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Published: 2004

Total Pages: 34

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Accurate determination of adult salmon spawner abundance is key to the assessment of recovery actions for wild Snake River spring/summer Chinook salmon (Onchorynchus tshawytscha), a species listed as 'threatened' under the Endangered Species Act (ESA). As part of the Bonneville Power Administration Fish and Wildlife Program, the Nez Perce Tribe operates an experimental project in the South Fork of the Salmon River subbasin. The project has involved noninvasive monitoring of Chinook salmon escapement on the Secesh River between 1997 and 2000 and on Lake Creek since 1998. The overall goal of this project is to accurately estimate adult Chinook salmon spawning escapement numbers to the Secesh River and Lake Creek. Using time-lapse underwater video technology in conjunction with their fish counting stations, Nez Perce researchers have successfully collected information on adult Chinook salmon spawner abundance, run timing, and fish-per-redd numbers on Lake Creek since 1998. However, the larger stream environment in the Secesh River prevented successful implementation of the underwater video technique to enumerate adult Chinook salmon abundance. High stream discharge and debris loads in the Secesh caused failure of the temporary fish counting station, preventing coverage of the early migrating portion of the spawning run. Accurate adult abundance information could not be obtained on the Secesh with the underwater video method. Consequently, the Nez Perce Tribe now is evaluating advanced technologies and methodologies for measuring adult Chinook salmon abundance in the Secesh River. In 2003, the use of an acoustic camera for assessing spawner escapement was examined. Pacific Northwest National Laboratory, in a collaborative arrangement with the Nez Perce Tribe, provided the technical expertise to implement the acoustic camera component of the counting station on the Secesh River. This report documents the first year of a proposed three-year study to determine the efficacy of using an acoustic camera to count adult migrant Chinook salmon as they make their way to the spawning grounds on the Secesh River and Lake Creek. A phased approach to applying the acoustic camera was proposed, starting with testing and evaluation in spring 2003, followed by a full implementation in 2004 and 2005. The goal of this effort is to better assess the early run components when water clarity and night visibility preclude the use of optical techniques. A single acoustic camera was used to test the technology for enumerating adult salmon passage at the Secesh River. The acoustic camera was deployed on the Secesh at a site engineered with an artificial substrate to control the river bottom morphometry and the passage channel. The primary goal of the analysis for this first year of deployment was to validate counts of migrant salmon. The validation plan involved covering the area with optical video cameras so that both optical and acoustic camera images of the same viewing region could be acquired simultaneously. A secondary test was contrived after the fish passage was complete using a controlled setting at the Pacific Northwest National Laboratory in Richland, Washington, in which we tested the detectability as a function of turbidity levels. Optical and acoustic camera multiplexed video recordings of adult Chinook salmon were made at the Secesh River fish counting station from August 20 through August 29, 2003. The acoustic camera performed as well as or better than the optical camera at detecting adult Chinook salmon over the 10-day test period. However, the acoustic camera was not perfect; the data reflected adult Chinook salmon detections made by the optical camera that were missed by the acoustic camera. The conditions for counting using the optical camera were near ideal, with shallow clear water and good light penetration. The relative performance of the acoustic camera is expected to be even better than the optical camera in early spring when water clarity and light penetration are limited. Results of the laboratory tests at the Pacific Northwest National Laboratory facility indicated that the detection rate for the acoustic camera system was essentially 100% across all levels of turbidity in the experiments. Overall, the acoustic camera outperformed the optical camera at detecting fish, both in the laboratory tank and at the Secesh River fish counting station. However, the optical camera approach still offers some advantages over the acoustic camera under certain limited circumstances. The primary advantages are better species, gender and condition determination and better separation of debris from fish moving downstream. Using both systems in parallel will provide the most robust and accurate platform for counting fish in the field by exploiting the relative strengths of both systems through the season.