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In hot water. . NS 20 Nov 99

After years of overfishing, global warming could decimate Europe's cod

WARMER waters in the Atlantic may be driving the dramatic decline in stocks of cod and other white fish off the coasts of Europe. Even though fishermen have cut their catches by a third in the past two years, young fish especially are still disappearing from a wide area across the northeast Atlantic, scientists wam. "It's been a miserable year right across the northeast Atlantic," says Robin Cook of Scotland's Aberdeen Marine Laboratory. "Even in the Barents Sea north of Scandinavia, cod are in dreadful shape." As a member of the Advisory Committee on Fisheries Management of the International Council for the Exploration of the Sea (ICES), Cook is now calling for even bigger cuts of 40 per cent in the North Sea cod catch. Though fishermen have reduced their catches and the number of mature fish has gone up, Cook says, the numbers of young fish joining the population have been very low in the last two years. British fisheries minister Elliot Morley has already given the ICES scientists his backing. "We don't have a great deal of choice about this," he says. "If we don't make cuts some fish stocks will collapse." Europe's fisheries ministers will consider cuts at a meeting in Brussels next month. The latest crisis is part of a long-term slide in the number of white fish in the North Sea and surrounding areas, triggered in part by overfishing. Until the early 1980s, cod catches in the North Sea averaged around 300 000 tonnes a year but are now just over a third of that. A 40 per cent cut would reduce the catch to 80 000 tonnes in the North Sea, and ICES scientists want to halt fishing altogether in the Irish Sea. "We are not sure what is going on," says Cook. Cuts in catches have done their job. The spawning stock-the number of mature fish producing eggs-is now twice what it was ten years ago. But the number of young fish growing to maturity is still declining. "We don't know why," says Cook. "It may be something as simple as the weather." But he fears that longer-term climate change could be involved. "The cod is a cold-water fish. The North Atlantic is becoming warmer, so it could be that they are retreating north." Less than three years ago Cook said that North Sea cod could collapse unless there was a substantial reduction in the rate of fishing (New Scientist, 8 February 1997, p 6). At the time he argued that cod were on the brink of an irreversible decline, and his wamings helped push European fisheries ministers to lower quotas. But fears are still growing that European waters could be facing the same catastrophe that hit Canadian waters earlier in the decade, when the one of the world's richest cod fisheries, on the Grand Banks, collapsed. Fred Pearce

Extinction point
It only takes one fish with the Trojan gene to invade a population and wipe it out NS 4 Dec 99

A SINGLE genetically modified fish could turn Darwinian evolution upside down and wipe out local populations of the species if released into the wild, biologists warn. They add that other organisms could face the same risk from transgenic relatives. William Muir and Richard Howard of Purdue University in West Lafayette, Indiana, made the discovery while model- ling ecological risks associated with genet- ically modified organisms (GMOs). They have dubbed their idea the "Trojan gene" hypothesis. "This resembles the Trojan horse," says Muir. "It gets into the popula- tion looking like something good and it ends up destroying the population." The researchers studied fish carrying the human growth hormone gene hGH, which increases growth rate and final size. Biolo- gists in the US and Britain are experiment- ing with salmon engineered in a similar way, although no one has yet begun com- mercial production. Muir and Howard included hGH in embryos of a fish called the Japanese medaka (Oryzias latipes), a common aquar- ium fish that is widely used in research. They found that modified individuals became sexually mature faster than normal fish and produced more eggs.

Other experiments using non-modified fish also showed that larger males attracted four times as many mates as their smaller rivals. This effect is also known in salmon. Muir predicts that bigger, engineered fish would enjoy the same advantages. So the hGH gene would quickly spread through a fish population. But Muir and Howard also found that only two-thirds of engineered medaka sur- vived to reproductive age compared with wild medakas. So the spread of the growth hormone gene could make populations dwindle and eventually become extinct. To quantify this, the researchers plugged their results into a computer model to find out what would happen if 60 transgenic individuals joined a wild population of 60 000 fish. The population became extinct within just 40 generations. Even a single transgenic animal could have the same effect, they found, although extinction would take longer. "You have the very strange situation where the least fit individual in the popu- lation is getting all the matings-this is the reverse of Darwin's model," says Muir. "The sexual selection drives the gene into the population and the reduced viability drives the population to extinction." The researchers say their results are the first evidence that GMOs could have cata- strophic consequences on their own species. David Penman, a fish geneticist at the University of Stirling, welcomes the dis- covery. But he says there is evidence that some transgenic fish modified with growth hormone have reduced sperm production and mating success. "If large males tend to mate with large females, this would often result in matings between transgenics," he adds. This would decrease rather than increase the spread of the gene. But John Beringer of Bristol University, a former chairman of the British comn-dttee that advises the government on GMOS, says the research is a warning. "It would make it very difficult for anyone at the moment to approve the release of GM fish carrying growth hormone," he says. "I would have to give a great deal of consideration about whether that's an intelligent route to go down." Muir says that the model may prove an invaluable tool in assessing the dan- gers of GMOS. He hopes to test its pre- dictions in tightly controlled fish farm ponds. Matt Walker

Source: Proceedings of the National Academy of Sciences (vol 96, p 1 3 853)

Lobster trap
Rising catches may hide a population crash NS 25 Dec 99

CATCHES of lobster, a traditional Christmas treat in much of Europe, are soaring. But scientists fear that bumper catches will be followed by a population crash. And efforts to regulate the fishery are being hindered by a 240-year-old treaty. The North American fisheries are an important source of imported lobster for European tables. Fishermen left underemployed by the collapse of other commercial fisheries in North America have been turning their hands to lobster. 'Me number of people working in the industry has doubled since 1980. From an average of 7600 tonnes a year between 1977 and 1986, the average catch in the northeastern US has now grown to 32 000 tonnes. Similar increases have taken place in Canada. Fortunately the population of lobsters has kept pace with the increasing catches. "At first we thought it was because there were fewer young cod to eat the lobster larvae," says Steve Murawski of the National Marine Fisheries Service in Woods Hole, Massachusetts. "But the increase in lobsters started before the major decline in cod." Now, he says, the chief suspect is global warming. Lobsters grow faster in warmer water. Unfortunately, the minimum legal length for lobster destined for the pot is about eight centimetres. Many lobsters grow this big a year before they become sexually mature. So they won't reproduce before they are caught. The fishing boom means few lobster have a chance to grow beyond minimum length. "Three quartan or more of the catch in some places is not yet mature," says Murawski@ "In some places we are leaving only 2 per cent of the potential egg laying females." If conditions for the survival of lobster larvae should become slightly less favourable, the population could crash. And the slow-maturing lobster would take a long time to recover. "We had a similar crash in red king crab in the Bering Sea in the 1980s, and it still hasn't recovered," says Murawsld. One answer would be to increase the minimum legal size, but fishermen object, believing there would be a smaller market for larger, more expensive lobster. Signs of overfishing are already emerging on the southwestern coast of Nova Scotia, where catches in the past couple of years have been down 30 per cent. The Canadian gov ernment has cut the season for catching lobsters to two months a year to try and preserve stocks. But in October, in an unrelated fishing dispute, the Canadian supreme court ruled that under a treaty signed in 1760, the local Mi'kmaq and Maliseet tribes have unhin dered access to the lobster. Native fishermen immediately began setting their traps, two months before the season opened for other fishermen. They retaliated by burning buildings and smashing lobster traps-landing one native boy in hospital. Native leaders have now declared a voluntary moratorium on lobster fishing in the hope that new ways of controlling catches will be devised before the next season opens. Debora MacKenzie

River of no return NS 5 Jun 99

Are gender-bending chemicals stopping salmon from coming home to spawn?

A CHEMICAL that mimics oestrogen may be responsible for the disappearance of North America's Atlantic salmon, whose stocks have plummeted by 90 per cent over the past 20 years despite the efforts of conservationists. Biologists think that 'gender-benders" in sewage and industrial effluent could be harming fish. In March, the European Commission's scientific committee on toxicity said such compounds could pose a threat. The commission wants to study 500 of them to see if they should be banned. The effects of oestrogen mimics have mainly been seen in laboratory studies. However, Wayne Fairchild and colleagues at the Canadian Department of Fisheries and Oceans in Moncton, New Brunswick, have now shown that the number of mature salmon re g to rivers is closely related to the amount of a chemical, 4-nonylphenol, sprayed on them as young fish (Environmental Health Perspectives, vol 107, p 349). Salmon are born in rivers' migrate to sea for one to three years, then return to their native streams to spawn. In various years between 1973 and 1990, areas containing salmon streams in Atlantic Canada were sprayed with an insecticide called aminocarb to kill spruce budworm, a timber pest. One formulation, Matadl l.8D, included 4-nonylphenol as a surfactant. Fairchild's team compared the numbers of adult.salmon retuming to different tributaries of the Restigouche River in New Brunswick in 1977 with the amounts of Matacil spray washing into the streams when those fish were preparing to go to sea. More spray in the rivers resulted in fewer mature salmon coming back in later years. "No one had thought to look two or three years later for an effect of spraying," says Fairchild, "T'he relationship was so close, we thought we'd made a mistake." In years when the area was sprayed with a formulation of aminocarb that did not include 4-nonylphenol, however, there was no correlation between the amount of spray and the number of salmon that later retumed to spawn. When they move to seawater, salmon undergo profound changes, some under the control c of oestrogen. Steffen Madsen at Odense University in Denmark has shown that this process, called smoltification, is impaired in salmon fed or injected with oestrogens, including nonylphenols-and that such smolts are more likely to die when they reach salt water. "The result is intriguing," says Fred Whoriskey, fisheries scientist for the Atlantic Salmon Federation, a conservation group in St Andrews, New Brunswick.

Spraying with 4-nonylphenol has been discontinued in recent years, but Fairchild has evidence that the chemical is still present at similar concentrations from sewage, pulp and textile plant run-off. He believes oestrogens "could be why, even in rivers where they have made real improvements, salmon are still going to sea, and never coming back". Debora MacKenzie