Illinois Sitings: Fox River

From May, 1997 (Update #30)

Jim Stoeckel, Illinois Natural History Survey (INHS) biologist, reported one potential new Illinois river infestation from the Fox River. INHS scientists sampled the Illinois River system downstream from Lake Michigan in early September and also sampled tributaries to determine whether veligers were entering the Illinois River system from any upstream tributaries. They found small numbers of veligers in the Fox River (0.6 per liter), less than one mile upstream from its confluence with the Illinois River, near Ottawa. Veliger abundances in the Illinois River upriver of the Fox River varied between approximately 10 and 170 larvae per liter. During this survey veligers were also found in the Chicago River, Chicago Ship and Sanitary Canal, Cal-Sag Channel and Des Plaines River downriver of its confluence with the Chicago Ship and Sanitary Canal. No zebra mussel larvae were found in the Kankakee River. Although Stoeckel reported he could not prove conclusively the Fox River veligers didn't come from the Illinois itself, he observed that the water at the sample location was green, which was quite different from the typically brown Illinois River water. In addition, the downstream current at that location was fairly swift, suggesting the Illinois River water would not likely back up to that location. This is the second report of veligers from within the Fox River system in northeastern Illinois. Seventeen veligers (a density of 24 per cubic meter) were found by Wisconsin Sea Grant biologists examining a July plankton sample collected from Bluff Lake, one of the Fox Chain of Lakes near McHenry. Eight plankton samples collected on one prior and three subsequent dates in 1996 contained no veligers. No veligers were found throughout the summer in 67 additional plankton samples collected from other upriver and downriver basins in the Fox Chain.

ID: 199705-13.

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.