engleski

Feeding habits of predatory thermophilic fish species from recently extended distributional range in northeast Adriatic Sea, Croatia

The widening range of distribution of thermophilic fish species has been noticed in the northern parts of the Mediterranean, including the Adriatic Sea. It was observed that predatory thermophilic species, for example bluefish Pomatomus saltatrix, adapt well to conditions in new habitats and form large populations in the northernmost part of the Adriatic. Recent studies suggest an increased presence of the greater amberjack, Seriola dumerili, the Mediterranean barracuda, Sphyraena sphyraena, the leerfish, Lichia amia and incidence of pompano, Trachinotus ovatus, common dolphinfish, Coryphaena hippurus, and P. saltatrix in the northeast Adriatic Sea (Istria, Bay of Medulin). These species were completely unknown for Istrian coast until the end of the 20th century. Although, some of investigated species are not real “alien” this research could help in understanding impact of global warming on species shifting ranges. Information on their diet in recently extended distributional range in the eastern Adriatic Sea are completely missing. Hence, dietary assessment was performed using frequency of occurrence (F%), numerical frequency (N%) and mass frequency (W%) in the Bay of Medulin during 2017, 2018 and 2019. In total, 219 specimens were captured and analysed. The index of relative importance IRI was calculated for each prey category. Diet overlap was calculated using Schoener’s index, based on IRI. The main foods for C. hippurus were European pilchard, Sardina pilchardus, and common squid, Loligo vulgaris. P. saltatrix consumed unidentified species from Sparidae family and T. ovatus crustaceans from Mysidacea family. Different species from genus Atherina represented important foods for L. amia, S dumerili and S. sphyraena. Great importance for L. amia represented fishes from family Sparidae, for S. sphyraena from Carangidae family and for S. dumerili from Clupeidae and Muliidae family. Analysis of diet overlap based on IRI suggests no diet overlap between analysed thermophile species from Medulin Bay. Based on presented results it appears that these species found different trophic niches, but knowledge of their impact on the entire community remains unknown.

marine fish ; extended distributional range ; North Adriatic ; Istria

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