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also MSNBC website, 28 Jul 05 Big fish halved by overfishing, study says Researchers find five healthy hotspots around the Earth by Associated Press PlanetArk website, 27 Jul 05 Fish Study Shows Decline in Tuna, 'Game' Fish WASHINGTON - Tuna, swordfish and other species favored by fishing fleets gather in "hotspots" across the world's oceans -- but these are in serious decline, according to a survey published on Thursday. The hotspots -- off the east coasts of the United States, Australia, and Sri Lanka; south of Hawaii; and in the southeastern Pacific -- seem to be linked to a type of zooplankton, the researchers found to their surprise. Writing in the journal Science, they said overfishing had clearly caused the biggest declines in both numbers and diversity, although climate change also apparently played a role. Boris Worm of Dalhousie University in Halifax, Nova Scotia, and colleagues studied data from Japanese fishing fleets. "It is like solving a giant puzzle and seeing the night sky in constellations for the first time -- even as the stars are blinking out. It's beautiful and tragic at the same time," Worm said in a statement. The researchers studied data going back 50 years from Japanese longline fisheries, as well as data from the United States and Australia. Longlines are the most widely used fishing gear in the open ocean, with baited lines up to 60 miles (100 km) long that target tuna or billfish but catch many other species too. Not only are the numbers of fish shrinking, but the variety of species is as well, they found. "Diversity declined between 10 percent and 50 percent in all oceans, a trend that coincided with increased fishing pressure, superimposed on strong El Nino Southern Oscillation- driven variability across the Pacific," they wrote. "Everywhere you go, in every ocean basin, our "hotspots" today are only relics of what was once there," Worm said in a statement. "It really hurts to see this." The loss of diversity means that where 10 different species might be found in an area, now just five can be caught. The more diverse an ecosystem, in general, the more it thrives, researchers have found. "It's not yet extinction -- it's local fishing-out of species," added Ransom Myers, also of Dalhousie University. "Where you once had a range of a species in dense numbers, now you might catch one or two of a certain species." The fish gather in the same spots as a type of zooplankton called foraminifera -- single-celled animals that float in the seas and are eaten by a range of animals. "Our paper suggests there is a solution -- while some hotspots have already disappeared, there are still some very special places where species concentrate," Worm said. "We have the chance and the political measures to protect some of these areas. To me, it's the most important thing in the world right now -- to keep as many pieces of the puzzle as we can before we destroy it." MSNBC website, 28 Jul 05 Big fish halved by overfishing, study says Researchers find five healthy hotspots around the Earth by Associated Press WASHINGTON - Scientists say the variety of tuna, marlin, swordfish and other big ocean predators has declined up to 50 percent over the past half-century due to overfishing. For the first time, ecologists and oceanographers mapped the hotspots with the largest concentrations of many big fish species, then and now. Their findings are reported in Thursday's online edition of the journal Science. Researchers who had previously reported an overall decline in the abundance of big fish now say there has also been a significant drop in the number of different types of fish such as tuna and billfish being found in many areas. They did find a few places where fish remain abundant. "We found five large hotspots that are still remaining today, and two of those are in U.S. waters," said Boris Worm, a marine ecologist at Dalhousie University in Canada, the lead author. Those two are in the Atlantic Ocean, east of Florida, and in the Pacific Ocean, south of Hawaii. Two of the other areas are in the South Pacific, east of Australia"s Great Barrier Reef and north of Easter Island. The other is in the Indian Ocean, east of Sri Lanka. The scientists examined the only global data set for big fish species since largescale fishing fleets began spreading globally just after World War II. It is based on Japanese fishing between 1952 and 1999 with the most widespread type of fishing gear, longlines, that are used in the open ocean. Those float for up to 70 miles on the water"s surface, with baited hooks reaching down to 1,000 feet below. Based on that data, the scientists found average declines of about 50 percent in diversity in the Atlantic and Indian oceans, and an average decline of about 25 percent in the Pacific. They also discovered that the sea surface temperature and level of oxygen in the water correlate with where the big fish concentrate. "The peak in big fish diversity is at middle temperatures," said co-author Ransom Myers, a fisheries scientist also at Dalhousie. "Ocean animals don"t like it too hot, or too cold, they like it just right" " at about 77 degrees Fahrenheit. That contrasts with the general distribution of species on land, which is richest in diversity at the equator and wanes toward the poles. Nathan Mantua, a climate scientist at the University of Washington in Seattle who was not part of the research group, said the study is useful for identifying the combined effects of climate variations and fishing on the distribution of the ocean"s largest predator fish. "They highlight that there are biodiversity hotspots that are tied directly to physical structure in the ocean," which includes temperature, dissolved oxygen and currents, he said. "Out in the ocean, it"s pretty clear that the primary cause of the long-term declines in biodiversity is fishing." They also found that concentrations of many big fish lined up closely with the only other known global mapping of ocean life--that of single-celled zooplankton. Steven D'Hondt, a University of Rhode Island oceanographer and a co-author of that 1999 mapping, said "the smallest animals in the ocean and some of the largest show the same pattern of diversity at the global scale." Callum Roberts, a marine conservation biologist at Britain"s University of York, said the study could help policymakers and conservationists determine where best to locate marine-protected areas on the high seas, an issue being debated by the United Nations. "While some hotspots have disappeared, there are still some very special places where species concentrate," said Myers. Two years ago, he and Worm used the same data to show that commercial fishing had depleted the world's oceans of 90 percent of the overall abundance of big fish that flourished 50 years ago. The research was funded by the Sloan Foundation, German Research Council, Pew Charitable Trust and the Natural Sciences and Engineering Council of Canada. links see also Large fish 'may follow dinosaurs' By Jonathan Amos BBC News website, 14 May 05 Global issues: biodiversity loss biodiversity loss, extinction threats, commercial applications of biodiversity |
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