A team of researchers from Canada and the United States has published an article stating that pink, chum and sockeye salmon in the North Pacific are now twice as abundant as in the 1950s.
The article, “Magnitude and Trends in Abundance of Hatchery and Wild Pink Salmon, Chum Salmon, and Sockeye Salmon in the North Pacific Ocean,” reveals that about 718 million adult salmon returned to their spawning grounds in 2005, which is the most recent year that figures were available.
According to the article, the skyrocketing adult salmon population is fueled by the annual release of about five billion juvenile salmon from Japanese and Alaskan hatcheries.
Not only is there concern about overcrowded conditions in the North Pacific, many of the hatchery fish may not be well suited to changes in environmental conditions. The study suggests that increased survival rates were possibly due to few predators or more food in some regions.
The study doesn’t deal with all salmon species, just pink, chum and sockeye. Chinook, steelhead and coho were not a part of the study because estimation of hatchery versus wild returns of these species is more complicated.
The article is available in the peer reviewed online October edition of Marine and Coastal Fisheries: Dynamic Management and Ecosystem Science. It is authored by Gregory T. Ruggerone, Natural Resources Consultants, Inc.; Randall M. Peterman and Brigitte Dorner, School of Resource and Environmental Management, Simon Fraser University, Burnaby, British Columbia; and Katherine W. Myers, School of Aquatic and Fishery Sciences, University of Washington.
What concerns the research team is the growing competition between hatchery salmon and wild salmon.
“Salmon originating from distant regions intermingle in the North Pacific – competing for the food,” explained senior author Ruggerone. “A concern with the hatcheries is that they release a constant and large number of juveniles, no matter what the ocean conditions are. In some years ocean conditions are more favorable for foraging salmon than other years.
“The large number of hatchery fish can lead to suppressed growth of wild stocks – especially in the years when ocean conditions are less favorable to supporting large number of salmon in the ocean. This can be critical for less productive, less abundant wild stocks.”
According to the team’s research, adult hatchery salmon account for at least 20 percent of the total adult salmon production. In Asia, 76 percent of all adult chum salmon from 1990 to 2005 came from salmon hatcheries. Surprisingly, wild chum salmon did not increase in abundance after the ocean regime shift in the mid-1970s, as did sockeye and pink salmon. Instead, hatchery production of chum salmon throughout the North Pacific began to exceed that of wild chum salmon in the early 1980s, leading the authors to suggest that large hatchery production may have suppressed wild salmon growth and survival, including depressed chum salmon stocks in western Alaska.
“Unless international agreements are developed to manage production levels, hatchery fish may dominate the ocean,” warned Peterman who serves as Canada Research Chair in Fisheries Risk Assessment and Management, and is a member of the research team.
“Hatchery fish have not been through the same selective pressures wild stocks have,” Ruggerone said. “They’ve undergone domestication, there’s less genetic variability, and they probably are less adaptable when the environmental changes.”
Despite the boost in salmon returns in the Columbia River this year, areas such as British Columbia’s Fraser River remain a puzzle. After three straight years of exceedingly low sockeye returns, this year’s salmon runs in the Fraser River exceeded expectations.
“This finding does not negate the real observations that many stocks not only are low, they’re low enough to be concerned about,” Peterman said. “A good analogy is the stock market index – there’s a composite index, but in that mix there are some losers. Some go way down, and others way up.”
The article said that British Columbia salmon migrate into the Pacific Ocean and to the Gulf of Alaska, and intermingle with hatchery fish from Japan and Alaska. “Unilateral actions by various hatcheries is having detrimental affect on salmon everywhere,” he said.