Stomach contents of stranded cetaceans along the Sea of Oman and the Arabian Sea coasts of the Sultanate of Oman

Ponnampalam, L. S., Collins, T., Minton, G., Schulz, I., Gray, H., Ormond, R. and Baldwin, R. 2012. Stomach contents of stranded cetaceans along the Sea of Oman and the Arabian Sea coasts of the Sultanate of Oman. Journal of the Marine Biological Association of the United Kingdom 92(8): 1699 – 1710. doi: 10.1017/S0025315411002104.

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ABSTRACT

This study examined the stomach contents of 11 bottlenose dolphins (Tursiops sp.), five Indo-Pacific humpback dolphins (Sousa chinensis) and two spinner dolphins (Stenella longirostris) that were found stranded along the Omani coastline. Across the three species examined, a total of 4796 fish otoliths and 214 cephalopod beaks were found, representing at least 33 species in 22 families. Prey item importance was calculated using the percentage by number and percentage by frequency of occurrence methods, and a modified index of relative importance. The fish families Apogonidae, Carangidae and Scombridae were the most numerically important prey of the bottlenose dolphins. Sciaenidae was the most numerically important fish family for the Indo-Pacific humpback dolphins. The myctophid Benthosema pterotum formed the majority of the prey items of spinner dolphins. Cephalopod remains found in the stomach samples were represented by the families Sepiidae, Loliginidae and Onychoteuthidae. The known depth distribution of prey items of bottlenose dolphins indicated that the animals fed in a wide variety of habitats. Indo-Pacific humpback dolphin prey items indicated feeding in shallow coastal areas. Spinner dolphins appear to have exploited the upper 200 m of the water column for food, where their vertically migrating mesopelagic prey are found at night. Most prey species found in the stomach contents do not appear to be of current commercial importance in Oman. However, the findings here indicated that all three species of dolphins were feeding in areas where artisanal and/or commercial fishing occurs and has conservation implications.