New Sightings in Wisconsin

From November 11, 1992 (update #15)

CASSVILLE - Wisconsin power plants along the Mississippi River reported for the first time finding zebra mussels on substrate samplers adjacent to their water intakes. Two zebra mussels were found in August on a substrate sampler at the Wisconsin Power & Light (WPL) Nelson Dewey Generating Station near Cassville. The generating station pulls raw water from Pool 11 of the Mississippi River. WPL Master Lab & Instrument Technician Dennis Blackbourn placed the substrate sampler (a cement brick) in an intake well on June 11. A small (2 mm) mussel was found on Aug. 13, and a medium-size (7 mm) mussel was found on Aug. 26. Three zebra mussels were found in October at Dairyland Power Company generating plants on the Mississippi River. On Oct. 12, Dairyland Environmental Biologist John Thiel found a single zebra mussel attached to a substrate sampler at the company's E.J. Stoneman generating facility near Cassville. The next day, Thiel found another solitary mid-size (11 mm) adult mussel at the Alma Generating Station, and another mussel the same size at the Genoa Generating Station on Oct. 28. All of these mussels were found on substrate samplers placed adjacent to the power plant pump houses. Thiel said that all samplers had been checked at least once every other week since early summer, and that these were the first mussels found on the samplers. In the Great Lakes, finding mussels on substrate samplers has often been the first sign of serious levels of infestation.

ST. PAUL, Minn. - Divers conducting routine maintenance and inspection surveys of Mississippi River navigation locks continued to find zebra mussels throughout the summer, according to U.S. Army Corps of Engineers (COE) biologist Tim Yager. Starting in late July, mussels were found at Lock & Dam structures #2, #3 and #4 between Hastings, Minn., and Alma, Wis., and at Lower St. Anthony Falls. Most of the mussels were found on the lock chamber floors by COE divers, Yager said. Clam surveys in Mississippi River turned up zebra mussels in the pool behind Dam #7 (Lake Onalaksa) and Pool 8 upstream of Genoa. The mussels were attached to the shells of 12 three-ridge clams which, according to Yager, are among the most abundant native clams. Each parasitized clam supported a single zebra mussel. About 600 native clams were collected in all. Several more zebra mussels were found attached to native clams in Pools 4 (upstream of Alma) and 6 (upstream of Trempealeau) by U.S. Fish & Wildlife Service personnel.

LA CROSSE - Wisconsin Department of Natural Resources fishery biologist Ron Benjamin reported receiving 20 to 50 calls a week during September and October from people finding zebra mussels on piers, boats, irrigation pipes and other structures in the Mississippi River. The reports began to flood in as people began removing these structures from the river in late summer and early fall, Benjamin said. These included the first reports in Wisconsin of zebra mussels infesting irrigation systems. The mussels were found at the river end of pipes carrying water to irrigate domestic lawns. Some of these systems cost as much as $25,000, he said. Benjamin said he also received numerous reports of zebra mussels on large houseboats.

GREEN BAY - The first confirmed sighting of a zebra mussel in the lower Fox River occurred Nov. 2 about a mile upstream of the river's mouth at Green Bay. Green Bay Metropolitan Sewerage District biologist Dick Sachs found a single large (18 mm) mussel attached to a water quality sampling station in the Fox River.

EGG HARBOR - The first report of zebra mussels in Door County north of the Sturgeon Bay Ship Canal occurred Oct. 4, when cottage owner Jay Mortell found three of the mussels on a ladder attached to his Egg Harbor swimming dock. Mortell said the dock (with the ladder attached) was placed in the water earlier in the summer.

MILWAUKEE - The M/V Iroquois, a Milwaukee Harbor tour boat, was found to be "heavily encrusted with zebra mussels" when lifted out of the water Oct. 20 for routine maintenance, according to University of Wisconsin Sea Grant Advisory Services field agent James Lubner. The boat had not been removed from the water for four to five years. According to Lubner, the lower part of the hull, from about a foot and a half below the waterline and down, was covered with mussels. "It was really thick for most of the length of the boat - an inch to two inches thick," he said. "I didn't see thatmany little ones, just big ones attached to even bigger ones." The M/V Harbor Seagull, a Port of Milwaukee work boat lifted the same day, had only small numbers of zebra musssels attached to its hull. It had been last removed from the water early in 1991. Neither boat's hull had been painted with antifouling paint. In late October, Lubner observed zebra mussels attached to mooring buoys and three shopping carts retrieved from the harbor near Milwaukee's South Shore Yacht Club, and he saw mussels on nearby county launch ramps that had been recently removed for the winter. However, yacht club members reported that virtually no zebra mussels were found attached to boats moored in the harbor, probably due to the use of antifouling paint on the hulls.

MILWAUKEE - Zebra mussels continued to cause problems at Lake Michigan power plants in August and October. WEPCO Senior Results Technician John Babinec reported in late August that "every time we pop some piece of equipment open at our Oak Creek Power Plant we find zebra mussels." In late October, Babinec reported that zebra mussels continued to show up deep inside the Oak Creek facility, which means the miles of small diameter pipelines that provide cooling and service water are infested.

RACINE - Veliger monitoring at the Racine Water Utility intake turned up larval zebra mussels at very high densities (30,000 per cubic meter) in early August, according to data provided by plant superintendent Herb Schmidt. Schmidt reported that this summer's water temperatures were lower than average, water turbidity was down, and an increased abundance of the bluegreen alga Spirogyra was also evident. A similar report of cooler-than-normal temperatures, reduced turbidity and abundant Spirogyra was also confirmed by Ellen Flanagan of the Chicago Water Utility. Both Flanagan and Schmidt reported that Spirogyra was infrequently found in previous years.

MILWAUKEE - Zebra mussel veligers were found Aug. 7 at low densities (1 per liter) at an offshore Lake Michigan sampling station east of Milwaukee, according to UW-Milwaukee biologist Craig Sandgren. The water depth at the station was 65 feet (20 meters). On the same day, water samples taken at a station farther out in the lake - at a depth of 330 feet (100 meters) - contained veligers at very low densities (1 per 100 liters).

MILWAUKEE - Reports of extraordinary water clarity in southern Lake Michigan continued into the fall. Wisconsin Electric Power Company (WEPCO) Senior Environmental Scientist Dave Michaud reported that a WEPCO crew returning by boat from the Oak Creek Power Plant in late October could see the bottom in 27 feet (8 meters) of water near Black Can Reef south of Milwaukee. These and other southern Lake Michigan water users - including commercial fishers, water utility officials and scientists - have repeatedly commented that they've never seen conditions like this previously.

ID: 19921111-2.

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.