Our spring 2024 muskie tagging bonanza

By Amber Fedus, PhD candidate at Trent University

From April through early June, I worked with Kurt Smith from DFO, along with several volunteers from our lab, to tag some elusive muskie on Stoney Lake. Going into this field season, we had many tags that needed to be put into muskie. We had been concerned that we wouldn’t be able to tag as many fish as we wanted to, after having a tough time the last couple years trying to catch them. Despite our concerns, we ended up coming out of the spring tagging season with a total of 29 more muskies tagged! Special thanks to members of the Kawartha Lakes Chapter of Muskies Canada for coming out on muskie opener to assist with angling muskies to get our remaining tags out.

A sped-up video is below showing our tagging process. In total, we tagged 21 fish that were caught by lectrofishing (mostly in April) and eight that were caught by angling. In 2022 and 2023 combined, we had only tagged a total of eight muskies. Of the 29 muskies we tagged this spring, they ranged in size from 17 to 47 inches in length (average = 35 inches). We had a range of tag sizes available to suit the size of the fish.

Muskies Canada Inc. (MCI) awarded us a two-year research grant to support this project, and members of the Kawartha Lakes Chapter of MCI have also provided generous donations. Because of these donations, we were able to purchase sensor tags for the muskies, meaning that in addition to tracking their movements we’ll get information on acceleration (activity levels), depth, and body temperature. We’re going to be able to generate a lot of amazing insights into the diverse behavioural strategies muskies use, and help better understand their habitat needs.

Kurt recently led the downloading of our acoustic receivers, in addition to other sensors that record things like temperature, light levels, and oxygen. Those downloads mean we now have over 20 million detections of our tagged fish across the system. It’s a huge pile of data we’ll be able to use to answer questions about fish movement and habitat use over the next several years. We'll share some findings here soon.

In addition to tracking the behaviour and habitat use of fish, we’re doing as much as we can to collect other types of data to help explain how and why the fish are doing what they’re doing. To that end, I will be doing a lot more fieldwork this summer to sample smaller organisms, sediment, and algae from sites across the lake. These will be used to analyze chemical tracers (stable isotopes) to figure out what the fish we’ve tagged are eating, where they’re eating, and how energy is moving through the food web.

(Above) Photo of some of our field crew from this spring, including Jacob Bowman (left), Leah Howitt (middle), and myself (Amber, right). In the surgery trough is a muskellunge at the end of what is a brief (5 min) surgery, about to be released. The fish's gills are flushed with fresh lake water throughout the process.

Awash with data

In late June and early July, Kurt Smith (DFO research technician) and Dr. Jake Brownscombe (DFO research scientist) led the download of the 60 acoustic receivers we have deployed across Upper and Lower Stoney, and Clear Lake. The receivers are our 'listening stations' that have been in position since last summer, listening for our fish tagged with acoustic transmitters. Deploying, retrieving, and downloading receivers is the most labour intensive and technically challenging part of the field work for a project like this. Each receiver has to be hidden below the surface and anchored to the bottom. In our case, most receivers were suspended off the bottom with a float, in all sorts of depths and locations. Ranging from 100 feet of water in Upper Stoney to shallow, weedy areas that were only 8 feet deep.

Kurt and Jake have perfected a new way of retrieving the receivers, using ActiveTarget Live Sonar (a Lowrance toy) to visualize the receiver and float suspending it from the bottom. They then use an underwater drone with an arm and claw to hook a rope onto the anchor. Once that's done, a bit of (human) muscle on board the research vessel is used to pull the whole thing up off the bottom. To keep the receivers in place, we are using 85 lb concrete anchors that we made ourselves, so it's a good workout for Jake's team to pull those into the boat.

The good news: the receivers contained a huge amount of data (detections of our tagged fish). The bad news: the receivers contained a huge amount of data. Really, it's mostly good news that everything is working well, but the management and analysis of huge datasets are the key bottleneck with fish tracking projects. We're already at >5 million detections of our tagged fish from our network of receivers. The vast majority of fish we've tagged were only tagged recently and their tags will last years. Which means that when we go to download the receivers again next summer, I'm guessing we'll be north of 20 million lines of data. It's a good problem to have, and our team has the expertise needed. For the PhD student on the project, Amber Fedus, wrangling these data be a wonderful learning opportunity over the next few years.

(Above) Summary of number of fish tagged to date, number of detections of those fish, the number of unique animals detected so far on our receivers, and the number of unique stations on which each species has been detected. Note: the vast majority of the animals were only tagged a few weeks before the receivers were downloaded.

One fun (or not so fun) note from the receiver downloads: a couple of the receivers were completely covered in zebra mussels, after just one year in the water (see picture below). For some reason, these happened to be the ones in Clear Lake. There were zebra mussels on receivers elsewhere, but the Clear Lake ones had by far the heaviest coverage. If anyone reading this knows why that's the case, or has observed the same trend in this system, let me know. I've been asked whether a coating of mussels will prevent the receiver from 'hearing' the fish transmitters. The answer is no, but it might reduce the receiver's performance a bit (i.e., it might have slightly impaired hearing). Some folks working on Lake Erie are working to quantify how big of a problem zebra mussels are for receiver performance.

(Left) Image of an acoustic receiver, completely covered in zebra mussels after one year of deployment in Clear Lake. Inset is an imagine of what the receiver looked like a year ago. Photo courtesy of Kurt Smith.

Finally, on an unrelated note: thanks to Tricia Mason from Global News Peterborough for having Amber and I on their morning show last week to talk about this project. You can see our interview here. https://globalnews.ca/video/9904720/aquatic-research-program-providing-experiential-learning-for-trent-university-students/

Tag, You're It! 153 new fish join our tracking project

This spring, our team led by PhD student Amber Fedus, along with Dr. Jake Brownscombe and Kurt Smith from DFO, worked long days over many weeks to put a whopping 153 new transmitters into fish on Stoney Lake. We are now up to 215 fish (!!) that have been implanted with transmitters. The overall tally includes 79 walleye, 69 smallmouth bass, 36 yellow perch, 23 black crappie, and 8 muskellunge. It was a huge team effort; nearly every member of the Raby Lab spent time in the field helping Amber, Jake, and Kurt. Special thanks to Brent Whetung for catching walleye for us, to Ben and Viamede Resort for use of their docks, and to Ed Paleczny and Jackie Ouellette who also let us use their property.

(Left) The research team from this spring.

The tagging season wasn’t without its challenges. Many long days and nights of angling and electrofishing, often to catch very few of our target species. A heatwave in May surged water temperatures, not an ideal condition for fish survival. We adapted by tagging the fish at night when it was cooler, using cold water pumped from deep.

We notably struggled to locate muskies, known as the 'fish of 10,000 casts'. Nevertheless, we tagged six more, taking our total to eight. Muskies Canada Inc. and the Kawartha Lakes Chapter have generously contributed a combined $6500 for purchasing transmitters. They also arranged a muskie fishing day for us (to catch fish for tagging), which, due to the heatwave, had to be canceled to avoid risk to the muskies. We plan to reschedule it for October, with the help of volunteer anglers and will further aim to catch more muskies next spring during their spawning period.

A couple of individuals have reported finding tagged fish – an encouraging sign. The walleye bear a conspicuous external loop tag on their back (see video), marked with my contact number and a unique ID. Other species don't have external tags, but a recent tagging will reveal an incision site on their underside. The tagged fish are safe to consume and if a transmitter is returned, we can repurpose it for another fish. If you come across someone unsure about what to do with a tagged fish, don't hesitate to direct them to me at grahamraby@trentu.ca.

This week, we've begun extracting underwater receivers to gather fish detection data, a process that will span a couple weeks. After a quick battery change, we re-deploy the receivers in their original spots, concealed 6+ feet below the surface. We'll then start the demanding task of organizing millions of data points and beginning to decipher the activities of our aquatic subjects. Keep an eye on this space for more updates!