engleski

Feeding ecology and trophic segregation of two sympatric shark species, Mustelus punctulatus and Squalus acanthias, in the north-central Adriatic Sea

We analysed the ecological roles and trophic interactions of two commercially important shark species, Mustelus punctulatus and Squalus acanthias, co–occurring in the shallow continental shelf of the north–central Adriatic Sea. We collected 185 M. punctulatus specimens (96 males and 89 females) and 157 individuals of S. acanthias (95 females and 62 males), obtained by on–board observers on commercial bottom trawls from April 2005 to April 2007. M. punctulatus dominantly preyed on benthic scavenger crabs like Liocarcinus depurator and Liocarcinus corrugatus, showed wide niche breadths and gradually specialized with increase in size. S. acanthias targeted small pelagic schooling fish like Engraulis encrasicolus and Sardina pilchardus, exhibited ontogenetic niche shift and extended its trophic spectrum with increase in size. Estimated trophic level (TL) for M. punctulatus was 3.69, while that of S. acanthias was higher (TL = 4.23). Dietary overlap was not significant between the species (Pianka’s overlap O = 0.55), except during spring season (O = 0.70) when both species selected small pelagic fish. Analysed shark species in the north–central Adriatic exhibited trophic segregation in resource partitioning, showed different feeding strategies and indicated that these predators should be managed separately.

diet composition; trophic niche; chondrichthyes; Mediterranean Sea

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