St. Croix Stays Clean. . .

From May, 1997 (Update #30)

A boater interception program and educational efforts designed to slow the spread of zebra mussels into the St. Croix River continue to show favorable results, according to Sue Jennings of the National Park Service St. Croix National Scenic Riverway. The riverway is home to a number of unique native mollusks that could be threatened by zebra mussels. Although small numbers of zebra mussels have been found within the southern reaches of the riverway, no evidence of reproducing or self-sustaining zebra mussel populations has been found. Most zebra mussels have been found attached to boats, which reportedly spent time in the infested waters of Lake Pepin, an area of the Mississippi River located 25 miles south of its confluence with the St. Croix. In 1996, active monitoring for zebra mussels within a restricted area of the St. Croix was conducted by several agencies (see ZMU #28). Underwater inspections of preselected sites took place May through October from Stillwater to Prescott, Minn. The 25 inspection sites included bridges, piers, buoys, native mussel beds and marinas, and boats were also examined as they were removed for winter storage. Of the 25 boats found to have attached zebra mussels, 22 were discovered when removed from the water in fall, and the other three were detected during routine monitoring dives, at which time the boats were removed from the water and cleaned. August plankton samples from the river contained no veligers. Three solitary zebra mussels were also found attached to native mussels in late August (see ZMU #29) during a native mussel relocation project. No additional mussels were found at this location in an October monitoring dive. Because this site is a popular beach area, Jennings speculated that the zebra mussels had been dislodged from boats beaching on the Wisconsin shoreline, then reattached to native mussels in the area - again, suggesting no zebra mussel reproduction is occurring within the St. Croix.

. . . But Is It Clean Enough? The Minnesota-Wisconsin Boundary Area Commission (MWBAC) has called for lawmakers in both states to take stronger action to keep zebra mussels out of the St. Croix River. During a February meeting the commissioners toned down an earlier proposal that asked the states to immediately impose temporary restrictions on boats moving from the Mississippi River into the St. Croix. Options such as blocking all boat traffic and inspecting all boats were discussed by commissioners at the MWBAC meeting, and addressed by state and federal officials. During the boating season, about 300 vessels pass daily from the Mississippi near Prescott, Wis., into the Lower St. Croix, according to the Minnesota DNR. On weekends and busy holidays this number can double or even triple. One MWBAC commissioner, Buck Malick, was quoted by the St. Paul Pioneer Press in support of the measure by stating, "If we lose the St. Croix and allow this mussel to get a foothold, we will have useless beaches, and all the fine things that this river means to this valley 200 miles on either side will go down the drain." The MWBAC is an advisory commission without legislative authority, therefore relies on state legislatures for implementing their recommendations. Gary Montz, Minnesota DNR biologist, reported in late April that no bills implementing stronger preventive measures had been introduced this session by Minnesota legislators.

ID: 199705-1.

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.