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Exploring the use of underwater video for fish monitoring in the Kawarthas

By Jacob Bowman, undergraduate research technician in the Raby Lab

As many local anglers know, Stoney Lake is home to a diverse assemblage of fish species. One important habitat for fish is the nearshore zone where light can easily penetrate, and plants grow in abundance to provide cover. As ecologists, we are interested in how fish relate to conditions in the nearshore habitat. One plant, the invasive starry stonewort (Nitellopsis obtusa) is of particular interest because it is spreading rapidly in Stoney Lake and the Kawarthas, and there is concern that it may negatively impact native organisms. We are investigating this concern by using Remote Underwater Video Systems (RUVS), while more broadly exploring whether RUVS might be useful for long-term monitoring of nearshore fish communities in the Kawartha Lakes. We are starting the project by focusing on Stoney Lake and the Otonabee River (around Trent U). My work on this project in 2022 was made possible by a donation from Ralph and Carol Ingleton.

What are RUVS?

RUVS are underwater camera stations that are deployed to film aquatic animals in their natural habitat. We are using videos from RUVS to count the number of fish species at a site and to estimate the number of individual fish there. Our RUVS setup consists of a GoPro camera attached to a cement base with a rope and small buoy. There is also a sighter arm that gives us a sense of how far we can see (the size of the visual field). RUVS are commonly used in studies of marine animals and are starting to be used more frequently in freshwater. RUVS have a few advantages when compared to the usual fisheries monitoring techniques like netting. They can be used by inexperienced researchers like students, volunteers, and community members, because very little training is required. Other types of fish monitoring that involve capturing fish may cause fish to be stressed or injured. RUVS on the other hand have little or no direct impact on fish, and don’t require a scientific collection permit.

RUVS in Stoney Lake

This summer we have been deploying RUVS at sample sites across the nearshore waters of Upper Stoney Lake. At each sample site we measure water temperature and clarity. We then deploy a RUVS and record a one-hour video. A big job for the winter will be reviewing the videos to count the fish and identify the plant species at each site. In the videos we have reviewed so-far, we have identified 11 fish species. The most common fish species in our videos so far have been pumpkinseed and bluegill sunfish. Some other fishes we have observed include golden shiner, brown bullhead, black crappie, and juvenile walleye. In addition to fish and plants, we were surprised that we also filmed a pair of otters checking out our camera at one site (scroll down for the video). RUVS could be potentially used to monitor the presence and abundance of many underwater animals like otters, invertebrates, or turtles.

Our hope with this project is that RUVS can be as a long-term option for the Stoney Lake community to monitor the nearshore fish assemblage, supplementing the fisheries monitoring work that is done by the Ontario MNRF every five years (using gillnets). Long term monitoring is essential for detecting environmental change. For example, as new invasive species enter Stoney Lake, a long term RUVS study could be used to quantify their impacts on the ecosystem and better understand why they're spreading.

Video (above): RUV footage from Upper Stoney Lake, with a pair of otters scaring away all the fish in sight.

Video (above) shows a curious smallmouth bass (Upper Stoney Lake) checking out or RUV setup.

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