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.firstname.lastname@example.org
Martin Berg, Illinois-Indiana Sea Grant Researcher,
Assistant Professor of Biology, Loyola (Ill.) University;
Phone: (773) 508-8853; E-mail: email@example.com