Sucker Migration Harbinger of Climate Change

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August 4, 2011

By Carolyn Rumery Betz

How do birds know when to fly south in the winter? How do fish know when to migrate upstream to spawn? The relationship between periodic biological phenomenon and climate, known as phenology, is taking on a new dimension these days.

While environmental triggers like the number of daylight hours remain steady, Wisconsin’s climate is changing.  Migration patterns of birds and fish may change in response to the warmer nights and winters, increased springtime precipitation, and more frequent intense rain events that Wisconsin is experiencing.

Peter McIntyre, a new faculty member at the University of Wisconsin-Madison, and his doctoral student Evan Childress are using funds from Wisconsin’s Water Resources Institute to better understand how climate change is altering fish migration patterns in streams that flow to the Great Lakes. McIntyre and Childress are particularly interested in learning whether it is flow or temperature that provides the cues to fish that it’s time to spawn.

Suckers, an important food source for large sport fish, usually start to move when the days are warm and the water is clear but before the trees have leafed out. The eggs and excrement they deposit as they move upstream serve as an important source of nutrients that fertilize the growth of the plants and insects living in spawning streams. If peak migration of suckers shifts, their interactions with migrating  sturgeon, pike, walleye and redhorse would also be affected.  In fact, changing the timing of the nutrient inputs from suckers could alter the dynamics of the entire stream ecosystem.

McIntyre and Childress, based at the Center for Limnology, are also collaborating with the U.S. Geological Survey and the Wisconsin Department of Natural Resources (DNR) to understand future stream flows under various climate change scenarios. Putting together detailed data on the fish migrations with the latest climate forecasts will allow them to forecast migration patterns under predicted climate conditions, including the fact that Great Lakes water temperatures appear to be changing faster than air temperatures.

Childress is engaging the public with his research by tapping into a network of citizen volunteers on 22 tributaries to Lake Michigan. The DNR/UW-Extension’s Water Action Volunteers devote about 15 minutes at a consistent time each day for three to five weeks looking for suckers to move upstream. The purposeful watching and documenting of the suckers’ arrival is awe-inspiring, according to Childress. The whole bottom of a little stream may be chock-full of fish.

Coggin Heeringa, is one such citizen scientist based at Crossroads at Big Creek, a 115-acre nature preserve in Sturgeon Bay. She used school groups, scouts and weekend visitors to count fish and take other water measurements.

“Suckers are an easy sell,” said Heeringa. “One second-grader told me that the sucker run is better than fireworks.”  She hopes to take part in the monitoring again in 2012 during the second year of the project.

Using citizen volunteers to document local changes may help more people understand that climate change is a local issue.

“We’re downscaling climate change to their backyard,” Childress said. “Understanding that in my local stream, the fish are going to be affected by climate change–that is huge.”

McIntyre noted that work with citizen volunteers has mutual benefits. “We could not collect data from so many places by ourselves, so our volunteers are essential contributors to the research effort as well as new ambassadors for native migratory fishes.”