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ESR 41:39-53 (2020)  -  DOI:

Cetacean bycatch in Indian Ocean tuna gillnet fisheries

R. Charles Anderson1,*, Miguel Herrera2, Anoukchika D. Ilangakoon3, K. M. Koya4, M. Moazzam5, Putu L. Mustika6,7, Dipani N. Sutaria7

1Manta Marine, PO Box 2074, Malé, Republic of Maldives
2OPAGAC, C/Ayala 54 2A, 28001 Madrid, Spain
3215 Grandburg Place, Maharagama 10250, Sri Lanka
4Central Marine Fisheries Research Institute, Kochi, Kerala 682018, India
5WWF Pakistan, 46-K PECHS Block 6, Karachi 75400, Pakistan
6Cetacean Sirenian Indonesia, Jl. Kalibaru Timur II/31, Kalibaru, Cilincing, North Jakarta 14110, Indonesia
7College of Science and Technology, James Cook University, Townsville, Queensland 4811, Australia
*Corresponding author:

ABSTRACT: Pelagic gillnet (driftnet) fisheries account for some 34% of Indian Ocean tuna catches. We combined published results from 10 bycatch sampling programmes (1981-2016) in Australia, Sri Lanka, India and Pakistan to estimate bycatch rates for cetaceans across all Indian Ocean tuna gillnet fisheries. Estimated cetacean bycatch peaked at almost 100000 ind. yr-1 during 2004-2006, but has declined by over 15% since then, despite an increase in tuna gillnet fishing effort. These fisheries caught an estimated cumulative total of 4.1 million small cetaceans between 1950 and 2018. These bycatch estimates take little or no account of cetaceans caught by gillnet but not landed, of delayed mortality or sub-lethal impacts on cetaceans (especially whales) that escape from gillnets, of mortality associated with ghost nets, of harpoon catches made from gillnetters, or of mortality from other tuna fisheries. Total cetacean mortality from Indian Ocean tuna fisheries may therefore be substantially higher than estimated here. Declining cetacean bycatch rates suggest that such levels of mortality are not sustainable. Indeed, mean small cetacean abundance may currently be 13% of pre-fishery levels. None of these estimates are precise, but they do demonstrate the likely order of magnitude of the issue. Countries with the largest current gillnet catches of tuna, and thus the ones likely to have the largest cetacean bycatch are (in order): Iran, Indonesia, India, Sri Lanka, Pakistan, Oman, Yemen, UAE and Tanzania. These 9 countries together may account for roughly 96% of all cetacean bycatch from tuna gillnet fisheries across the Indian Ocean.

KEY WORDS: Bycatch · Gillnet · Driftnet · Dolphin

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Cite this article as: Anderson RC, Herrera M, Ilangakoon AD, Koya KM, Moazzam M, Mustika PL, Sutaria DN (2020) Cetacean bycatch in Indian Ocean tuna gillnet fisheries. Endang Species Res 41:39-53.

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