New California Dams and Salmon

New California Dams and Salmon



2007 September -   Spring-run Chinook 
salmon and other fish in the rivers of California’s Central Valley could 
be hurt by more water storage dams, according to researchers at Duke 
University and the National Oceanic and Atmospheric Administration, NOAA. 
The scientists believe the findings of their research may serve to caution 
policymakers, scientists and resource managers currently debating the 
construction of two new dams and the expansion of a third proposed last 
week by California Governor Arnold Schwarzenegger in a $9 billion plan to 
ease the state's water crisis. 
Robert 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. 
He 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 Lindley of NOAA’s Southwest Fisheries Science Center in Santa Cruz, 
California. 
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 of dams on spatial connectivity among Chinook populations. 
In addition, they established the locations of the current surviving 
salmon populations in the Central Valley. 
"We were able to document reduced spatial and demographic connectivity 
between salmon populations in the rivers as a result of the dams, and we 
identified several populations that had become vulnerable to, and 
dependent upon, production in fish hatcheries," Schick said. 
In addition to identifying problems linked to the dams, their network 
analysis identified potential solutions. 
"By highlighting the demographic impact of individual populations of fish, 
network science allowed us to propose a recovery pathway for spring-run 
Chinook salmon in the Central Valley," Schick said. 
"This pathway highlights dams whose removal would have the greatest 
positive impact on the species," he said. 
"We feel our work documents the harmful role of dams on spring-run Chinook 
salmon and can be used as a cautionary tale," he said. 
The paper, "Directed Connectivity Among Fish Populations in a Riverine 
Network," was published in the September 3 online issue of "Journal of 
Applied Ecology." To read it online click here. 

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