Industrial fishing has devastated the marine environment, wiping out 90 per cent of populations among the world's biggest species over the past 50 years, a study published today concludes.
The scale of the loss has astounded fisheries experts, who had thought the open oceans still teemed with "sea monsters" such as giant marlin, tuna and swordfish.
Ransom Myers, a marine biologist from Dalhousie University in Halifax, Nova Scotia, said that industrial fishing took no more than 10 or 15 years to grind any new fish community it encountered to a 10th of its previous size. "From giant blue marlin to mighty bluefin tuna, and from tropical groupers to Antarctic cod, industrial fishing has scoured the global ocean. There is no blue frontier left," Dr Myers said yesterday.
Working with Boris Worm, of the University of Kiel in Germany, Dr Myers investigated four continental shelves and nine open-ocean regions from the time when they were first exploited to the present.
"Since 1950, with the onset of industrialised fisheries, we have rapidly reduced the resource base to less than 10 per cent, not just in some areas, not just for some stocks, but for entire communities of these large fish species from the tropics to the poles," Dr Myers said.
The researchers, whose findings appear in the journal Nature, also gained access to data on the decline of the longline fishing catch by the Japanese fleet. Longline fishing, which uses lines armed with thousands of hooks trailing for many miles, is the most widespread fishing gear and the Japanese fleet's operation is the most extensive, covering all oceans apart from the circumpolar seas. "Whereas longlines used to catch 10 fish per 100 hooks, now they are lucky to catch one," Dr Myers said.
Jeremy Jackson, of the Scripps Institution of Oceanography, said the average size of fish caught today was dwarfed by those routinely landed in the past. "We had oceans full of heroic fish, literally sea monsters. People used to harpoon three-metre-long swordfish in rowboats. Hemingway's Old Man and the Sea was for real," Dr Jackson said.
The most efficient marine predators were on average only a fifth to a half of the size they once were. Dr Myers said: "The few blue marlin today reach one-fifth of the weight they once had. In many cases, the fish caught are under such intense fishing pressure, they never even have the chance to reproduce."
Dr Myers and Dr Worm argue for a cut of at least 50 per cent in the number of fish caught to help to provide sustainable fisheries for the future. "We are in massive denial. We have to understand how close to extinction some of these populations really are. And we must act now," Dr Myers said.Reuse content