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Feeding ecology and trophic segregation of two sympatric mesopredatory sharks in the heavily exploited coastal ecosystem of the Adriatic Sea

We investigated ecological roles and trophic interactions of two commercially important mesopredatory shark species, Squalus acanthias and Mustelus punctulatus that co–occur on the continental shelf of the north–central Adriatic Sea. Both shark species are feeding specialists, with significant dietary overlap recorded only during spring season. The two species of sharks showed different patterns of feeding as they grew: S. acanthias extended its trophic niche with increase in size, while M. punctulatus developed a more specialized diet with growth. These two sharks partition the food resources and reduce the niche overlap by foraging at different trophic levels. Mustelus punctulatus is a crustacean feeder, specialized for foraging on scavenging malacostracans frequently found along trawl tracks or discards in the Adriatic fishing zone. On the other hand, S. acanthias prefers small pelagic fish which are commercially exploited and in decline. Different foraging strategies adopted by these two species suggest that they should be managed separately. Dietary specialisation, direct competition with humans for its main prey, and higher intrinsic vulnerability make S. acanthias particularly susceptible to the impact of anthropogenic perturbations.

diet composition ; Elasmobranchii ; endangered species ; Mediterranean Sea ; trophic niche

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