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.

Summer 2022 project update

It’s been a crazy summer for our lab with multiple projects getting off the ground. One of the big ones of course was this fish tracking project on Ston(e)y.

We got onto the water at the end of May, about a week after the big storm hit. We owe a huge thanks to Brent Whetung for providing temporary boat and equipment storage on the lake, and the use of his boat launch. We spent early June deploying the array of 60 underwater acoustic telemetry receivers (the fish ‘listening stations’), which provide full coverage of Stoney and Upper Stoney, and extend part of the way down into Clear Lake. It was kind of a nice time to be on the lake, because we mostly had it to ourselves – is was very quiet other than the distant sounds of chainsaws. The first week we were there, the hydro crews were all over the lake.

Some pictures and video clips of receiver deployment work are below. The receivers are suspended off the bottom, but everything including the floats is at least six feet below the surface. These receivers will be able to detect our tagged fish if they swim within ~500m of a receiver, although detection ranges can vary a lot depending on conditions – it is not uncommon with this technology for fish to be picked up from 1-2 km away. The fish are sending out their signals every 2 minutes, so they only have to swim within range of the receiver for 10-20 minutes and we have a good chance of detecting them. When we pull up the receivers next spring for downloads and battery changes, we’ll start to get a sense of the behaviour and habitat use of the fish in the system.

Speaking of fish, we also got started on tagging a few fish in June but were cut off by the water temperatures getting too warm. In total we tagged 18 fish – a mixture of walleye (pickerel), yellow perch, and smallmouth bass (pictures below). Warm water temperatures are bad news for fish health and survival when it comes to catch-and-release, although the effects of temperature vary a lot among species. Because the tags (transmitters) are expensive, and because the 3-min surgery adds extra stress, we are focusing our tagging on when water temperatures are cool to ensure fish recover quickly and go on to live for a long time. The tags we’re putting in these fish will last for 3 years in the case of the larger animals, and about 1 year for the mini tags we’re putting into perch. If tagged fish are harvested, the tags can be returned to us a re-used (tagged fish are safe to eat).

We plan to be back out in early fall to do some more tagging, and expect spring 2023 to be our big tagging effort where we’ll get the rest of our tags out. We’re still in need of funding to purchase more transmitters for 2023 so we can keep the project going, if you’re interested in donating please follow this link! https://mycommunity.trentu.ca/tarpgive

And get in touch with me if you have questions.

Graham

Video (above) showing the team lowering an acoustic receiver (the cylindrical black thing) into the lake on a calm day in early May, near Ship Island. The big orange float sits 6-10 feet below the surface, and keeps the receiver off the bottom, listening for tagged fish to swim by.

Photo (above) showing underwater shot taken from a DFO underwater drone (that's its claw you can see), looking down at one of our receivers. This receiver setup is designed for shallow areas, where the receiver sits inside a white PVC tube that is embedded into the concrete anchor. A small yellow float suspended off the anchor helps us spot the receiver.

The photos above show (top) Dr. Brownscombe and his assistant Amanda doing surgery on a walleye in Stoney Lake. The fish (sutured incision shown in 2nd photo) is now swimming around the lake, being tracked by our receivers.

Photo (above) of Dr. Raby with a smallmouth bass in Upper Stoney, ready to be released moments after being surgically implanted with a 3-year acoustic transmitter. This and the other fish that have been tagged so far were all caught by angling.

Introducing the Stoney Lake Fish Tracking Project

The project

At Trent University, we are preparing to build a long-term research program focused on the health of the Stoney Lake ecosystem. The goal of this program is to conduct world-class research on Ston(e)y Lake, Clear Lake, and Upper Stoney (referred to as Stoney Lake hereafter), in close partnership with the people and organizations who are already doing important environmental work on these lakes. To begin the program, we will conduct a multi-year fish tracking project that will answer questions about fish behaviour, spawning, survival, habitat needs, and the effects of changing water quality. This fish tracking project is the starting point for a longer-term program that will include research on the full range of threats that impact the Kawartha Lakes (e.g., invasive species, toxic algae, climate change). Healthy lakes depend on a complex balance of the biological community, including numerous organisms such as plants, insects, and fish.

How it will happen

This is a community-driven project, made by possible by in-kind support and generous donations by community members, led by the Ingleton and Szego families of Stoney Lake who have donated the necessary funds to start the program, and who will continue their support in the years to come and assist with bringing other donors on board. We also have an exceptional partner in Dr. Jake Brownscombe from Fisheries and Oceans Canada (DFO), who will provide a major investment of time, expertise, and equipment that makes the project possible. We will also work with other government agencies and the local people and organizations who are already doing important ecosystem monitoring.

The project will involve multiple fish species but will focus particularly on walleye (often referred to as ‘pickerel’ in Ontario), an important fishery species that has declined in the Kawarthas. Acoustic telemetry will be used to track the movements of fish, by listening for ‘tagged’ fish (fish implanted with acoustic transmitters) with a network of underwater ‘listening stations’ (acoustic receivers). The transmitters will transmit their signal every ~3 minutes to receivers and will last for 3-4 years, allowing us to follow the lives of individual fish over time. Fish tracking will be complemented by monitoring of key habitat variables like water temperature, clarity, and dissolved oxygen. We are planning on getting started this spring (2022).

An acoustic receiver (the black cylinder suspended on the rope) deployed underwater in Lake Huron, similar to how they for the Stoney Lake fish tracking project. The receivers and floats will be below the surface, out of sight, and a minimum of 6-feet below the surface so they do not interfere with navigation. Photo credit: Tom Binder.

So what?

The fish tracking project will reveal fascinating and previously unseen fish behaviours in ways that will help engage the community in thinking about the lake as a living system. We will gather valuable information on where and when fish spawn, estimate their survival rates, identify crucial summer foraging and over-wintering areas, and help understand the impacts of threats like changing water quality.

Support the next generation of freshwater biologists

Future updates will celebrate the achievements of the undergraduate and graduate students at Trent helping to carry out this research. The research will produce valuable insights but also help train the next generation of freshwater biologists who, in the process, will become deeply engaged with the Stoney Lake ecosystem and surrounding community.

The program would benefit greatly from additional donations to support the personnel costs (undergraduate and graduate students at Trent University) to run the fish tracking project over the coming years, and to fund the purchase of acoustic transmitters (tags to track fish). If you are interested in donating, please get in touch with Emily Vassiliadis (emilyvassiliadis@trentu.ca) at the Trent University Advancement Office.

Stay tuned

We are excited for this project to begin and to connect with the community. Stay tuned to this blog page for project updates.

A walleye being released in Lake Erie after having an acoustic transmitter inserted into its body cavity. The fish is also externally marked with an orange numbered so that it can be easily identified when recaptured in the fishery tag (we will likely use slightly different tag types for Stoney Lake fish). Photo credit: Andrew Muir.