New Sightings Elsewhere in Upper Midwest

From July 28, 1992 (update #14)

ST. PAUL, Minn. - Three small clusters of zebra mussels were found attached to a barge hauled out at a local drydock in mid-June, according to Minnesota DNR biologist Gary Montz. Since the barge was last in drydock in September 1991, the mussels were probably picked up as adults during the barge's travels, Montz said, because some of the mussels were fairly large (up to 20 mm long). The barge had traveled the length of the navigable Mississippi and Illinois rivers since it was last hauled out, carrying cargo to New Orleans and Chicago as well as the Twin Cities.

ZION, Ill. - "Astounding" densities of zebra mussels were found during July dive surveys on rocky offshore reefs in southern Lake Michigan, according to veteran zebra mussel researcher Ellen Marsden of the Illinois Natural History Survey (INHS). Marsden said a reef off Waukegan, Ill., that had only scattered small numbers of mussels when surveyed last July is now completely covered with the striped mollusks. She reported that another reef offshore from Glencoe, Ill., is 25%-50% covered with zebra mussels. Marsden noted that the coverage of hard substrate "is just like Lake Erie" - a big change from what she observed last year in Lake Michigan. She also noted that water clarity is "out of this world," with visibility of up to 35 feet (nearly 11 m), in contrast to previous summers, when visibility seldom reached 12 feet (about 4 m). On the other hand, relatively low densities of zebra mussel veligers, as compared with last summer's peak densities, have been found to date in samples collected by the INHS, according to biologist Tammy Keniry. Veligers first showed up in samples from Gary, Ind., and Illinois waters of Lake Michigan in mid-June, with earlier sightings occurring farther east near Chesterton and Michigan City, Ind. Settled post-veliger mussels were found only on one date - July 10 - at one location, Keniry said, which is in contrast to frequent observations of settled mussels on sampling devices examined last year in June and July.

ID: 19920728-3.

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.