Bottom trawlers toss tons of fish overboard

Researchers at the University of British Columbia say fisheries worldwide engaged in bottom trawling have tossed 437 million tons of seafood worth $560 billion overboard over the past 65 years.

The study, published in mid-May in the journal Fisheries Research, documents the growth in bottom trawling, in which fish not targeted are caught up in huge nets dragged along the seabed.

“Industrial fisheries do not bring everything they catch to port” said Tim Cashion, lead author of the study. “During the period we studied, they threw out over 750 million tons of fish and 60 percent of that waste was due to bottom trawlers along,” said Cashion, a researcher with the Sea Around Us initiative at UBC’s Institute for the Oceans and Fisheries.

Along with fish not targets, bottom trawls snag deep sea corals, sponge beds and more, and unwanted catch is dumped back into the ocean, the study said.

As part of their research, Cashion and his colleagues identified fishing tools used by industrial and artisanal fisheries in each maritime country and territory and paired them with millions of records in the Sea Around Us catch database that include reported and unreported catches by fishing country, fishing sector, year and species.

They found that globally industrial and artisanal fisheries caught 5.6 billion tons of fish over the last 65 years. Nearly 28 percent of that catch was taken by industrial bottom trawlers, which accounted for nearly 60 percent of fisheries discards.


“They threw away fish that, even though are not the most valuable, are perfectly good for human consumption,” said Deng Palomares, co-author of the study and Sea Around Us project manager. “Had they landed that catch, they would have made $560 billion according to our price dataset.”

Conversely, all small-scale fisheries combined were responsible for only 23 percent of the global catch, or about 1.3 billion tons over the past 65 years, but their catch was worth much more because they use small gillnets, traps, lines, hand tools and similar utensils to catch specifically what they want, Palomares said.