On a crisp spring morning along the shores of Lake Erie, a team of biologists load equipment onto a research boat. These biologists are from the U.S. Fish and Wildlife Service's Lower Great Lakes Fish and Wildlife Conservation Office (FWCO) and New York State Department of Conservation (NYSDEC) Lake Erie Unit. But there鈥檚 no fishing gear on board鈥搉o nets, no rods, no reels鈥搒till, they鈥檙e fishing. Their mission? To find lake trout and cisco fitted with tiny transmitters, swimming unseen in the depths of one of North America鈥檚 most storied lakes.
The scientists are part of a new collaboration to answer a question that has long vexed fisheries managers: What happens to hatchery-raised fish after they鈥檙e released into the wild?
Caption: Biologists from the USFWS Lower Great Lakes Fish and Wildlife Conservation Office and New York Department of Conservation set out from Dunkirk Harbor on a crisp April morning to deploy acoustic receivers that will help unravel the movements and survival of hatchery-raised fish in Lake Erie. (Photo credit: Collin Farrell/ USFWS)
Using acoustic telemetry, a technique that relies on underwater receivers to track the movements of tagged fish, the team is monitoring survival after stocking and the movement of these two native fishes. With an array of 100 receivers spaced two kilometers apart across Lake Erie鈥檚 eastern basin, it鈥檚 one of the most ambitious tracking projects of its kind on the lake. 鈥淓ach time a fish swims within range of a receiver, we log its presence. Over time, that data paints a picture of survival, behavior, and habitat use鈥� says Dimitry Gorsky, a fish biologist with the Lower Great Lakes FWCO native species program.
What makes it even more powerful is how it鈥檚 being integrated into the Great Lakes Acoustic Telemetry Observation System (), a basin-wide collaborative network of over 2,000 receivers that typically span larger distances.
鈥淕LATOS gives us the broader picture-regional movements, basin-scale migrations,鈥� said Gorsky. 鈥淏ut by layering in our denser array, we get much finer detail on what鈥檚 happening right after fish are released. It鈥檚 like zooming in from a satellite view to a street-level camera.鈥�
This integration means researchers can track fish from the moment they are stocked through their earliest days, and鈥搃f they persist鈥揵eyond, as they move throughout the array and GLATOS-covered waters across the Great lakes. The result is a seamless fusion of fine- and broad-scale telemetry, offering insights into both local behavior and lake-wide connectivity.
Caption: The dense eastern Lake Erie acoustic telemetry array (black) complements the broader GLATOS network (white), providing fine-scale tracking of post-stocking behavior alongside basin-wide fish movement data. (Created in ArcGIS Pro by: Collin Farrell/USFWS)
A new chapter in an old story
This project is part of a broader Great Lakes effort. Green Bay and Alpena FWCOs are conducting parallel studies in Lake Michigan and Lake Huron, each focused on improving the success of hatchery stocking programs that are critical to native fish restoration.
Lake trout and cisco were once ecological "linchpins" of the Great Lakes, dominant predators and prey that helped to maintain balance in the food web. But overfishing, habitat degradation, and the introduction of invasive species invasive species
An invasive species is any plant or animal that has spread or been introduced into a new area where they are, or could, cause harm to the environment, economy, or human, animal, or plant health. Their unwelcome presence can destroy ecosystems and cost millions of dollars.
Learn more about invasive species like sea lamprey and alewife devastated their populations by the mid-20th century. In response, government agencies turned to hatcheries to help fill the gap. Millions of lake trout and cisco have been stocked throughout the Great Lakes in the decades since their collapse, and with mixed success. While some populations have shown signs of recovery, others remain stubbornly slow, and scientists have struggled to understand why.
鈥淥ne of the biggest blind spots has always been what happens after release鈥� said Brian Layton, a fish biologist at Allegheny National Fish Hatchery and project collaborator. 鈥淒o they survive the first few days? Do they stay in the area? Are they getting eaten? Acoustic telemetry gives us a way to finally start answering those questions.鈥�
Photo caption: Hatchery-raised lake trout being stocked into Lake Erie to help rebuild native populations. (Photo credit: Collin Farrell/USFWS)
Science that hits home
The work being done here isn鈥檛 just academic. Lake Erie supports one of the most valuable freshwater fisheries in the world, generating hundreds of millions of dollars annually through commercial and recreational fishing. In New York, the lake is a cornerstone of the local economy and source of cultural identity for lakeshore communities. 鈥淥ur goal is to support sustainable, self-reproducing fish populations鈥� said Gorsky. 鈥淲hen that happens, everybody wins鈥揺cosystems are healthier, agencies can reduce stocking costs, and anglers benefit from better fishing opportunities.鈥�
In addition to guiding hatchery operations, the data collected through this project will feed into regional population models and help state partners like the NYSDEC design more effective sampling programs.
Listening to the Lake
Roughly the size of a thermos, acoustic receivers rest silently on the lake bottom, waiting for passing fish to 鈥減ing鈥� them. The transmitters implanted in the fish emit unique acoustic signals every few minutes. By analyzing the patterns of detections over time and space, scientists can infer survival rates, habitat preferences, and even how they interact with other species or environmental conditions.
The Lower Great Lakes FWCO and NYSDEC team implanted acoustic transmitters in 80 lake trout and 70 cisco in late April, 2025. Following a two-week recovery period, the tagged fish were stocked into Lake Erie in early May alongside approximately 70,000 others of the same species. This marks the first ever large-scale cisco stocking event in Lake Erie, apart from a prior experimental release of 100 fish. The team expects to begin collecting early data on survival and movement patterns later this summer when they are doing array maintenance. Since the tags have an expected battery life of about one-year, new fish will be tagged annually to build a robust, multi-year dataset. Ultimately, the study could change not only how hatchery fish are stocked, but also how scientists evaluate the long-term success of recovery programs.
Caption: Illustration of a tagged lake trout 鈥減inging鈥� an acoustic receiver sitting on the bottom of a lake. (Art credit: Matthew Nguyen)
鈥淚t鈥檚 a long game,鈥� said Gorsky. 鈥淲e鈥檙e building on the foundation for science-based management decisions that can help restore balance in these lakes.鈥�
And in the cold blue depths of Lake Erie, where so many questions have gone unanswered for so long, that work begins with a simple signal: one fish, one ping, one clue at a time.
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