Editor’s note: This article was written by 2023 summer undergraduate intern Hadley Vande Vusse
Hi! My name is Hadley Vande Vusse, and I am a senior at the University of Michigan. I am majoring in Earth and Environmental Sciences, as well as Sustainability with a minor in Oceanography. Over the past three months, I have been conducting research, with the Michigan Department of Natural Resources (MDNR), on the movement ecology of lake trout in Northern Lake Michigan using acoustic telemetry.
The movement of lake trout in Lake Michigan
In a continuously changing world, understanding the movement of fish in the Great Lakes is essential to the survival and preservation of fish populations (Cooke et al.,2022; Verhelst et al., 2023). Additionally, understanding the movement of a species with such a high social and economic value, like the lake trout, is important, because it can tell us the distribution, abundance, dynamics, persistence, and ecological community structure (Bi et al., 2020; Nathan et al., 2008). Lake trout are apex predators that live in the vast waters of Lake Michigan and can be found in all five Great Lakes. They are known to spawn on rocky reefs and occupy the cold, deep waters of Lake Michigan.
Why lake trout?
In Lake Michigan, lake trout are subjects of intense fisheries management due to their near extirpation and are significant to both tribal commercial fisheries and recreational fishing. Their dangerously low numbers were due to the basin-wide collapse in the mid-1900s, as a result of expanding commercial fisheries, invasion of sea lamprey, habitat destruction, and contamination (Muir et al., 2012; Cline et al., 2013). Successful management efforts to reduce fishing mortality, mitigate habitat loss and changes to native food webs, control non-native species invasions, and conserve fish stocks, have led to the rehabilitation of Great Lakes lake trout populations (Muir et al., 2012). Nonetheless, rehabilitation efforts have not entirely re-established a self-sustaining lake trout population. Due to the population’s reliance on stocking, we must understand their movement patterns to help create a sustainable wild population.
How can we track their movements?
Acoustic telemetry is becoming a standard method to broadly investigate the behavior, habitat preferences, and population dynamics of fish. Acoustic telemetry is an aquatic tracking method that uses internal tags to transmit unique acoustic signals, which are then detected by receivers under the water. These detections log GPS coordinates and take depth and temperature measurements.
How did I contribute to understanding the movement of lake trout?
I studied thirty-five tagged lake trout in northern Lake Michigan. These fish were tagged in October and November 2021 (spawning season) in Good Harbor Reef off the coast of Leland. I used R (programming language) to analyze distance, location, temperature, and depth data. Location data revealed that the tagged lake trout moved in several directions after spawning. Some moved north or south, while others swam into the Grand Traverse Bay or stayed on the reef. These fish have the ability to travel large distances and do it all in a matter of months. The variation in movement patterns and location may suggest that lake trout can adapt their movement patterns to environmental changes, but more research must be done to prove this.
It is necessary to gather more information about the movement ecology of lake trout for effective fisheries management. If we know what habitat fish like to occupy and how they traverse across areas, we can implement appropriate harvest limits, refuge boundaries, and much more!
I was able to go out with Ben Turschak (MDNR Biologist) and a USGS crew to observe the surgical implantation of the tags in whitefish, another important species to the Great Lakes. I helped take routine measurements, such as total length and a fin sample, and observed the fish’s behavior after surgery to make sure it was healthy enough to release.
This summer, I also participated in the Lakewide Assessment Plan (LWAP) with the MDNR. LWAP is a survey that has provided MDNR with a comprehensive understanding of the status of adult Lake Michigan fish populations through a multispecies focus. Want to learn more? Check out A Day on the Steelhead blog, by Ava Tackabury and me!
Recently I joined another MDNR crew partnered with the Little Traverse Bay Bands of Odawa Indians and Michigan State University to survey the juvenile lake sturgeon population in Black Lake. The assessment was conducted to determine the status of juvenile lake sturgeon and the success of stocking efforts (MDNR).
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Cline, T. J., Bennington, V., & Kitchell, J. F. (2013). Climate change expands the spatial extent and duration of preferred thermal habitat for Lake Superior fishes. PLoS ONE, 8(4). https://doi.org/10.1371/journal.pone.0062279
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