Oregon Hatchery Research Centre. (Photo: dfw.state.or.us)
Hatchery salmon threaten wild salmon survival: studies
Tuesday, May 15, 2012, 23:20 (GMT + 9)
More than 20 studies by leading university scientists and government fishery researchers offer swelling evidence that salmon raised in man-made hatcheries can harm wild salmon stocks as the fish compete for food and habitat.
The studies were conducted by researchers in Alaska, British Columbia, Washington, Oregon, California, Russia and Japan.
"The genetic effects of mixing hatchery fish with wild populations have been well-documented," said David Noakes from Oregon State University. "But until now the ecological effects were largely hypothetical. Now we know the problems are real and warrant more attention from fisheries managers."
Published in the May issue of Environmental Biology of Fishes, the research volume gathers 23 peer-reviewed, independent studies done across the entire range of Pacific salmon.
The research suggests questions about whether the ocean can supply enough food to sustain wild salmon if there are further increases in hatchery fish.
"This isn't just an isolated issue," says Pete Rand, a biologist at the Wild Salmon Centre and a guest editor of the publication. "What we're seeing here in example after example is growing scientific evidence that hatchery fish can actually edge out wild populations."
|Oregon fish pond. (Photo: dfw.state.or.us/ODFW)
Fewer wild salmon would mean less of the genetic diversity that has allowed salmon to evolve and thrive. Unlike hatchery fish, wild salmon populations have highly specialized adaptations to the natural environment that enhance their ability to endure environmental changes like higher ocean temperatures and extreme variations in stream flows.
For decades, hatchery programmes in the US, Canada, Russia and Japan have released billions of fish into the wild -- and the increasing global demand for salmon may lead to further hatchery production.
"Five billion juvenile salmon are released each year worldwide, and the prospect of additional increases in hatchery production is worrisome for the long-term survival of wild salmon," Rand said.
Scientists are also seeing startling interactions across oceans. One of the studies shows that chum salmon released from hatcheries in Asia have provoked declines in a wild chum salmon population 2,500 mi away in western Alaska.
"Genetic data show that these fish share the same feeding grounds in the open waters of the Bering Sea and North Pacific Ocean," stated author Greg Ruggerone of Natural Resources Consultants. "With billions of hatchery chum released each year, the abundance of adult chum salmon from hatcheries is now much greater than wild chum salmon, so it is not all that surprising that we are seeing evidence of competition in the North Pacific."
Further, recent climate shifts have made ocean conditions better able to support large populations of salmon, but as these patterns continue to change, food for salmon in the ocean may plummet, making it even harder for wild fish to survive.
Many scientists have thus noted the need for a new international agreement or treaty to address the expansion of hatchery salmon in the North Pacific.
- Wild salmon populations weaker than previously thought: study
By Natalia Real