Tuna fishing bane for turtles
doi:10.1038/nindia.2010.71 Published online 31 May 2010
The charismatic sea turtles of the Indian seas face a significant threat due to unscientific tuna longline fishing, according to a new study by the Fishery Survey of India.
The study conducted between 2005 and 2008 by four longline vessels of the survey body has revealed that 87 turtles were hooked or entangled in the longlines. Of these, 79 were vulnerable olive ridleys, 6 endangered green turtles and two critically endangered hawksbills.
The tuna longline fisheries survey in the Indian exclusive economic zone (EEZ) also showed that the turtles were most vulnerable along India's east coast (the Bay of Bengal region) followed by the west coast (Arabian Sea). However, in the Andaman and Nicobar waters, instances of sea turtles getting entangled in the tuna longlines were meagre.
"Considerable effort has been made to reduce turtle bycatch in trawl fisheries with turtle excluder devices (TEDs). But relatively little attention has been focused on the impact of longline fisheries on turtles," says Sijo P. Varghese of the Fishery Survey of India. He conducted the study with colleagues S. Varghese and V. S. Somvanshi.
Turtle bycatch in commercial fisheries has been identified as a major source of incidental mortality for large juveniles and adult sea turtles. For instance, the Orissa olive ridley population — one of the three mass nesting rookeries worldwide for this species — has been adversely impacted by coastal trawl and fill net fisheries.
"In India, the threat for sea turtles from longlines has received little attention, except for some preliminary studies," Varghese says. This survey provides quantitative data on the magnitude of sea turtle incidental catch of tuna longline fishery in the Indian EEZ.
- Varghese, S. P. et al. Impact of tuna longline fishery on the sea turtles of Indian seas. Curr. Sci. 98, 1378-1384 (2010)