Missing salmon spawn political battle

 作者:戈嫂     |      日期:2019-03-01 01:16:16
By DEBORA MACKENZIE THREE million sockeye salmon, a third of the world’s biggest population of the fish failed to show up at their breeding grounds on Canada’s west coast this year. While a fierce political battle has broken out between the US, Canada and Indian tribes over who is to blame, scientists suspect one of the culprits may be El Nin˜o, the reversal of winds and currents in the Pacific Ocean that usually happens every four to five years. For the first time on record, El Nin˜o has returned for a fourth consecutive year. Sockeye, sold in tins as “red salmon” in Europe, is the most prized of the six Pacific salmon species. Each year, half the world’s sockeye head for the huge Fraser River system in British Columbia to spawn. Before the fish enter the river, many are caught by Canadian and American fishermen off Vancouver Island. Farther up the river are some twenty fisheries operated by different Indian groups. The fish are counted at the river mouth well before they reach the native fisheries. As they enter the estuary, the sockeye encounter four acoustic beams. When a fish breaks the beam, its passing is automatically recorded. This year scientists counted 10 million fish at this point. When the salmon reach the spawning grounds, after running the gauntlet of the Indian fisheries, they are counted again. This year, allowing for the numbers the Indians reported catching, there were 3 million fewer than expected. Such a large dent in the breeding stock poses a serious threat to the future of the sockeye fishery. With so much at stake, a fierce political battle is now raging, with Canadian and American offshore fishermen blaming each other for overfishing, and both blaming the Indians. The Indians blame the offshore fishermen. Canada has set up a Royal Commission to investigate. But although “it seems likely that there has been a lot of unreported fishing”, the problem might not lie entirely with the fishermen, says Tony Pitcher, head of the Fisheries Centre at the University of British Columbia. The fish count at the mouth of the river could have been wrong. Some fish could have swum across the acoustic beams several times, he says. The counting system is supposed to allow for this, “but we could have got it wrong”, he says. Overcounting might have disguised the fact that fewer fish than expected entered the estuary this year. That is possible, says Pitcher, because this year a system of quotas for American and Canadian fishermen “completely broke down”, leading to a fisheries war from Vancouver to Alaska. Canadian fishermen “were encouraged to go out and catch what they could” to deprive their rivals of salmon. Another possibility is that the fish died in the river. One of the effects of El Nin˜o has been to warm the water in the river. According to Pitcher, water in the Fraser system has been 21 °C, a degree or more higher than normal, for unprecedented lengths of time. Sockeye swimming in such warm water “use up their energy reserves fast, and may die before they reach the spawning grounds upriver”, says Pitcher. “You might think it would be hard not to notice a million dead fish … but it’s a big river system.” There are also plenty of otters, eagles and bears waiting to snap up dying salmon. Peter Larkin, an independent fisheries scientist advising the government of British Columbia, says the missing millions might be accounted for by uncertainties all along the system: errors in counting, and under-reporting of commercial and native catches. “After all,” says Pitcher,