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New paper examines dams' effects on California salmon
September 25, 2007DURHAM, N.C. -- Spring-run Chinook salmon and other fish in the rivers of California's 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 NOAA's 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 of dams on spatial connectivity among Chinook populations. In addition, they established the spatial structure of the current surviving 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 dam, 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 noted. "This pathway highlights dams whose removal would have the greatest positive impact on the species."
The methods he and Lindley employed to do their analysis can be applied broadly across taxa and systems, he added, and would be useful tools for scientists, policymakers and environmental managers in California who want a better understanding of the structure and function of impaired ecosystems.
"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.
Duke University
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 NOAA's 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 of dams on spatial connectivity among Chinook populations. In addition, they established the spatial structure of the current surviving 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 dam, 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 noted. "This pathway highlights dams whose removal would have the greatest positive impact on the species."
The methods he and Lindley employed to do their analysis can be applied broadly across taxa and systems, he added, and would be useful tools for scientists, policymakers and environmental managers in California who want a better understanding of the structure and function of impaired ecosystems.
"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.
Duke University
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Salmon migration mystery explored on Idaho's Clearwater River
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Northwestern United States could face more tamarisk invasion by century's end
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Widespread Occurrence of Intersex Bass Found in U.S. Rivers
Intersex in smallmouth and largemouth basses is widespread in numerous river basins throughout the United States is the major finding of the most comprehensive and large-scale evaluation of the condition, according to U.S. Geological Survey (USGS) research published online in Aquatic Toxicology.
River flow and temperature limit trout numbers
Over a 23-year study, Javier Lobon-Cervia has found the mechanism that controls the number of salmonids found each year in Cantabrian rivers.
Half of the fish consumed globally is now raised on farms, study finds
Aquaculture, once a fledgling industry, now accounts for 50 percent of the fish consumed globally, according to a new report by an international team of researchers. And while the industry is more efficient than ever, it is also putting a significant strain on marine resources by consuming large amounts of feed made from wild fish harvested from the sea, the authors conclude.
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