Estimation of Pacific Salmon Escapement with a Time-Lapse Video Recording Technique

Abstract

Abstract A time-lapse video system was designed and used to record the migration of adult Pacific salmon at Tumwater Dam on the Wenatchee River, Washington. From 1989 through 1991, the system was evaluated to determine its suitability and usefulness for escapement estimation of three Pacific salmon species, chinook salmon Oncorhynchus tshawytscha, sockeye salmon O. nerka, and steelhead O. mykiss. The accuracy and precision of estimates based on these videotape records were tested. Video-based sockeye salmon escapement estimates were found to be within 4% of an independent estimate based on the on-site visual counts made by experienced observers. An among-observer variance test was performed comparing the counts of five different individuals who examined the same videotape records. Analysis of variance showed no significant differences among the five observers. A test that compared the effect on counts of different time-lapse recording speeds indicated no significant differences between the two speeds test...