Vol. 5, No. 1 Contents
Headline Back Issues
Winter 2000
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The Bay of Fundy debates future of its disappearing salmon cont'd...
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Tracking the salmon
Beginning this spring, the ASF and DFO will expand on a 1999 pilot study that tracked smolts migrating out of their birth rivers into the inner Bay of Fundy. The study combined acoustic tags called pingers, because of the sound they emit, with automated receivers suspended from surface buoys that signaled when the fish passed through the area. The technology allowed scientists to monitor the fish for up to three months, during which time the vast majority of salmon survived the journey from the river to beyond the coastal zone. Consequently, says Dr. Gilles Lacroix, the principal investigator of the smolt tracking study, "It appears that whatever is happening to the salmon is happening farther out at sea." Scientists will now expand the area of study to include the outer Bay of Fundy, and eventually, the Gulf of Maine. Along with transmitters, the researchers will also employ special trawling gear to capture live salmon for examination and release. It is hoped that capturing live salmon will provide key information on growth, disease and parasites, genetic origin and environmental impact. By tracking the migration of fish farther south scientists will also be able to determine how close the wild salmon come to fish farms. "If salmon migrated to feeding habitat in the Fundy Isles area," Lacroix says, "we would then need to look at possible aquaculture interactions." Ocean predators?Because salmon at sea tolerate colder waters, some experts believe that the rise in sea-surface temperatures in the North Atlantic may be the primary driver of the decline. Other possibilities include salmon predators like gray seals, which have increased in recent years.
Sounding like Sherlock Holmes, he adds, "So the question becomes, why did this salmon run build back so easily then, and why now, with no local commercial or sports fishery around, is there such a limited run?" Dadswell says the crash of the wild salmon cannot be attributed solely to natural causes or, as some believe, to some ecological black hole. For years he has pursued a theory that has won him few supporters: that the wild Atlantic salmon are being decimated by illegal drift gill net fleets operating in the waters off southern Greenland, and east of the Faeroe Islands where European salmon feed. "I think the simplest explanation is that adults are being exploited while at sea," he says. In 1992, the United Nations declared a moratorium on large-scale drift net fishing on the high seas. Often referred to as "walls of death," the transparent nets, which can span for miles, ensnare everything in their path including whales, dolphins and turtles. Since then, a number of countries fishing mainly in the South Pacific and the Mediterranean have been found in violation of the resolution. Environmental groups have long argued that the practice is more widespread than is reported. Because of the expense of retrieving satellite records and other classified information that might show evidence of stationary vessels over oceanic salmon feeding grounds, Dadswell and two graduate students are reviewing a range of data including fish landing records by country that might show disparities in Atlantic salmon catches. One record shows that the catch of wild salmon in Baltic Sea countries has nearly doubled since the mid-80s, "while stocks everywhere else are collapsing," he says. He hopes to complete his study by the summer. Dadswell says he has tried for years to persuade government scientists to explore the possibility of rogue drift net fleets, but the response has been lukewarm. "People say it's impossible because it's illegal," he says. "And I say, 'yes, but so is cocaine.'" With 40 years of salmon fishing under his belt, he often cautions fisheries officials, not to "throw solutions at an unknown problem." Still, he adds, when it comes to solving the mystery of the missing fish, "It would be a shame not to pursue it until the very end." |
While pollution, dams and agricultural run-off have degraded many spawning rivers in the Bay of Fundy, scientists say that overall there still appears to be enough stable freshwater habitat to produce reasonable numbers of fish. But once salmon migrating from these rivers hit the ocean, fewer and fewer salmon survivors' return to reproduce. While most of the studies have focused on salmon survival in freshwater, recent advances in technology used to track the fish may provide clues to what happens to them once they leave the rivers. 
Dr. Mike Dadswell, a biologist at Acadia University, has a theory of his own. As a young biologist during the 1960s, Dadswell conducted work on the Alma River in New Brunswick to restore salmon runs. For decades a logging dam had blocked the river at the head of tide, preventing salmon from swimming upstream to spawn. A small commercial fishery operated in the Bay of Fundy at the river's mouth and sports fishing was allowed. In 1964, the dam collapsed and within a couple of years, the salmon returned. "I can remember seeing excesses of 1,000 adult salmon," Dadswell says.