Bycatch, low-value fish caught unintentionally by indiscriminatory trawling nets, has traditionally been thrown back into the sea.

But now developing markets for bycatch, coupled with increasingly unprofitable shrimp catches, are threatening to push fisheries to extinction, spelling disaster for marine ecosystems and fishermen, according to research published in the journal Conservation Letters.

Shrimp fishermen in south and southeast Asia are trawling for longer hours and in more areas, said the authors, to boost their dwindling income by selling their bycatch for poultry feed, aquaculture and local consumption.

Shrimp trawling generates more bycatch than any other type of fishery, with up to 10kg of bycatch captured for each kilogram of shrimp.

But the study's authors warn, ‘If appropriate measures are not taken immediately to limit overfishing then the outcomes could be catastrophic for the ecosystem and result in the permanent loss of livelihoods for the fishers in the region.’
 
Environmentalists have campaigned for years about the wastefulness of bycatch but have questioned the viability of prolonged trawling to supply a bycatch market.

‘On the surface, utilising bycatch species is of course a good thing,’ said Willie McKenzie, Oceans Campaigner for Greenpeace. ‘But in reality we should be developing more selective and specific ways of fishing.

‘Commodities like shrimp and salmon have gone, in just a couple of decades, from being luxury food to cheap, undervalued food. It is this cheapness that has been the real driver to find economic value in the bycatch.’

‘While a commercial market for bycatch may make a fishery economically viable,’ said Toby Middleton, UK Country Manager of the Marine Stewardship Council, ‘if that bycatch is based on fundamentally unsustainable fishing practises then that leaves question marks over the long term viability of that fishery, either economically or environmentally.’

Useful links

The study in Conservation Letters

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