June 7, 2004
Young Yellow Perch Like Rocky Bottoms!
Ann Arbor, Mich. — When Lake Michigan yellow perch and alewife are looking for their first home, they apparently prefer floors made of rock rather than sand.
In the past, researchers have tended to sample for young fish in areas where there is lots of sand simply because these areas are more easily sampled. However, sampling on sand has yielded very few young yellow perch, and this was cause for concern.
"Yellow perch have been in a serious decline in Lake Michigan for about fifteen years", says John Janssen, a Senior Scientist at the University of Wisconsin-Milwaukee. "When fish populations get into trouble, it's often the case that the trouble affects the youngest individuals. We need to know where these young fish live and how they get there."
The young fish emerge from eggs and drift around for at least six weeks before settling down. They may have drifted a hundred miles, but they seem to wait until they are above rocky substrates before they actively choose to stay around. Indeed Janssen and Michelle Luebke have, at times, collected more young yellow perch in one sample over rocky substrate than the combined annual total for all the Lake Michigan biologists that sample sandy areas! Young yellow perch, 2-3 inches long, were about four times as abundant on rocky substrate compared to sandy substrate, and their diet was mainly small invertebrates that live among the rocks.
Original Publication Information
Results of this study, "Preference for rocky habitat by age-0 yellow perch and alewives," are reported by John Janssen and Michelle Luebke in the latest issue (Volume 30, No 1, pp. 93-99) of the Journal of Great Lakes Research, published by the International Association for Great Lakes Research, 2004.
Contacts
For more information about the study, contact John Janssen, Great Lakes WATER Institute, University of Wisconsin-Milwaukee, Milwaukee, WI 53204, jjanssen@uwm.edu, 414-382-1733.
For information about the Journal of Great Lakes Research, contact Marlene Evans, Editor, National Water Research Institute, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada; marlene.evans@ec.gc.ca; (306) 975-5310.
Since 1967, IAGLR has served as the focal point for compiling and disseminating multidisciplinary knowledge on North America's Laurentian Great Lakes and other large lakes of the world and their watersheds. In part, IAGLR communicates this knowledge through publication of the Journal of Great Lakes Research, available to members in print and electronic form. A searchable archive of the journal is available online and includes the abstracts of articles from the journal's inception in 1975 through the most recent issue. In addition, complete articles are available to members who have signed up for an electronic subscription.
