Measuring fish and their physical habitats: versatile 2D and 3D video techniques with user-friendly software

Abstract

Applications of video in fisheries research range from simple biodiversity surveys to three-dimensional (3D) measurement of complex swimming, schooling, feeding, and territorial behaviors. However, researchers lack a transparently developed, easy-to-use, general purpose tool for 3D video measurement and event logging. Thus, we developed a new measurement system, with freely available, user-friendly software, easily obtained hardware, and flexible underlying mathematical methods capable of high precision and accuracy. The software, VidSync, allows users to efficiently record, organize, and navigate complex 2D or 3D measurements of fish and their physical habitats. Laboratory tests showed submillimetre accuracy in length measurements of 50.8 mm targets at close range, with increasing errors (mostly <1%) at longer range and for longer targets. A field test on juvenile Chinook salmon (Oncorhynchus tshawytscha) feeding behavior in Alaska streams found that individuals within aggregations avoided the immediate proximity of their competitors, out to a distance of 1.0 to 2.9 body lengths. This system makes 3D video measurement a practical tool for laboratory and field studies of aquatic or terrestrial animal behavior and ecology.

Foraging behaviour and optimal microhabitat selection in Yukon River Basin nonanadromous Dolly Varden Charr (Salvelinus malma)

“…Dolly Varden rarely failed to capture prey in experiments, and capture velocity represented the velocity of drifting prey when caught by a test fish. We estimated capture velocity by marking the prey item at any point where visible in trial videos and again at the point of capture and used VidSync (Neuswanger et al, ) to calculate the elapsed time and distance between those two points. The strong linear relationship and high correlation between prey capture velocities and treatment velocities ( R 2 = 0.97, y = 0.89 x + 3.47) is evidence that our treatment velocities delivered prey at the desired velocity throughout the duration of trials.…”

“…On rare occasions when an individual held position at multiple locations during a trial, we calculated holding velocity as the average velocity of those positions. In previous studies, holding velocity has been termed focal-point velocity (Grossman, 2014;Grossman et al, 2002) and is the optimal velocity predicted by the Grossman et al (2002) (Neuswanger et al, 2016) to calculate the elapsed time and distance between those two points. The strong linear relationship and high correlation between prey capture velocities and treatment velocities (R 2 = 0.97, y = 0.89x + 3.47) is evidence that our treatment velocities delivered prey at the desired velocity throughout the duration of trials.…”

“…Reactive distance represented the distance between the nose of a foraging drift feeder and a prey item when the fish first oriented towards the prey to initiate pursuit and capture. We estimated reactive distance using VidSync (Neuswanger et al, 2016), which calculated the distance between the prey item and nose of the experimental specimen at the moment of fish orientation towards the prey. Reactive distance was measured in three dimensions, with the theoretical maximum reactive distance being the diagonal through the test chamber (i.e., from low, near, rear corner to high, far, front corner).…”

Crossing boundaries: Shigeru Nakano's enduring legacy for ecology

“…New imaging systems and software are providing more accurate measurements of fish positions (Vivancos and Closs 2015;Neuswanger et al 2016), but Nakano's papers are still the standard for defining the principles of how salmonid behavior creates the dominance hierarchies that are ubiquitous in natural streams.…”

The Need and Use of Open Educational Resources in Fisheries, Environmental Education, and Conservation

“…For more detailed video research projects, a three‐dimensional video analysis program (Apple operating system) is available at http://www.vidsync.org (Neuswanger et al. ). Some guidance regarding videography and analysis is provided by Derry et al.…”