Pesticides in B.C. rivers damaging sense of smell in salmon, study says
Chad Skelton
Vancouver Sun
Saturday, June 14, 2008
Pesticides in B.C.'s rivers may be partly to blame for declining salmon stocks because the chemicals are interfering with the species' delicate sense of smell, according to a new study by researchers at Simon Fraser University.
The ability to smell is vitally important for salmon, for everything from sensing predators in the water to being able to identify the proper stream to return to for spawning.
Scientists have known for some time that pesticides can damage a fish's olfactory system, but most studies looked at the impact of a single chemical in high concentrations.
So researchers at SFU, working with Environment Canada and the Department of Fisheries and Oceans, decided to look at what impact a real-world mix of chemicals would have on the species.
First, they tested the water on a stretch of the Nicomekl River in south Surrey, finding a mixture of several different types of pesticides.
Then, they recreated that mixture in the lab and exposed juvenile rainbow trout -- a salmon species also known as steelhead -- to the polluted water for 96 hours.
To test the sense of smell, they exposed the fish to L-serine -- an amino acid given off by predators, like bears -- then used electrodes that measured activity in the fish's olfactory neurons.
What they found is that the mixture led to a 20-per-cent decline in the fish's sense of smell.
"The bottom line is that, looking at concentrations similar to that in the river, they could not smell as well," said Keith Tierney, lead author of the study.
Tierney, who is now at the University of Windsor, said it's hard to know what impact such a decline might have on fish behaviour -- for example, whether it's enough to impact salmon's ability to find their home stream -- but he said it's definitely cause for concern.
"It alters something that's critically important to their life," he said. "They use it to differentiate their siblings from predators, for smelling food, for imprinting to their stream, for returning to that stream."
Tierney said he's now working on trying to determine exactly what impact pesticide concentrations are having on salmon behaviour.
But he said he's confident it's having some kind of negative impact.
"I would say, unequivocally, it's part of the problem. Pesticides are definitely affecting their behaviour," he said. "I don't think it's the whole reason why salmon are having problems right now. But it certainly looks like it's part of the reason."
Tierney's study appeared in this month's issue of the journal Environmental Science & Technology.
cskelton@png.canwest.com© The Vancouver Sun 2008
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