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

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 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.

Comparing on site human and video counts at Igarapava fish ladder, south eastern Brazil

“…It allowed monitoring the fish passage and the assurance of counts (Irvine et al, 1991;Hatch et al, 1994). The videotape system can make it easier, faster, and less expensive to count migratory fish passage (Irvine et al, 1991).…”

“…The observer could also play the tape back an unlimited number of times and at varying speeds, and show the film to other fisheries professionals to confirm species identification (Hatch et al, 1994;Travade & Larinier, 2002). This was not an option for the human observers in real time at the IDFL window.…”

“…The degree of confidence that may be placed in such estimates is impossible to estimate both for the number of fish passing and for individual specimen identification (Hatch et al, 1994, Hatch et al, 1998 Recent progress with video technology has allowed automation and reduced the need for visual counting carried out by observers in situ (Travade & Larinier, 2002). Timelapse video systems have been used to record migration of adult Pacific salmon (Hatch et al, 1994). This technique provides the opportunity to calculate variance and place confidence bounds on estimates.…”

“…In most situations, time-lapse recorded video tapes of fish passage contain only a small percentage of frames of actual fish images. However, a counter must review all tape frames, no matter how many fish are present (Hatch et al,1994). Computerized image processing techniques have many potential applications for the analysis of fish passage (Travade & Larinier, 2002).…”

Enumeration of Salmonids in the Okanogan Basin Using Underwater Video, Performance Period: October 2005 (Project Inception) - 31 December 2006.

“…Fish enumeration programs throughout the Columbia River Basin have shifted to using time-lapse and motion detection video monitoring equipment due to its wide ranging applications (Irvine et al 1991;Hatch et al 1994b;Hiebert et al 2000;Otis and Dickson 2001;Faurot and Kucera 2002;Anderson et al 2004;Hetrick et al 2004). Unlike mark/recapture studies, underwater video sampling requires no handling of fish and is a passive, non-invasive process that can potentially operate continuously throughout the year.…”