engleski

Diet of the bottlenose dolphin (Tursiops truncatus, Montague, 1821) in the Adriatic sea.

The bottlenose dolphin (Cetacea: Delphinidae) is considered to be the only marine mammal with resident population in the Adriatic Sea. The diet of the Adriatic population is poorly known and the aim of this study was to determine intraspecific differences, correlate them with ecological caracteristics of the prey species and consider if the species is an opportunistic feeder. Stomachs of bottlenose dolphins stranded along Croatian coast in the period of 1990-2004. (n=50) were examined. 26 contained food remains. 1 contained only milk and remaining stomacs (n= 25) contents were analysed to the lowest taxonomic level using published guides, reference otolith and cephalopod beak collections. Total number of prey items was 234. Fish were the most important prey (n=114) with 16 determined species, followed by cephalopods (n=80). Bivalvs and Gastropods were found in a single speciment, that died of lead poisoning following a gunshot. The most frequent prey species were arbun, šarun, hake and muzgavac. Intraspecific differences were found regarding sex and geographical location. Females had higher frequency of cephalopods than males and more benthic cephalopods, suggesting that females and males differ in exploitation of resources, which is in consistency with the data from the Mediterranean Sea. Comparison of three regions in the Adriatic Sea shows that the population in the middle Adriatic feeds primarily on cephalopods, while the northern and the southern population prey primarily on fish. It is posible that the large number of cephalopods in the diet of the middle adriatic bottlenose dolphins is due to the large abundance of cephalopods in the area, which suggests opportuistic feeding. Hake frequency reduction untill 2000. corresponds to reports on hake biomass, which was dropping untill 2000. That suggests that prey abundance may affect prey composition of bottlenose dolphins in the Adriatic Sea.

bottlenose dolphin; diet; pray species

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