Browsing by Author "Hamed, Salum Soud"

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    Feeding behaviour of spinner dolphins (stenella longirostris – gray, 1828 ) in Zanzibar coastal waters, Tanzania
    (University of Dar es Salaam, 2010) Hamed, Salum Soud
    The objective of this study was to investigate the foraging ecology of spinner dolphins (Stenella longirostris) in coastal waters of Unguja Island, Zanzibar. Dietary information was derived from the examination of stomach contents of 52 spinner dolphins collected from gillnet fisheries bycatch. The relative importance of each prey species was assessed through indices of relative importance. In total 10,270 prey items comprising 59 species of bony fishes and 3 species of squid were identified from food remains. Only four taxa contributed to the bulk of the stomach contents in more than 50% of the individuals: Myctophidae, Benthosema fibulatum (23.7 % by number (N); 21.7 % by mass (M), Sternoptychidae, Polyipnus indicus (12.8% N; 10.3% M), Sapidae, Sepia latimanus (12.0 % N; 10.4 % M) and Champsodontidae, Champsodon capensis (8.5 % N; 14.7 % M). There was significant difference in choice of food and size of prey species between mature male and female dolphins where mature males fed more on Benthosema fibulatum while mature females preferred to feed on Sepia latimanus. There was also a significant difference between immature and mature dolphins in the number of prey species in the diet where immature animals fed on fewer prey species. Ranking the importance of prey species showed that Benthosema fibulatum was the most important prey species for mature animals and Champsodon capensis the most preferred prey for immature dolphins. A comparison of the food preference between spinner and Indo-Pacific bottlenose dolphins (Tursiops aduncus) collected from the same geographical area indicates that the two species have little dietary overlap of fish species (4.5%) while greater overlap occur on cephalopods species (66.7%).