New paper examines dams' effects on Califor...( DURHAM N.C. -- Spring-run Chinook sa...)

DURHAM, N.C. -- Spring-run Chinook salmon and other fish in the rivers of Californias Central Valley could be harmed by more water-storage dams, according to researchers at Duke University and the National Oceanic and Atmospheric Administration.

The findings of a recent paper may serve as a cautionary tale to policymakers, scientists and resource managers currently embroiled in a debate about the construction of new dams in the region.

The paper, Directed Connectivity Among Fish Populations in a Riverine Network, was published in the September 3 online issue of Journal of Applied Ecology.

Robert S. Schick, of the University Program in Ecology at Duke's Nicholas School of the Environment and Earth Sciences, used analytical techniques from network science to study the relative importance of individual populations of salmon within the valley and examined how the addition of large water-storage dams blocked access to habitat and fragmented these populations over time.

"We found that fragmented populations became increasingly vulnerable to disturbance and extinction," said Schick, who co-wrote the paper with Steven T. Lindley of NOAAs Southwest Fisheries Science Center in Santa Cruz, Calif.

The paper has become topical thanks to a recent $9 billion bond proposal by California Gov. Arnold Schwarzenegger to construct two new dams and expand a third in the environmentally fragile Sacramento-San Joaquin River Delta.

Schwarzenegger says the new dams could help alleviate water-shortage problems associated with frequent droughts in the region. Some money from the bond would be used to pay for conservation improvements such as increased seasonal river flows to aid Delta Smelt, salmon and other species of fish that live in the delta area or swim upriver to spawn.

After first establishing the historical structure of the San Joaquin and Sacramento River systems, Schick and Lindley studied the progressive impact
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