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Investigating Great Lakes Fish Migrations

Every spring, fishes known as suckers migrate from the open waters of the Great Lakes to their spawning streams. A Shedd researcher is working with an army of community scientists from Illinois to the Upper Peninsula to monitor these mass movements. The data will help us better understand the dynamics of—and challenges to—the migrations of these ecologically important fishes.

How to Help

Whitenose suckers have a long, tapered body with a small, pointed fin on their spine.
A Shedd researcher stands in a stream, writing down observations.

Why study suckers?

Of the more than 50 species of Great Lakes fishes that make spawning runs, white and longnose suckers (family Catostomidae) are especially well-suited for migratory studies: Both species are widespread, numerous and ecologically important, transferring nutrients between the Great Lakes and upland habitats. While the fishes are in their spawning tributaries, their eggs and waste products enrich the entire food web, from aquatic plants to predators. Suckers are also large and easy for volunteer observers to identify.

The challenges that suckers face in their migrations, including habitat fragmentation and climate change, are representative of what other native migratory fishes in the Great Lakes deal with. In addition, while they are common fishes, suckers have not been extensively studied, so data our research team compiles will also be useful for future conservation and management strategies for them.

““Suckers have an important ecological role to play because they’re making these early-spring mass migrations into the tributaries and contributing nutrients that kick-start the food web.”

Karen Murchie, Ph.D., Director of Freshwater Research
A winding river in a forest reflects the blue sky.

What can we learn?

In this multiyear project, Shedd's Director of Freshwater Research Karen Murchie is assessing data gathered through observations by trained community scientists, biotelemetry, blood chemistry and genetics. She is documenting the start, peak and end of the rolling wave of migrations along a gradient from the western shore of Lake Michigan up to the south shore of Lake Superior. Data loggers she places on the bottoms of the spawning streams record water temperatures and flow rates, information to help her determine what environmental cues initiate spawning migrations. And by comparing current migration timing to historical records, she is examining the local impacts of climate change on the Great Lakes.

Murchie is also tracking whether the fishes return to the same spawning sites every year and evaluating the physiological stresses on the suckers when they have to navigate migration barriers such as dams and culverts. The results of these studies will be used to inform future habitat restoration projects.

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