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Study: dams can benefit California salmon runs

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Study: dams can benefit California salmon runs

Postby ERIC » Thu May 01, 2008 7:41 am

Study suggests dams can benefit California salmon runs by releasing cold water as fish spawn

The Associated Press
Published: May 1, 2008


SACRAMENTO, California: California's vast network of reservoirs — which destroyed more than 5,000 miles (8,000 kilometers) of salmon habitat when their dams were erected decades ago — could turn out to be a savior for a species on the brink of collapse, according to a new study.

Those dams store cold water, which the study says will be vital to the salmon's survival as climate change is expected to warm California's rivers.

"Paradoxically, the very thing that is constraining fish now, we could use those to our advantage," said study author David Yates, a project scientist at the National Center for Atmospheric Research in Boulder, Colorado.

The peer-reviewed paper will appear in a future issue of the Journal of Climatic Change. Yates and the journal agreed to release the study's findings early to The Associated Press.

It comes at a time when the number of salmon returning to spawn in state's Central Valley rivers, crucial to U.S. West Coast stocks, are at historic lows.

Earlier this month, federal fisheries regulators recommended that fishing along California's coast and most of Oregon be suspended for the year. It was the first time the Pacific Fishery Management Council had taken such a drastic step, one that is jeopardizing the $150-million (€100-million) West Coast salmon industry.

Unfavorable ocean conditions, habitat destruction, dam operations, agricultural pollution and climate change are among the potential causes.

Historically, 1 million to 3 million chinook salmon spawned annually in the streams that tumbled out of the western Sierra Nevada mountains. This year, just 50,000 are expected to return to the Central Valley river systems.

Studies have shown that high water temperatures have wide-ranging and potentially fatal consequences for salmon, who generally need water temperatures lower than 68 degrees (20 Celsius) when they return to fresh water. It reduces their swimming ability, increases their vulnerability to disease and leads to lower growth rates. Spawning females require even colder water of 57 degrees (14 Celsius) for their eggs to live and juvenile salmon migrate back to the ocean more successfully when the river is no more than 64 degrees (18 Celsius).

Higher water temperatures can be offset if federal water managers preserved the cold water stored behind Shasta Dam, near the head of the Sacramento River, and released it when the salmon head upriver. Salmon that once headed far upstream to cooler, mountain streams are now forced to spawn in valley waters because the dam blocks their path.

State scientists say climate change could lead to more winter flooding, summer droughts, warmer rivers and streams, and rising seas that will push salt water farther upstream from San Francisco Bay.

Temperature spikes are particularly worrisome for cold water fish such as salmon, steelhead and the state fish, the California golden trout, according to research compiled in the National Wildlife Federation report.

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