Now a new study suggests that commercial fishing boats may adding to this number. As Alister Doyle reports for Reuters, fishing operations may be wasting up to 10 percent of the fish in their nets right after they were caught—enough to fill 4,500 Olympic-sized swimming pools each year.
The study, published this week in the journal Fish and Fisheries, compiles 60 years of data on industrial fishing practices. The results suggest that the fleets toss back roughly 10 million tons of the 100 million tons of fish they catch each year. As Doyle reports, this happens for a range of reasons, including the fact that the fish are too small, diseased, or not the target species. Russian trawlers, for example, often collect roe from pollock and then dispose of the fish. While some species including sharks, rays and crustaceans can survive being tossed back into the ocean, the process is fatal for most fish species.
“[It’s an] enormous waste ... especially at a time when wild capture fisheries are under global strain amidst growing demands for food security and human nutritional health,” the researchers write in the study.
This number has risen in recent years, George Dvorsky reports for Gizmodo. In the 1950s, fishing fleets wasted about 5 million tons of fish per year. But that number jumped to 18 million tons in the 1980s before dropping down to 10 million tons in the last decade. The latest drop could be the result of better fisheries management and technology, but the researchers believe it may just be a reflection of the dismal state of the ocean: “Discards are now declining because we have already fished these species down so much that fishing operations are catching less and less each year, and therefore there’s less for them to throw away,” Dirk Zeller, lead author of the study and senior research partner with the Sea Around Us, an initiative at the University of British Columbia, says in a press release.
While it is not possible to market all fish caught (obviously diseased fish cannot be sold), that’s not the primary reason for tossing them overboard. “Discards also happen because of a nasty practice known as high-grading where fishers continue fishing even after they’ve caught fish that they can sell,” Zeller tells Carl Engelking at Discover. “If they catch bigger fish, they throw away the smaller ones; they usually can’t keep both loads because they run out of freezer space or go over their quota.”
As Engelking reports, 85 percent of the world’s fisheries are being pushed past their biological limit. While some nations have banned bottom trawling, a method which drags up many unwanted species leading to waste, and some have regulated discards. But, he notes, once boats are in international waters, they are often beyond the limits of enforcement.