Why this matters:

• Invasive sea lampreys prey on most species of large Great Lakes fish such as lake trout, brown trout, lake sturgeon, lake whitefish, ciscoes, burbot, walleye and catfish. These species are crucial to Great Lakes ecosystems and to the region’s fishing industry.
• Understanding how sea lampreys migrate can inform management and conservation strategies, such as developing methods to catch the invasive fish that don’t involve dams, which reduce river connectivity, or lampricide, a pesticide that some communities and groups prefer not to use.
• The Great Lakes fishing industry is worth $7 billion and provides 75,000 jobs to the region. Reducing the amount of sea lamprey in waters is crucial for the industry’s well-being and the economic vitality of the Great Lakes.

How do you catch an invasive fish that’s solitary, nocturnal and doesn't feed on bait?

Invasive sea lampreys attack many large Great Lakes fish, like lake trout, sturgeon, and walleye, which are important to the ecosystem and fishing industry.

Researchers in the Michigan State University College of Agriculture and Natural Resources are one step closer to figuring it out.

In a study published in the Journal of Experimental Biology and funded by the Great Lakes Fishery Commission, Kandace Griffin, a fisheries and wildlife doctoral student, and Michael Wagner,  professor in the MSU Department of Fisheries and Wildlife, found that sea lampreys — a parasitic fish considered an invasive species in the Great Lakes region of the U.S. — follow a clear pattern of staying in the deepest parts of a river.

These findings are important for informing sea lamprey management strategies, conservation of fish species native to the Great Lakes and protecting the region’s $7 billion fishing industry and the 75,000 jobs it provides.

“We wanted to know how sea lampreys are making their movement decisions when migrating,” Griffin said. “Are they guided by certain environmental cues? Are they moving through areas that are safer? How can we potentially exploit those decisions or maybe manipulate them into going somewhere that they don’t want to go, like pushing them into a trap.”

MSU doctoral student Kandace Griffin releasing tagged sea lamprey into the river to monitor their movement paths through the White River in Whitehall, Michigan.

The primary methods used to control sea lamprey are dams that block them from entering waterways and lampricide, a species-specific pesticide that targets lamprey larvae.

“Dams create a lot of challenges for conserving river ecosystems: They block all the other fish that are moving up and down in the system. Even though lampricide is proven to be safe and effective, there are communities that are uncomfortable with its use going into the future,” Wagner said. “Figuring out the right way to fish sea lamprey would decrease its population, lower reproduction rates and provide managers with the opportunity to match their control tactics to the community’s needs.”

To track lamprey movements, Griffin and Wagner used a method called acoustic telemetry, which involved using sound emitted from a surgically implanted tag to track the movement of 56 sea lampreys in the White River near Whitehall, Michigan.

Griffin likened acoustic telemetry to GPS.

“There’s a tag that emits sound and has a unique transmission with a unique identification code, so I know exactly which fish is going where,” she said. “The receivers are listening for that sound and then calculating the time it reaches each receiver. We used this information to triangulate the position of the sea lamprey and analyzed it to find out how they’re using the river’s environmental traits to make decisions on where to swim.”

Getting acoustic telemetry receivers ready to go in the water. Each receiver is tied to a metal rod that is pushed into the river bottom so it can pick up signals from tagged sea lampreys swimming by.

Of the 56 lampreys studied, 26 of them (46%), consistently chose the deepest quarter of the river.

“For nearly 20 years we have been discovering how sea lampreys migrate along coasts and through rivers. Now, thanks to Kandace’s work, we know where their movement paths come together near a riverbank — the perfect place to install a trap or other fishing device,” Wagner said. “That knowledge can be used to find similar sites across the Great Lakes basin.”

Right now, a fishing device designed to catch bottom-swimming, solitary, nonfeeding, nocturnal sea lamprey doesn’t exist.

However, Wagner notes there are places around the world — including Indigenous communities in the U.S. — where people have fished migratory lampreys of various species for hundreds of years and could help inform the creation of such a mechanism.

Field technician Ceridwyn Hunter, a MSU alum, tending acoustic telemetry receivers used to track sea lamprey through the river.

“We have recently had a proposal funded to scour the Earth in search of knowledge, both scientific and traditional, about how to capture migrating lampreys and similar fishes,” Wagner said. “We want to talk with the communities of people who have histories fishing these animals and use this information, along with other data we’ve gathered, to conceive a device that could be used to fish sea lampreys.”

Griffin views the new intel on lamprey migration patterns as a way to inform fishing practices to complement some of the existing control methods.

“Hopefully, we can use this as a supplemental control method to the use of the barriers or dams,” she said. “We have societal pressure to remove barriers to enhance river connectivity, and some barriers are failing. Open water trapping is another way that we could try to still combat the invasive sea lamprey problem here but also promote river connectivity and other conservation goals for other species.”

Wagner shares the same perspective.

“When a community, or the Great Lakes Fishery Commission, or the governments of Canada and the U.S. come in and say, ‘We’d really rather be able to control this river with something other than lampricide,’ we want to be able to be able to provide 360-degree solutions that specify where to fish, when to fish and how to fish using fully prototyped and tested equipment,” he said. “We want our science to help solve real-world problems.”