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The Problem
The Chief Joseph Kokanee Enhancement Project was initiated in 1995 by the Colville Confederated Tribes to determine the stock status of kokanee above Chief Joseph and Grand Coulee dams. Subsequently, an entrainment study at Grand Coulee Dam indicated that 200,000 - 600,000 kokanee were entrained, primarily at the 3rd powerhouse, during a 40-month time period. Therefore, the entrainment of resident salmonids at Grand Coulee Dam was identified as a management problem to be solved in the coming years. Following the recommendations of the Independent Scientific Review Panel, research was initiated to investigate a strategy to reduce entrainment by using strobe lights to repel salmonids away from the 3rd powerhouse at Grand Coulee Dam. The research conducted under this study corresponds to reimbursable agreement number 00004767. Objectives Our objective is to evaluate the behavioral response of kokanee salmon and rainbow trout to strobe lights. Methodology
The Columbia River Research Laboratory is evaluating the effectiveness of strobe lights using fish telemetry techniques to locate and track the movements of acoustic-tagged Kokanee. The method provides precise information about fish position. The telemetry data will provide species-specific time series information on an individual fishs movement behavior. The 3-D position of acoustic-tagged fish will be monitored over time to study the Kokanee movement response to strobe light operation. Highlights and Key Findings Within our fixed hydrophone array located in the cul-de-sac of the third powerhouse, we detected 15 kokanee salmon and 34 rainbow trout during 3 of the 8 treatment blocks for which we collected data. Kokanee had a median residence time within the array of 0.36 h and rainbow had a median residence time of 2.1 h. There were approximately equal numbers of fish and number of detections during the day and night, and during the strobe on and off treatments. We observed differences in the spatial distribution of kokanee detections among strobe light treatments and diel periods. When the strobe lights were on, the mean depth of kokanee was deeper than when the strobe lights were off for both day and night periods. We observed one potential example of entrainment where a kokanee salmon entered the array at a shallow depth and descended to a potential entrainment depth near a turbine intake. Between treatments and day/night, we detected nearly equal numbers of rainbow within 25 m of the strobe light, although no kokanee were detected within 25 m of the strobe lights when they were on. Mean depth distributions above and below the strobe lights showed that a high proportion of the tagged rainbow trout were at the depth of the strobe light (10 m). The directional vectors, number of detections, residence time, and swimming velocities within 25 m of the strobe light suggest that rainbow were attracted to the strobe lights. Where Are We Headed In 2003 Data analysis and report writing will take place in 2003. Project Contact Dennis Rondorf Email: dennis_rondorf@usgs.gov Publications |
