Counting Mussels on the Wall

From May, 1995 (Update #24)

LA CROSSE, Wis. - A January dive inspection of a Dairyland power plant water intake was used to compare two different techniques of counting settled mussel densities. According to Dairyland biologist John Thiel, counts taken underwater were 30-35 percent lower than densities estimated in the lab from wall scrapings. Divers conducted underwater counts of attached mussels in an intake forebay, comparing them to counts made above water from material scraped into a plankton net. The scraped material was taken from one-quarter-meter-square wall sections. Underwater counts consistently missed smaller mussels that had settled in late summer and early fall, despite the fact that January water conditions were relatively clear. Since the "scrape" method did not take more time, Thiel said Dairyland would probably continue to use this counting method in the future.

ID: 199505-9.

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.