Wednesday, April 14, 2010

High Prespawn Mortality in Fraser Sockeye Attributed to Warmer Water

Over the last 10-15 years prespawn mortality in some components of the Fraser Sockeye run has been startlingly high. In some years upwards of 90% of sockeye have died before reaching their spawning grounds. Excellent work done by UBC's Scott Hinch and graduate students in his lab has revealed that warmer temperatures in the Fraser during the migration period have played a major role in high in river mortality. Even more startling is the fact that rather than migrate later during periods of cooler water, some components of the Fraser run are actually entering the river, increasing the impact of high summer temperatures. Sockeye which have historically spent time staging at the mouth of the Fraser during late summer now are entering the river instead. Hinch's group and others have uncovered physiological evidence that sockeye are arriving at the river more reproductively mature, with immune systems, and physiological states which are far more advanced towards spawning than one would expect in fish which should be waiting nearly a month to spawn. Why exactly the salmon have experienced such a shift in physiological condition is unclear but hypotheses range from climate change to disease.

Environmental change and its impacts on salmon populations are out of our hands to some degree, however what is particularly frustrating is DFOs willingness to subject Fraser Sockeye to unknown and potentially disastrous threats of salmon farming when the future of this great run of salmon already hangs in the balance.

More info in an article from the globe and mail...

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