Wildlife managers from the Minnesota Department of Natural Resources (DNR) are again finding dead lesser scaup on Lake Winnibigoshish (Winnie) this fall.
Although not yet confirmed, the ducks are suspected to have died from acute infestation of intestinal parasites called trematodes, which are carried by Faucet snails, an invasive species that inhabits lakes. Lesser scaup feed on the snails and become infected with the trematodes.
During the first 10 days of November about 100 to 200 dead scaup had been observed along the northwestern shoreline of Winnie in the Third River Flowage area, according to Grand Rapids Area Wildlife Manager Perry Loegering, who along with office staff conducts weekly searches of the west shore of Winnie, Bowstring and Round lakes. A small number of sick and dead scaup have been observed on Bowstring and Round lakes as well.
"Faucet snails have not been found in Bowstring or Round lakes, so we think the birds are moving from lake to lake feeding on Winnie but getting sick on the other lakes," Loegering said.
DNR officials are studying Faucet snails in infested waters to learn more about their habitat use, abundance and parasite prevalence. These waters include Winnie, Upper and Lower Twin lakes, Shell River, First and Second Crow Wing lakes, and Crow Wing River.
Officials continue to sample Round and Bowstring lakes to facilitate early detection of Faucet snails. They are also sampling areas where scaup are feeding to learn where scaup are most likely to encounter snails.
Die-offs of lesser scaup have occurred on Winnie in 2007 and 2008 when an estimated 8,000 and 2,000 scaup died, respectively. About 2,000 scaup were estimated to have died on Bowstring in 2010.
The DNR reminds hunters, anglers and other recreation boaters to check their boats, trailers, anchors, decoys and lines, and other submersed equipment when moving between waters.
The best way to reduce the spread of Faucet snails is to prevent their transport.