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 tested, 48‐h and 72‐h modes. The amount of nighttime fish passage, measured between 2000 and 0400 hours, was estimated and averaged for each species over the three study years. Mean values ranged from 6.68 to 16.24%, which indicated that a significant portion of salmon migration at Tumwater Dam occurred at night. An additional test that compared these observations with those of a study of nighttime salmon passage at mainstem Columbia River dams suggested that the ratio of nighttime passage to that of the previous day was similar among study sites. The videotape system appeared to be a useful method for estimating Pacific salmon escapement, which offered several important advantages over on‐site counting. These advantages include improved accuracy, a permanent record of migration, and cost efficiencies that are particularly noteworthy in areas of low escapement. Also, a video record of salmon migration can be used to calculate bounded escapement estimates, and individual specimen identification can be confirmed. The tape analysis process of counting and identifying fish can be automated by means of a computerized image‐processing system.

Scale pattern analysis (SPA) was used to differentiate hatchery and natural-origin stocks of spring-run chinook salmon Oncorhynchus tshawytscha of age 1.2 (= age 4; spent one winter as juveniles in fresh water and two winters in the ocean; one winter of egg incubation is implied) from the Snake, Wenatchee, and Deschutes subbasins of the Columbia River basin. Linear discriminant analyses indicated that hatchery and natural-origin stocks within each subbasin could be identified with a relatively high degree of accuracy. High classification accuracies were also obtained by comparing pooled hatchery stocks from the three Columbia River subbasins with pooled natural-origin stocks from those same subbasins. For a composite mixed-stock analysis, samples of unknown origin were obtained from Bonneville Dam, a site on the lower Columbia River where a mixed population of spring chinook salmon stocks is found. This analysis, which was done with a classification model based on pooled hatchery and natural-origin stocks, estimated that 71% (90% confidence intervals of 61-81%) of age-1.2 spring chinook salmon sampled at Bonneville Dam were of hatchery origin. The classification model used in the mixed-stock analysis was derived from a limited set of representative samples of known stocks. Estimating hatchery and natural-stock composition of mixed-stock populations by using SPA and a limited set of representative known-stock samples is a potentially valuable technique for management of Columbia basin spring chinook salmon. This technique may also prove applicable to management of other mixed-stock Pacific salmon populations.

We designed and tested a videotape editing system that selected and removed video frames not containing fish images from source videotapes previously recorded in 24, 48, or 72 h time‐lapse modes. The system, based on image‐processing software and a personal computer, compressed videotapes of the passage of Pacific salmon Oncorhynchus spp. by 75% (±6.8%). The system reduced the length of tape that had to be reviewed without significantly altering fish counts made from the tapes. Fish counts made from visual review of both the edited and source videotapes were similar (P = 0.925). Using stratified random sampling, we selected and edited a sample of 200 d of recordings made at five different locations. The combined location and time data formed a 1,890‐d statistical population of fish passage. This sample of source tapes was stratified post hoc into three different categories of fish‐passage densities, measured by the number of fish on every 24 h of recorded tape (<100, 100–400, and >400 fish/d). Source tape compression was inversely related to fish passage density. The editing system processed and compressed source videotape recordings representing 24 h of monitoring at a particular site in approximately 2 h. The system was simple to use and did not require operator attention during the automated editing process. The videotape editing system can make it easier, faster, and less expensive to review videotapes of migratory fish passage and is most useful at locations or during times when relatively few fish will be observed per day.