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Pesticides Blamed for Plummeting Salmon Stocks

from New Scientist

A weak mix of pesticides in river water dampens a salmon's sense of smell, say researchers. In experiments, Steelhead rainbow trout exposed to low levels of 10 common agricultural pesticides could not perceive changes in levels of a predator's scent.

"You can imagine if a fish is unable to detect just how close it is to a [wading] bear, it's a problem," says Keith Tierney, a toxicologist who led the study while at Simon Fraser University in Burnaby, British Columbia.

A depressed sense of smell might also keep fish from finding mates and food. Trout are closely related to salmon, and, though the theory is unproven, pesticides may be a cause of plummeting salmon stocks in Canada and the US, Tierney says.