Populations of large ocean fish decimated.

Industrial fleets have fished out at least 90 percent of all large ocean predators--tuna, marlin, swordfish, sharks, cod, halibut, skates, and flounder--in just the past 50 years, according to a study published in the May 15 issue of Nature. Researchers Ransom Myers and Boris Worm of Dalhousie University, in Canada and the Institute for Marine Science in Germany discovered industrialized fishing has "scoured the global ocean, leaving no blue frontier" left. In fact, according to their study, human impact on global ocean ecosystems has been vastly underestimated.

"We're so good at killing things," says lead researcher Ransom Myers, "that we don't even know how much we've lost." Declines over the last half century, he says, have been enormous, taking place before we even had data on how large many fish populations might have been.

According to the New York Times, oceanographers not connected with the study say it gives the "best evidence yet that recent fish harvests have been sustained at high levels only because the (fishing) fleets have sought and heavily exploited ever more distant fish populations." When these predators disappeared from the oceans, smaller fish were able to rebound their populations, but only for a short time before they, too, became overfished. Myers and Worm assembled data representing all major fisheries in the world (including large predatory fish communities from four continental shelves and nine oceanic systems). They were surprised to learn that industrial fisheries take only 10 to 15 years to "grind away" any new fish community they encounter to one-tenth of its previous population.

Fishery experts once believed that there were large reservoirs of large fish in open ocean ecosystems and that the sea was a limitless source of food. But data from research trawlers (ships that literally scrape the bottom of the ocean), surveys, and Japanese ships that use long-lines (fishing gear that catches a wide range of species over vast areas) show that the advance and widespread use of these technologies have been a recipe for disaster for most of the world's large predatory fish. It is those fish that, according to Worm, "we most value" for their economic and ecosystem services. And if the fish disappear, so will the millions of communities and businesses that depend on them for food and income.

In a report released in June by the National Oceanic and Atmospheric Association of the U.S. Department of Commerce, government scientists reaffirm that U.S. stocks of fish are being overfished and/or fished at too high a rate. According to the Marine Fish Conservation Network, this is the third time in four years that the status of federally managed fish stocks has deteriorated. Reversing this problem, say experts, requires international cooperation.

In 2002 at the World Summit on Sustainable Development, 192 nations signed on to a non-binding agreement to restore fisheries stocks to their maximum sustainable yield by 2015. This will mean creating an ecosystems-based fishery management system--reducing the percentage offish killed each year by reducing quotas, cutting subsidies, reducing bycatch (fish that are thrown away because they are not economically profitable), and creating networks of marine preserves to protect fish stocks.