Wenatchee River Salmon Escapement Estimates Using Video Tape Technology in 1992
Accurate determination of escapement is necessary for fish stock status analysis. In an effort to devise a more accurate salmon escapement estimation technique, a time-lapse video tape recording system was installed and operated from 11 May, 1992 through 11 September, 1992, in the fish counting station at Tumwater Dam on the Wenatchee River. This was a continuation of studies conducted annually since 1989.
In 1992, Wenatchee River salmon escapement above Tumwater Dam was estimated to be 20,026 and 3,802 for sockeye Oncorhynchus nerka and chinook salmon O. tshawytscha, respectively. Salmon migratory timing estimates have remained similar from 1989 through 1992. The mean dates of passage for salmon in 1992 were 21 July (SD = 10.0) for sockeye, and 9 July (SD = 22.0) for chinook. Nighttime sockeye salmon passage estimates accounted for 6.2% of the run. That percentage is similar to estimates made in previous years at Tumwater Dam and at Bonneville Dam in 1973 and 1974.
Estimating salmon escapement using time-lapse video technology has been successful at Tumwater Dam on the Wenatchee River, Washington. Our findings indicate that by implementing video counting at other locations where salmon passage is monitored, fish count accuracy would likely increase because nighttime passage could be monitored with little additional effort. Also, individual specimen identification would be more precise, and a permanent record of fish passage events would be created.
Hatch, D.R., A. Ward, and M. Schwartzberg. 1993. Wenatchee River Salmon Escapement Estimates using Video Tape Technology in 1992. Columbia River Inter-Tribal Fish Commission Technical Report No. 93-5.