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The Problem As anadromous juvenile salmonids migrate from freshwater rearing habitats to the ocean, they are vulnerable to a host of factors that affect their survival. Direct effects associated with dam passage (e.g., instantaneous mortality, injury, loss of equilibrium, etc.) and indirect effects (e.g., predation, disease, and physiological stress) contribute to the total mortality of seaward migrating salmonids. Many studies have been conducted to determine the effects of hydroelectric dams on the survival of salmonid migrants. Based on this research and studies examining migrant salmonid behavior at dams in the Columbia River Basin, management actions are currently being implemented to improve the survival of juvenile salmonid migrants.
Radio telemetry has been used extensively to evaluate the survival of fish and wildlife populations and to monitor the behavior and passage routes of yearling and sub-yearling chinook salmon Oncorhynchus tshawytscha and juvenile steelhead O. mykiss through hydroelectric projects in the Columbia River Basin. Detection rates of marked fish affect the sample size required for a given level of precision and thus, the reliability of survival estimates. Similar to the advantages provided by Passive Integrated Transponder (PIT) tags over other marking techniques, the high detection rates observed in radio-telemetry studies of migrant salmonids in the lower Columbia River suggest that the numbers of fish necessary to generate survival estimates with similar or greater precision could be reduced using radio-tagged fish. Recent technological advancements in radio-telemetry equipment have decreased the size and increased the life of transmitters, eliminating many of the past problems associated with using this technique. Further, in areas where PIT-tag survival estimates continue to be generated, the use of radio telemetry would provide a means of validating these estimates using a different technique. Objectives The objective of this study has been to evaluate the survival of juvenile yearling and sub-yearling chinook salmon and steelhead trout through various passage routes at The Dalles Dam. Methodology
Radio-telemetry systems are installed at hydroelectric projects and at various locations along the Columbia River. Juvenile salmonids are then tagged and released at pre-determined locations based on the research questions posed by fish and water managers. As the radio-tagged fish migrate downstream they are interrogated with the radio-telemetry systems. Data collected with these systems are processed and subjected to QA/QC protocols before being analyzed. Survival estimates are then generated using the statistical methods described in the following publications:
Highlights and Key Findings Past studies at The Dalles Dam have been designed to evalaute the effects of passing under differeing dam operation conditions and through various routes at this hydroelectric project. The information from these studies is routinely evaluated by federal, state, and tribal management agencies and used to formulate strategies that will improve the survival of juvenile salmon and thus, aid in the recovery of endangered salmon populations in the Columbia River Basin. Results from 2002 evaluations suggest decreased survival of yearling chinook salmon passing through different spillbays at the spillway. The null hypothesis tested during this experiment (Ho: There is no difference in survival for fish passing via north and south spillbays) was formulated based on observations that fish passing via the northern most spillbays may be laterally transported across the face of the spillway and thus, be subjected to either physical injury or increased predation risks. Our results suggested that fish passing via the northern spillbays did indeed have lower survival than fish passed via southern spillbays. Based on this result, the Army Corps of Engineers and other entities charged with formulating mitigation strategies for endangered stocks of chinook salmon are developing alternate spill basin configurations strategies at this project. Where Are We Headed In 2003 No evaluations are planned for 2003. Project Contact Tim Counihan Email: tim_counihan@usgs.gov Publications |
