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Report: Commercial Fleets Killing Off Giant Fish

Sophisticated fishing fleets are wiping out the world's most famous trophy fish, according to a report in this week's issue of the journal Nature. The study says fishermen have taken more than 90 percent of the biggest predatory fish out of the world's oceans since the 1950s. If present trends continue, the study warns that fish like marlin and swordfish may become extinct in the near future. NPR's John Nielsen reports.

In The Old Man and the Sea, Ernest Hemingway wrote of what it's like to be in a tiny boat, hunting for the ocean's monster fish:

He saw him first as a dark shadow that took so long to pass under the boat that he could not believe its length.  "No," he said. "He can't be that big." 

But he was that big....

Those who want to live that scene had better hurry up, says biologist Ransom Myers of Dalhousie University in Halifax, Nova Scotia. Myers and a colleague spent the last 10 years sorting through a mountain of global fishing statistics to find out whether predatory fish like tuna, swordfish, marlin, cod and halibut were significantly bigger and more numerous before the fishermen arrived.

He found tuna used to be twice as big, and marlins were once on the same scale as killer whales.

Big fish have always been the first to go when commercial fishing boats arrive. Myers says 90 percent of these giants are caught in the first 15 years of commercial fishing in any given area. That was the fate of giant swordfish in the western Atlantic, and the giant bluefin tuna off the coast of Brazil.

Myers says this type of fishing has become a threat to the survival of entire species, and not just the biggest ones. The loss of the giants puts the smaller fish at risk by allowing other species to move in and crowd the little fish out of existence. Fisheries recover very slowly from this change, if they recover at all. Problems are compounded by the long-line fleets that catch fish they weren't even looking for on the millions of hooks they pull behind them.

Myers says there's only one solution: "We've got to cut fishing by 50 percent, and if it's not done we're going to lose the pelagic species."

Environmental groups endorse that plan. Fishermen and government scientists think it's completely unrealistic. Mike Sissenwine, director of science programs at the National Oceanic and Atmospheric Administration, says it's not a viable option -- fish-related businesses around the world would be ruined.

John Sackton, president of Seafood.com, adds that Myers hasn't proved that the loss of the giants leads to a species' imminent extinction. He says the key to keeping fisheries stable is making sure the fish get a chance to reproduce before they are caught, which happens long before the fish are giants.

NOAA's latest survey of American fisheries seems to support this notion, reporting a broad recovery in the nations' fish stocks. But Myers stands by his findings. He says he got the same response when he warned Canadian fishermen that cod stocks in the George Bank were about to collapse. Those fish are now on the Canadian endangered species list.

Copyright 2022 NPR. To see more, visit https://www.npr.org.

John Nielsen
John Nielsen covers environmental issues for NPR. His reports air regularly on NPR's award-winning news magazines, All Things Considered, Morning Edition and Weekend Edition. He also prepares documentaries for the NPR/National Geographic Radio Expeditions series, which is heard regularly on Morning Edition. Nielsen also occasionally serves as the substitute host for several NPR News programs.