Total Dissolved Gas Effects on Incubating Chum Salmon Below Bonneville Dam

摘要

At the request of the U.S. Army Corps of Engineers (USACE; Portland District), Pacific Northwest National Laboratory (PNNL) undertook a project in 2006 to look further into issues of total dissolved gas (TDG) supersaturation in the lower Columbia River downstream of Bonneville Dam. In FY 2008, the third year of the project, PNNL conducted field monitoring and laboratory toxicity testing to both verify results from 2007 and answer some additional questions about how salmonid sac fry respond to elevated TDG in the field and the laboratory. For FY 2008, three objectives were 1) to repeat the 2006-2007 field effort to collect empirical data on TDG from the Ives Island and Multnomah Falls study sites; 2) to repeat the static laboratory toxicity tests on hatchery chum salmon fry to verify 2007 results and to expose wild chum salmon fry to incremental increases in TDG, above those of the static test, until external symptoms of gas bubble disease were clearly present; and 3) to assess physiological responses to TDG levels in wild chum salmon sac fry incubating below Bonneville Dam during spill operations. This report summarizes the tasks conducted and results obtained in pursuit of the three objectives.