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Great Lakes Article:

Eurasian Ruffe May Increase Pressure on Lake Michigan Yellow Perch

12/26/2002


WASHINGTON DC -
Eurasian ruffe, an invasive fish whose numbers have multiplied dramatically in Lake Superior, have now been spotted in northern parts of Lake Michigan. The good news is that round gobies, which are already abundant in Lake Michigan, may keep ruffe numbers down. The bad news is that Eurasian ruffe will nonetheless deplete resources for yellow perch, an important native sport fish.

With funding from Illinois-Indiana Sea Grant, Gary Lamberti, University of Notre Dame, and Martin Berg of Loyola (Ill.) University have been studying the relationship among Eurasian ruffe, round gobies and zebra mussels, and how this "exotic triad" can affect yellow perch. "Exotic species now dominate the food webs of the Great Lakes, including Lake Michigan," says Lamberti.

The researchers found that although the relationship between these invaders is complex, one fact is simple. The successful species is often the one that gets there first, noting that in Lake Superior Eurasian ruffe have become the dominant fish, while in Lake Michigan, round gobies have become numerically dominant, relegating ruffe to deeper waters.

Yellow perch in Lake Michigan are pressured early in life by competition from zebra mussels and round gobies. Zebra mussels filter plankton that larval perch need to grow. Gobies not only eat yellow perch eggs, they also compete with young perch for invertebrate food. Even a diminished ruffe presence will further impact the young perch.

As yellow perch grow larger they move to deeper waters, as do ruffe. Unlike larger yellow perch, ruffe prefer the bottom habitat, but nonetheless the two species will continue to tap the same food sources.

"The addition of Eurasian ruffe to Lake Michigan waters will likely increase the bottleneck on yellow perch," said Lamberti. "The native fish will experience increased competition during several stages of its life."

Contact: Gary Lamberti, Illinois-Indiana Sea Grant Researcher, Associate Professor of Biology, University of Notre Dame; Phone: (574) 631-8075; E-mail: Lamberti.1@nd.edu
Martin Berg, Illinois-Indiana Sea Grant Researcher, Assistant Professor of Biology, Loyola (Ill.) University; Phone: (773) 508-8853; E-mail: mberg@luc.edu

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