Salmon hatcheries can deplete wild stocks | Science News

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Salmon hatcheries can deplete wild stocks

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11:14am, May 30, 2001

Each year, hatcheries release millions of chinook into the Columbia River system in a bid by state game managers to save wild stocks of this salmon. The fish there is so beleaguered that many of its populations, threatened with extinction, are protected under the Endangered Species Act. A new study now offers evidence that hatchery fish may be hastening the wild stocks' demise.

Phillip S. Levin and his colleagues with the National Marine Fisheries Service (NMFS) in Seattle analyzed chinook-population data spanning the past quarter century for the Snake River, which feeds into the Columbia. Some 18 months after the fall spawning of chinook, a river of smolts heads for the ocean, where the young fish will spend the next 4 or more years.

The Seattle scientists compared releases of hatchery-reared smolts with data on the number of returning wild adults.

The team also noted fluctuations in food available for the smolts once they reach the ocean. Measures of the local o

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