Diversity, abundance and size structure of pelagic sharks caught in tuna longline survey in the Indian seas
Diversity and abundance of pelagic shark bycatch in the tuna longline operations in northern Indian Ocean were examined for the period 2004-2010. During the survey 1.2 million hooks were deployed in three regions of seas around India resulting in the catch of 1501 numbers of sharks. Significant variations in the diversity and abundance of pelagic sharks were observed among the three regions of Indian seas. Catches of sharks are prominent in Andaman & Nicobar region contributing 35.15% of the catch by number and 51.46% by weight. In the eastern Arabian Sea, sharks constituted 15.49% and 14.89% of the total catch by number and weight respectively. In western Bay of Bengal, this group contributed 7.74% (by number) and 9.33% (by weight) to the total catch. Alopias pelagicus, Carcharhinus limbatus, Alopias superciliosus and Carcharhinus falciformis were the dominant species of pelagic sharks observed in the Indian seas. Time series analysis of hooking rates revealed drastic decline in the abundance of pelagic sharks in the Arabian Sea as well as Bay of Bengal.