Inland Lake Sightings: A Tale of Two States

From January, 1996 (Update #26)

Michigan inland lakes are becoming more rapidly colonized than Wisconsin lakes, according to the results of a cooperative project supervised by Ladd Johnson (Universite Laval) and Clifford Kraft (University of Wisconsin-Madison), with assistance from many cooperating individuals and agencies. The comparison showed a different pattern developing in each state. By the end of 1995, adult or larval zebra mussels had been confirmed in 33 inland Michigan lakes, five more than at the end of the previous year. Adult zebra mussels had been confirmed in 21 Michigan lakes; veligers had been detected in the other 12 lakes. Unconfirmed adult sightings had also been reported from an additional five inland lakes. Wisconsin sightings have been scarcer than in Michigan. Adult or larval zebra mussels had been detected in seven inland Wisconsin lakes by the end of 1995, three of which were new sightings. In total, four Wisconsin lakes had confirmed adult populations; the other three lakes had veligers. No unconfirmed adult sightings have been reported from Wisconsin lakes. It is unlikely that the observed differences in inland lake sightings are due to sampling differences because the sampling efforts were similar in both states. Rather, Johnson and Kraft speculate that the abundance of submerged macrophytes in source waters may be responsible for the different pattern in each state. In earlier work, Johnson noted that submerged macrophytes with attached zebra mussels were often found hanging on boats and trailers being removed from zebra mussel-infested Lake St. Clair. The abundant macrophyte growth in Lake St. Clair could have contributed to the rapid spread of mussels to inland Michigan lakes. To date, Lake Michigan, which is relatively free of macrophytes, has been Wisconsin's primary zebra mussel source. Unfortunately, this could change now that several macrophyte-rich inland Wisconsin lakes are infested and have become potential sources for further inland lake colonizations.

ID: 199601-1.

The Zebra Mussel Update was a 4- to 8-page quarterly national newsletter published by the University of Wisconsin Sea Grant Institute from May 1990 through May 1997. The ZMU documented the spread of the zebra mussel -- an exotic nuisance mussel -- through North America's freshwater environments, especially the Great Lakes, and on efforts to control it.