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Large Fish Populations Imperiled

yellow fin tuna



OAR/NATIONAL UNDERSEA RESEARCH PROGRAM
For weekend fishermen, there are many tall tales about "the big one that got away." New findings published today by the journal Nature indicate that big fish are indeed hard to catch. But disturbingly, the results suggest that's because the world's large fish--tuna, marlin, swordfish, sharks, cod and halibut among them--have been so exploited by industrial fisheries that 90 percent of them have disappeared from the sea.

That industrial fishing has impacted individual species, such as Atlantic cod off the coast of Newfoundland, is undeniable. But Ransom A. Myers of Dalhousie University in Nova Scotia and Boris Worm of the University of Kiel in Germany examined the problem of overfishing globally. They conducted a 10-year-long study that assembled data sets representing all major fisheries in the world over the past 47 years. The analysis included biomass estimates of large predatory fish populations from four continental shelves and nine oceanic systems. The team determined that within the first 15 years of operation, commercial fisheries reduced fish populations by 80 percent on average. In the Gulf of Thailand, for example, 60 percent of large finfish, sharks and skate were lost within the first five years of commercial trawl fishing. "Since 1950," notes Myers, "with the onset of industrialized fisheries, we have rapidly reduced the resource base to less than 10 percent--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."

What is more, the researchers categorize their findings as conservative estimates. For one thing, the catch rate for longline fishing has dropped by a factor of 10 over a span of 10 years despite significant technological improvements. In order to stem the tide of devastation, the authors suggest, an overall reduction in the percentage of fish killed each year, perhaps by as much as 60 percent, is necessary. Although simple in theory, putting such guidelines into practice will require global cooperation and a willingness to give up short-term gains in exchange for long-term prosperity. But to ignore the problem, Myers says, could be disastrous. "If present fishing levels persist," he remarks, "these great fish will go the way of the dinosaurs."

"The World's Imperiled Fish," by Carl Safina (Scientific American Presents, Fall 1998), is available for purchase at Scientific American Digital.
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