title: Feeding ecology and trophic segregation of two sympatric mesopredatory sharks in the heavily exploited coastal ecosystem of the Adriatic Sea.
abstract: The 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 were investigated. Both shark species are dietary specialists, with a significant dietary overlap recorded only during the spring season. They showed different patterns of feeding as they grew: S. acanthias extended its trophic niche with an increase in size, while M. punctulatus developed a more specialized diet. These two sharks partition food resources and reduce niche overlap by foraging at different trophic levels. Mustelus punctulatus is a crustacean feeder, specialized in foraging on scavenging malacostracans frequently found along trawl tracks or on discards in the Adriatic fishing zone. Conversely, S. acanthias prefers small pelagic fishes, which are commercially exploited and in decline. The different foraging strategies adopted by these two species suggest that they should be managed separately. Dietary specialization, direct competition with humans for prey and their higher intrinsic vulnerability make S. acanthias particularly susceptible to the effects of anthropogenic perturbations.
authors.affiliation: Department of Biology, Faculty of Science, University of Zagreb, Rooseveltov trg 6, 10000, Zagreb, Croatia.
authors.forename: R
authors.initials: R
authors.lastname: Gračan
authors.affiliation: Center for Marine Research, Ruđer Bošković Institute, G. Paliaga 5, 52210, Rovinj, Croatia.
authors.forename: D
authors.initials: D
authors.lastname: Zavodnik
authors.affiliation: Public Institution for Managing Protected Nature Areas, Grivica 4, 51000, Rijeka, Croatia.
authors.forename: P
authors.initials: P
authors.lastname: Krstinić
authors.affiliation: Institute of Oceanography and Fisheries, Šetalište I. Meštrovića 63, 21000, Split, Croatia.
authors.forename: B
authors.initials: B
authors.lastname: Dragičević
authors.affiliation: Department of Biodiversity, Faculty of Mathematics, Natural Sciences and Information Technologies, University of Primorska, Glagoljaška 8, 6000, Koper, Slovenia.|Marine Science Program, Juraj Dobrila University of Pula, Zagrebačka 30, 52100, Pula, Croatia.
authors.forename: B
authors.initials: B
authors.lastname: Lazar
mesh_terms: D000818:Animals; D004032:Diet; D017753:Ecosystem; D005247:Feeding Behavior / Q000502:physiology*; D009752:Nutritional Status; D009792:Oceans and Seas; D012621:Seasons; D012754:Sharks / Q000502:physiology*; D013045:Species Specificity; D061350:Sympatry / Q000502:physiology
keywords: Elasmobranchii; Mediterranean Sea; diet composition; endangered species; trophic niche