Opportunistic observations on the distribution of cetaceans in the Malaysian South China, Sulu and Sulawesi Seas and an updated checklist of marine mammals in Malaysia

ABSTRACT

Opportunistic observations for cetaceans were conducted during the 2009 Prime Scientific Sailing Expedition, onboard the Royal Malaysian Navy Hydrographic vessel, KD PERANTAU. A total of 21 days was spent conducting observations in the Malaysian waters of the South China, Sulu and Sulawesi Seas. The survey yielded a total of 27 sightings and comprised (in order of frequency) the spinner dolphin (Stenella longirostris), bottlenose dolphin (Tursiops sp.), pantropical spotted dolphin (S. attenuata), unidentified dolphins, and an unidentified species of whale. The depth range for spinner dolphins ranged from shallow continental shelf depths to deep waters beyond the shelf. Similarly, bottlenose dolphins were found both in inshore and offshore waters, and based on external morphology, were likely to be T. aduncus. Despite reported high cetacean diversity in neighbouring countries such as the Philippines and Indonesia, the diversity of cetaceans observed during the expedition was low, perhaps owing to seasonal oceanography. Although opportunistic in nature, the survey provided a rare opportunity to study the diversity and distribution of cetaceans in deeper offshore waters that are otherwise difficult to reach by smaller vessels. The results here emphasise the need for further dedicated cetacean research in the pelagic waters of the South China, Sulu and Sulawesi Seas. This paper also uses data from the opportunistic survey and other records collated by the author to construct an updated checklist of marine mammals in Malaysia as a means of providing the most comprehensive overview of confirmed species records in the country and to further assist future research and conservation plans.