A Computerized Editing System for Video Monitoring of Fish Passage

Abstract

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.

Adult Chinook Salmon Abundance Monitoring in Lake Creek, Idaho, Annual Report 2001.

“…In 2001, completed Lake Creek videotapes were taken immediately to the office where they were manually reviewed for proper operation and data obtained. The computerized editing system for video monitoring of fish passage described in Hatch et al (1998) Species identification was fairly simple. All adult chinook salmon were 50 cm or larger.…”

“…The computerized editing system for video monitoring of fish passage described in Hatch et al (1998) did not work again for our system in 2001. It has been a constant struggle to provide bright, even lighting at night and to prevent bright uneven lighting during the day.…”

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

“…The videotape system can make it easier, faster, and less expensive to count migratory fish passage (Irvine et al, 1991). It is most useful at locations or during times when relatively few fish will be observed per day (Hatch et al, 1998) as it avoids the need for full-time human observers.…”

“…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).…”

“…Video technology provides a permanent record of fish passage that can be reviewed multiple times by different readers to obtain accurate species and number of fish using the fish pass. Video fish counting can also reduce data gathering costs and increase the amount of data collected compared with on-site counting (Hatch et al, 1998). In most situations, time-lapse recorded video tapes of fish passage contain only a small percentage of frames of actual fish images.…”