between females and males diet. Seasonal variation in diet showed an increase of teleost fishes in winter and crustaceans in summer.
Keywords:Merluccius merluccius, feeding habits, diet; northeastern Mediterranean Sea biology and current exploitation status are scarcely known (Arneri and Morales-Nin 2000) and no data as to its feeding habits in the Adriatic have been analyzed over the last thirty years (Stergiou and Karpouzi 2002). The purpose of this study was to determine the feeding habits and the trophic ecology of hake in the Adriatic Sea, northeastern Mediterranean. Our specific objectives were to examine the dietary changes according to fish size, sex, season, and depth to better understanding the ecological role of this species in Adriatic demersal marine communities.
MATERIALS AND METHODSSampling. European hake, Merluccius merluccius, were collected between 15 to 350 m depth along the coast of the Adriatic Sea (northeast Mediterranean) from the Gulf of Trieste to the Tremiti Islands (Fig. 1) Catches were frozen to prevent digestion of their stomach contents (Carpentieri et al. 2005) and finally taken to the laboratory. A total of 1646 specimens was collected. Hake were measured (total length, TL, in mm) and weighed to the nearest 0.1 g. Sex was determined macroscopically and specimens were classified as females (F), males (M), undetermined (U, macroscopically unidentifiable sex) and not determinable (ND, individual not e...