Salmonid Field Protocols Handbook: Techniques for Assessing Status and Trends in Salmon and Trout

Video Methodology

Jennifer S. O’Neal

doi: https://doi.org/10.47886/9781888569926.ch23

Video equipment has been used to assess aspects of migrating salmonids since about 1990. Efforts to assess abundance of salmonid species more accurately have intensified due to declines in many stocks. Additionally, management of stocks requires the accurate assessment of abundance and the diversity of species in freshwater systems. In assessing adult salmon moving upstream, video surveys are well suited as an alternative to manual counting at fishways and dams (Hatch et al. 1994; Hiebert et al. 2000). Manual counts require significant staff time during the migration season, and video surveys have been tested as an alternative approach to reduce this staff time requirement.

Video surveys have been successfully applied in remote areas where tower counts or aerial surveys have generally been conducted (see Figure 1). Aerial surveys have been used in Alaska to assess salmon populations over large areas using relatively little staff time, but variable conditions and observer variability limit the accuracy of these counts (Otis and Dickson 2002). Data from aerial surveys are often a rough estimate and therefore may not be suitable for measuring abundance, productivity, or recovery of salmon populations; this information should be considered an index rather than a true measure of adult escapement (Hetrick et al. 2004).

Counts at weirs are used as another way to track both upstream migration of adult salmon as well as downstream migration of smolts. While weir counts provide the most accurate assessment of migrating fish populations through a freshwater system, their operation requires daily monitoring and maintenance. Additionally, weirs can be overtopped by high flows or damaged by debris. In an attempt to address issues of cost and the ability to provide a permanent record of fish counted, video equipment has been used to count and establish species composition for a variety of salmonid species.

Video techniques have also been used to assess the movement (including leaping ability) of juvenile coho salmon Oncorhynchus kisutch at culvert outfalls (Pearson et al. 2005). This work is particularly relevant as very large numbers of perched culverts are blocking upstream fish passage to thousands of kilometers of stream habitat.

Deepwater spawning of fall chinook salmon O. tshawytscha downstream of the Bonneville Dam on the Columbia River was assessed using video-based boat surveys (Mueller 2005). A total of 293 redds were detected in a 14.6-ha area; an expanded redd count based on the percentage video coverage of the area was 3,198 redds. Chinook redds were found 1.07–7.6 m deep in predominately medium-cobble substrate.

A particularly thorough and practical review of video and acoustic camera technologies for studying fish under ice has come from Mueller et al. (2006). These researchers have examined fish species presence, abundance, size, and behavior under ice cover in northern and arctic lakes, rivers, and streams.