[MARMAM] Cetacean bycatch in Indian Ocean tuna gillnet fisheries

Charles Anderson charles.anderson11 at btinternet.com
Fri Jan 17 10:06:09 PST 2020


Dear Colleagues, 


The following paper has just been published:


Anderson R.C., M. Herrera, A.D. Ilangakoon, K.M. Koya, M. Moazzam, P.L.
Mustika, D.N. Sutaria (2020)

Cetacean bycatch in Indian Ocean tuna gillnet fisheries. Endangered Species
Research, 41: 39-53


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.


The article is open access and is available at:



It is normal for authors, when announcing a new paper, to say how pleased or
delighted they are. Not in this case. 


Charles Anderson

Maldives & UK 

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