Fraser River sockeye salmon face trio of challenges: study
By Larry Pynn, Vancouver SunMay 22, 2012
Increased numbers of pink salmon, warming ocean temperatures, and salmon farms along migration routes could together be contributing to the long-term decline of Fraser River sockeye, scientists report.
Brendan Connors, a post-doctoral fellow in the school of resource and environmental management at Simon Fraser University, said those three factors, when considered in combination, "appear to play a very important role."
In a paper published in the journal Conservation Letters, researchers said that increasing numbers of pink salmon across the north Pacific Ocean represent increased competition for food with Fraser sockeye.
Connors, lead author on the study, said Russian pink runs are substantial in the north Pacific, estimated at 450 million in 2009. That same year only 1.5 million sockeye returned to the Fraser River, the lowest in more than 50 years.
When Russia's pink runs dropped to 160 million in 2010, 28 million sockeye returned to the Fraser River, the largest run since 1913.
Russia's pink salmon are primarily wild fish, rather than from hatcheries. "Their high abundance is likely a reflection of favourable ocean conditions at northern latitudes," said Connors.
The study said sockeye passing close to salmon farms early in the ocean phase of their life cycle may pick up viruses, bacteria or parasites that reduce their ability to compete with pink.
Increasing ocean temperatures can also reduce survival of juvenile sockeye, the study said, noting the importance of international cooperation on salmon management.
lpynn@vancouversun.com© Copyright (c) The Vancouver Sun
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