The following is from the environmental themed advice column EarthTalk®, by the Editors of the non-profit publication E/The Environmental Magazine, that well be regularly featuring here on CLs Green Community.
Dear EarthTalk: Why did 34 million wild sockeye salmon return to the Fraser River in British Columbia this year? The run had been declining for 20 years before now. — David B., Seattle, WA
The miraculous sockeye salmon run in western Canadas Fraser River watershed in the summer and fall of 2010indeed the biggest run in 97 yearsstill has fishers, researchers and fishery managers baffled. Just a year earlier only one million fish returned to spawn. No one seems to be able to say for sure what caused the massive 2010 run, but most agree that it probably had to do with the very favorable water conditions that were present in 2008 when the sockeyes were juveniles. Theyre very vulnerable at that stage of their life, reports John Reynolds, a salmon conservation expert at Canadas Simon Fraser University.
Roberta Hamme, a researcher with Canadas University of Victoria, suggests in a recent study published in Geophysical Research Letters that the ash fall from the eruption of Alaskas Kasatochi volcano in 2008 may be one reason for the huge 2010 run. Iron in the ash, which was spewed far and wide by the erupting volcano and then dispersed further by turbulent weather, served as a fertilizer throughout the North Pacific. The result was huge algae blooms that dramatically improved the fishs food supply. A similar large Fraser River salmon run in 1958 was likewise preceded by a huge volcanic eruption in Alaska.
What was particularly striking about 2010s mammoth run was the contrast against 2009, when the Fraser River sockeye run was a disaster by all accounts. It capped 20 years of decline and was so much worse than anyone had expected that the Canadian government formed a commission to investigate possible causes, reported Daniel Jack Chasan on the Pacific Northwest news website, Crosscut.