Pelagic megafauna bycatch in the tuna longline fisheries off India

To assess the diversity and abundance of pelagic megafauna caught in the tuna longline survey in the seas around India, data was collected and analysed from survey voyages of four research longliners of the Fishery Survey of India (FSI) during 2004-2010. Study was conducted by operating 11.99 million hooks in three regions of seas around India, i.e., eastern Arabian Sea, western Bay of Bengal and Andaman and Nicobar waters. Significant variations in the diversity and abundance of large pelagics were observed among the three regions of the study area. Besides the target species (yellowfin tuna, Thunnus albacares), 60 species of large pelagics and sea turtles were incidentally caught. Indo-Pacific sailfish, Istiophorus platypterus, was the main bycatch species. In the order of abundance, pelagic stingray (Pteroplatytrygon violacea), common dolphinfish (Coryphaena hippurus), pelagic thresher (Alopias pelagicus), skipjack tuna (Katsuwonus pelamis), and long snouted lancetfish (Alepisaurus ferox), were the other important species recorded. Of the three species of sea turtles caught, olive ridley, Lepidochelys olivacea was prominent. Sea birds and cetaceans were not represented in the longline bycatch of seas around India. Length-weight relationship of 34 species and spatial distribution of seven species are presented and discussed. This study provides information on the relative abundance, size structure and sex ratio of the pelagic megafauna of the seas around India which should be useful for identifying management measures for these ecologically and economically important resources.