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Ecological studies and conservation of small cetaceans in the Sultanate of Oman, with special reference to spinner dolphins,

Authors

Ponnampalam, L. S.

Year

2009

Secondary title

University Marine Biological Station, Millport

Pages

347

Keywords

Arabian Sea, diet, dolphin watching, dolphin watching, fisheries, Gulf of Oman, Oman, Spinner dolphin, Stenella longirostris, stomach contents, tourism, tourism, whale watching

Abstract

Small boat surveys were conducted in two main areas in Oman from 2004 to 2006: (1) the Muscat capital area and (2) the Gulf of Masirah. Thirteen cetacean species were sighted during surveys, comprising three species of mysticetes and ten species of odontocetes. Analyses of sightings data relative to bathymetric and environmental variables revealed habitat trends in the five most frequently encountered species. A previously undocumented calving ground for Bryde’s whales was also revealed in the Gulf of Masirah. Spinner dolphins in the Muscat capital area were consistently present nearshore in the mornings, but moved offshore as the day progressed. ‘Resting’ behaviour occurred in the morning, although ‘resting’ probably also occurred during long periods of ‘slow travel’. ‘Feeding’ was confined to the late afternoon, over deeper waters. Stomach contents of bottlenose, Indo-Pacific humpback and spinner dolphins revealed a highly piscivorous diet. Bottlenose dolphin diet comprised prey from a wide variety of habitats. Stomach contents of humpback dolphins concurred with their shallow water, turbid habitats, while stomach contents of spinner dolphins indicated that their movements offshore were to feed on organisms of the mesopelagic layer. Spinner dolphins rested less and ‘milled’ significantly more when boat numbers around them increased. While 82.8% of questionnaire respondents stated that the boat driver maintained a good distance from the dolphins, only 25.4% were aware of legal guidelines. Most respondents felt that legal guidelines should be in use and would have opted to join tours with companies accredited as ‘responsible operators’. Omani fishermen around Muscat said that spinner dolphins were the most frequent cetacean species in bycatch, usually in gillnets. Interviews also revealed that fishermen elsewhere targeted dolphins for shark bait. Scientific research, monitoring and cooperation between scientists, stakeholders and governmental bodies is necessary to ensure proper conservation and management of cetaceans in Oman.
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