Impacts of large pelagic fisheries on the survival of sea turtles in Sri Lanka

Large pelagic fisheries in Sri Lanka are developing rapidly, with an ever-increasing offshore fishing fleet. Over 3000 boats at present are actively engaged in fisheries employing gillnets and longlines accounting for more than 95 % of the total fishing effort. However, both fishing methods have long been cited as major cause for sea turtle mortality. Incidental catch data of sea turtles are somewhat ambiguous to make up a noteworthy representation in the large pelagic catch statistics of Sri Lanka which is collected through port sampling programme. Since all species of sea turtles are protected by law, the turtle encountered in the gear is usually returned to the sea as discards. In complying with the IOTC Resolution 12/04 the conservation of marine turtles, the interaction of sea turtles with fishing gear (separately for gillnet and longline) targeting tuna have been studied at two major landing centers in the west coast; Negombo and Beruwala over one year period via direct communication with fishermen, monitoring of catches, onboard observer programme and stranding data. Between the two fisheries gillnet fisheries have a low sea turtle interaction relative to the longline but relatively higher numbers are reported dead in gillnet fisheries than in longline. Catch and fleet data was used to estimate total number of captures per year at local scale and then at large through a conservative approach. The species of sea turtles recorded in the incidental catch, in order of abundance, were Olive Ridley (Lepidochelys olivacea), and Green (Chelonia mydas). Number of strategies and measures that can be applied to minimize interactions with sea turtles through modifications to gear and/or current fishing practices while curtailing the impact on the catch rates of the targets species have been discussed. It is highlighted that night fishing with either method would noticeably reduce sea turtle interaction with fishing gear.