National Geographic : 2003 Jul
DEEP TRADITIONS Irishmen have been chasing salmon since mythic hero Finn MacCool ate the Salmon of Knowl edge from the River Boyne and gained eternal wisdom. Salmon fever afflicts Irish anglers from all walks of life, from Ballina townsmen (above) who pay $40 a year to fish the Moy River, to jet-setting consultant Sam Hay (right, at center), who each year pays $3,000 for a week's fish ing at Amhuinnsuidhe Castle, a retreat in Scotland's Outer Hebrides. "These fish are the epit ome of the wilderness and the sea," says Hay, toasting guide Kenny Morrison, far right. salmon aquaculture production in the hands of six multinational companies. The globalization of salmon aquaculture, cou pled with serious environmental concerns, has led to growing opposition and calls for reform. A major scourge is sea lice, which can kill fish by grazing on their flesh. In Ireland, Scotland, and Norway studies indicate that sea lice out breaks at fish farms can have devastating effects on wild salmon and sea trout, a related species. In western Scotland, where aquaculture is located because of sheltered lochs, wild salmon populations have declined far more dramatically than on the east coast, which has only one fish farm. Similar trends have been found in Ireland. In Norway one study showed that 86 percent of the young salmon migrating out of Sognefjorden -which has many fish farms near its mouth were covered with lethal levels of lice. Aquaculture companies are now working to solve the sea lice problem. But what really causes scientists to lose sleep is the continuing escape of massive numbers of farmed salmon. From the earliest years of aquaculture, salmon have escaped whenever seals chewed through pens in search of an easy meal, storms demolished 118 NATIONAL GEOGRAPHIC * JULY 2003 cages, or fish were spilled during handling. But now, with 300 million farmed salmon being sold every year, the magnitude of the escape problem is enormous. Ten to 35 percent of the salmon on the spawning grounds of Norwegian rivers are farmed salmon. In Scotland nearly 300,000 farmed fish escaped last year alone. Detailed studies by Norwegian scientists have shown that wild and farmed fish interbreed. The concern is that a hybrid fish, poorly adapted to life in the wild, will one day spread across the Atlantic. Studies have also found that farmed salmon do not reproduce in the wild nearly as well as native salmon-a phenomenon that, over time, could depress populations. In addition, individual strains of wild salmon have, over thousands of years, adapted to unique conditions in each of 2,600 Atlantic rivers. A genetically homogenous salmon, descended from aquacul ture fish, could be ill suited to life in many rivers and could also leave the species less able to cope with threats such as disease and climate change. "The prospect of losing this genetic variabil ity forever is really frightening," says Torbjorn Forseth, aquatic research director at the Nor wegian Institute for Nature Research.