Trawl fishing surviving through sale of previously discarded fish

 Fishermen barely eking out a profit because of overfishing of their target stock, shrimp, are now surviving by selling their bycatch (the low-value fish also caught in the large, indiscriminate nets). Although good for the fishermen, scientists warn that the prolonged trawl fishing along certain areas will lead to an ‘ecological catastrophe’ and the ‘permanent loss of livelihoods for fishers’ as well as other individuals who work in the industry.

A paper published in the current issue of the journal Conservation Letters by researchers from the University of Cambridge shows that the drivers for the use of this once discarded resource are twofold: declining shrimp stocks and profits, and the development of alternative markets, which include the rapidly growing poultry-feed industry.

Trawl fishing is a technique employed the world over in which a fishing vessel drags a gaping net along the ocean floor. Unfortunately, though trawlers target a limited number of species such as shrimp and some fish, trawl nets capture anything in their path and seriously damage the seafloor as well. It's been estimated that trawlers in the tropics capture an average of 10 kilos of bycatch for every kilo of shrimp.

When trawl fishing first began in South and Southeast Asia, trawlers discarded large quantities of bycatch. The lead author of the study, Aaron Savio Lobo from the Department of Zoology, says this is now changing, "Recently there has been a shift in this trend and an increase in the use of the previously discarded bycatch."

Several species of bycatch which were traditionally discarded are now being sold for local consumption. Additionally, there has been increased demand for 'trash fish' to feed the region's rapidly growing poultry industry, a consequence of the country's rising affluence.

The Cambridge team's research demonstrates that even though the profits obtained from the original target catch have fallen almost to nothing, the development of new markets for bycatch now means that trawlers can continue fishing and still remain profitable.

Looking to the policy implications of the study, Lobo says: "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."