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NW Fishletter #223, November 20, 2006

[5] Scientist Says Dams May Not Be Limiting Fish Recovery

A presentation by a federal fisheries scientist at a conference at Yale University earlier this month has raised questions over the notion, held by many, including the federal judge overseeing the remand process of the Columbia River hydro BiOp, that ESA-listed salmon runs are still declining with the lower Snake dams in place.

NOAA Fisheries' John Williams, from the agency's science center in Seattle, told participants at the "Global Perspectives on Large Dams" section of the Conference on Large-Scale Water Infrastructure that improvements in fish survival at dams have helped the stocks in recent years. By spilling water, barging fish, and modifying dams and their operations, inriver survivals for spring chinook have been pretty steady over the past 10 years, especially when compared to adult returns, which have been heavily influenced by changes in ocean conditions.

Williams presented a graph that tracked "natural" fall Chinook returns back to Lower Granite Dam and showed a huge boost since 2000 over the previous 25 years.

(Courtesy NOAA Fisheries)

His main message was that all fish populations, from anchovies and sardines to salmon show significant natural fluctuations. He noted that in the late 1820s, settlers and Indians in the mid-Columbia region resorted to eating horses after the wholesale failure of salmon runs, pointing to poor ocean conditions as the only explanation.

Williams also explained that overall spring chinook return rates are as high as those observed before most of the lower Snake dams were built. He raised important questions after plotting harvest rates on spring and fall Chinook over the past 30 years which seemed to indicate that return rates improved as harvest rates fell. "Could we harvest adults at higher rates without dams" or "Is recovery limited by dams?" If the answer was clear, he said, 'the debate would not rage." -B. R.

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