Editor's Note

From July 15, 1993 (update #17)

Zebra mussels actively reproduced in the Wisconsin waters of Lake Michigan during May and June - the earliest reproduction observed in these waters to date. No signs of zebra mussel reproduction have been seen in Lake Superior this year. On July 13, recently settled, pinhead-sized (1 mm) mussels were found at very high densities (260,000 per square meter) on samplers in southern Green Bay near Dyckesville. This is 10 times greater than the highest density found on any Wisconsin Zebra Mussel Watch substrate sampler so far. Sampling began in late May. By July 6, zebra mussel larvae (veligers) were detected in 16 of 21 samples from Green Bay, Lake Michigan, at densities as high as 5,000 per cubic meter - the largest veliger concentrations ever found in the bay. Although no veligers were found in a sample collected near Whaleback Shoal in northern Green Bay, veligers were discovered as far north as Washington Island harbor on June 11. Veligers were also found in the first water sample - and all 11 subsequent samples - taken this season from Milwaukee and Racine harbors. By mid-June, relatively high densities (up to 30,000 per cubic meter) were found at Milwaukee. Eight of 11 water samples taken from harbors at Port Washington, Manitowoc and Sheboygan also revealed veligers. And, the season's first recently settled mussels were found on substrate samplers at Kenosha on June 11 and in Milwaukee harbor on June 13. The samplers had been in place for two weeks. No veligers were found in samples taken from Marinette and Superior harbors, nor in any samples from Lake Winnebago. Due to extraordinarily high water conditions, reports from inland river monitoring for zebra mussels were unavailable. It's worth noting that, as of July 15, no sightings of zebra mussels have ever been confirmed for an inland Wisconsin lake.

ID: 19930715-1.

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.