Summer Sightings

From September, 1994 (update #22)

Zebra mussels made their first significant move into Wisconsin inland lakes this summer. Adult mussels were found in Elkhart Lake in Sheboygan County and Racine Quarry in Racine County; veligers were discovered in a plankton sample from Okauchee Lake in Waukesha County. Subsequent surveys failed to turn up adult mussels in Okauchee Lake. No veligers were detected in more than 100 plankton samples collected from 70 inland Wisconsin lakes, including Lake Winnebago. Zebra mussel densities in Green Bay plankton samples were greater than in previous years, reaching a high of 210,000 per cubic meter in a sample collected August 15. Substrate sampler densities peaked in southern Green Bay at 350,000 per square meter on July 26. Scientists collecting samples from Lakes Michigan and Superior indicated that veliger densities at both locations were similar to densities measured last year. This summer for the first time ever veligers showed up in samples collected from the Fox River, several miles above its confluence with Green Bay, Lake Michigan. A moderate density of veligers (1,500 per cubic meter) was collected in a plankton tow south of the De Pere Dam. A small lock connects this area with infested waters downstream. Reports of cooling system intake blockages along the Milwaukee River also indicate that zebra mussels have successfully colonized this river several miles upstream from Lake Michigan. Zebra mussel observers reported relatively low numbers throughout the summer along the Wisconsin portion of the Mississippi River.

ID: 199409-1.

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.