Contact: Brian Gorman FOR IMMEDIATE RELEASE
April 17, 1996
A blue-ribbon panel of experts has released a report that evaluates and suggests ways to improve a federal program to monitor gas-bubble disease in young salmon in the Snake and Columbia rivers.
The nine-member panel, convened last February at the Northwest Fisheries Science Center in Seattle, said the National Marine Fisheries Service's monitoring program should continue until important scientific uncertainties are better understood. These include the relationship between symptoms of gas-bubble disease and fish mortality, the best locations for sampling fish and estimates of how many young fish survive in the river when gas levels are high.
William Stelle, director of the fisheries service's Northwest region in Seattle, said the panel's recommendations are being incorporated into the agency's gas-bubble research and monitoring programs for 1996.
"Sound science must be the foundation for all our decisions about salmon recovery in the Columbia River basin," Stelle said. "Getting answers to questions about gas-bubble disease is a crucial part of that foundation if we're going to make rational, informed choices about how best to operate the basin's hydroelectric system."
During the spring and summer, water is sometimes intentionally spilled at hydroelectric dams to divert juvenile salmon past the electricity-generating turbines, because about 10 percent of salmon may be killed when they go through the turbines. In addition, sometimes river managers are forced to spill water at dams because the volume of water in the river is so high that it cannot all be sent through the turbines.
Whether spills are intentional or forced, however, the spilled water can trap large amounts of air and force it into a dissolved state, sometimes resulting in gas-supersaturated water, much like the carbon dioxide gas in a bottle of soda.
When migrating young salmon are exposed to these high levels of dissolved gas, they can develop a condition known as gas-bubble disease, similar to the "bends" that can afflict scuba divers. In extreme cases, the condition can kill fish. Even at lower levels, gas-bubble disease can reduce a fish's ability to avoid predators, increase its susceptibility to disease, and impair its swimming performance.
Questions about the risks of gas-bubble disease are important, fishery biologists say, because the alternatives to getting young salmon downriver to the ocean -- diverting fish around dams with "bypass" systems, collecting fish in barges to be transported past the dams or allowing fish to pass directly through the turbines -- also pose risks. The goal of research, according to the fisheries service, is to determine which alternatives pose the least risk, depending on the flow conditions of the river and other variable factors.
The panel is made up of experts from the Columbia River Inter- Tribal Fish Commission, Oak Ridge National Laboratory, National Marine Fisheries Service, U.S. Geological Survey, Canada's Department of Fisheries and Oceans and several private consulting firms.
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