Proliferation of Hatchery Fish Eroding Wild Salmon Stocks, Study Says

The release of billions of hatchery-raised salmon is harming wild salmon populations in the north Pacific, according to a new study. The annual release of 5 billion salmon from Alaska and Japan — bred to augment wild salmon populations — has caused a spike in fish populations, nearly doubling the combined population of adult pink salmon, chum salmon, and sockeye salmon since the 1950s, say researchers at Simon Fraser University in Canada. But faced with stiffer competition for food, wild salmon are increasingly returning to spawning grounds underweight and less able to reproduce. Additionally, the interbreeding of hatchery and wild salmon has weakened wild stocks because hatchery fish are not subjected to the same selection pressures as wild fish. “This has been shown to degrade genetic diversity and could make wild salmon less able to cope with variations in natural conditions,” said Randall Peterman, co-author of the study published in Marine and Coastal Fisheries. The authors say the results suggest a need for international regulations for hatchery fish, since salmon released on one side of the Pacific can harm wild stocks on the other.