New Sightings in Wisconsin

From September 16, 1993 (Update #18)

LADYSMITH -- Recently settled zebra mussels were discovered on three substrate samplers retrieved August 25 from the Flambeau Hydro Station north of here, according to John Thiel, environmental biologist for the Dairyland Power Cooperative in LaCrosse. This is the first reported observation of zebra mussels in an inland Wisconsin lake or river, other than the Mississippi River. The company discovered 42 post-veligers in a routine sampling operation at their power station on the 2,000-acre Dairyland Reservoir, an impoundment of the Chippewa River. U.S. Fish and Wildlife Service scientists at the Fisheries Research Center in LaCrosse confirmed Thiel's identification of the samples as zebra mussel larvae. Thiel said the origin of the mussel larvae is unclear and that he was surprised by the high density. The post-veliger densities found on substrate samplers near Ladysmith were higher than those found this summer at Dairyland power plants along the Mississippi River, he said. Additional surveys of the Dairyland Reservoir will be conducted by Dairyland Power to determine the extent of zebra mussel colonization in the neighboring area and the source of the larval mussels.

MILWAUKEE -- High veliger densities were found in late August at two Wisconsin Electric Power Company (WEPCO) power plants, according to Senior Results Technician John Babinec. Very high densities (50,000 per cubic meter) were measured at the Pleasant Prairie Generating Station near Kenosha. Slightly lower figures (22,000 per cubic meter) were recorded at Point Beach Generating Station north of Two Rivers. (These were the highest levels of veligers ever recorded at Two Rivers' Point Beach.) During most of July and early August veliger densities had been low at both these plants. By the first of September, however, Pleasant Prairie veliger densities had dramatically decreased (6,300 per cubic meter). Knowing when peak zebra mussel reproduction occurs, Babinec said, is helpful in knowing when to chlorinate WEPCO water systems.

WASHINGTON ISLAND -- A diver retrieved a zebra mussel from 15 feet of water near Pilot Island, according to Susan Rock, a seasonal naturalist at Rock Island State Park. Veligers were found in a water sample taken from the main harbor on Washington Island earlier this summer.

ID: 19930916-2.

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.