Invasive zebra mussels have been discovered in Minnesota's Cass Lake, distressing officials who worry that the non-native species will spread through the area to infiltrate docks and beaches.
The recent find marks the first time that adult zebra mussels have surfaced in the Bemidji, Minn., area, the SCTimes reported.
Cass Lake will now be designated as an infested lake along with Buck, Andrusia, Wolf, Pug Hole, Kitchi, Little Rice and Big Rice lakes and Pike Bay, eight connected lakes that have also been invaded by zebra mussels.
"We can't date when the zebra mussels first came to Cass Lake but it appears that they have been in the lake for years," said DNR Northwest Region Fisheries Supervisor Henry Drewes, as quoted by the Bemidji Pioneer. "It is very disappointing to find zebra mussels in Cass Lake but it is not a surprise. Fishing boats now come from such a wide area and Cass Lake receives a great deal of pressure."
Female zebra mussels release up to a million eggs in a season, meaning that the species reproduces rapidly to compete for food and other resources with native creatures.
The invasive mussel is native to Europe and was first found in the Great Lakes watershed in 1988. It attaches itself to docks and pipes, sometimes blocking waterways. Because the zebra mussel doesn't burrow into the ground like native mussels, its sharp shell edges can be a problem when boats pull up to a dock or visitors walk on the beaches.
The species appears to be established in Cass Lake, leaving wildlife officials with little to do other than keep an eye on the population and its effects on the local ecosystem.
"We understand the recreational impact [zebra mussels have very sharp shells and will pose a problem to swimmers and waders] but the effect on the ecology is less certain," Drewes said. "We know that in lakes with zebra mussels the water is clearer. The [density] of the zooplankton will change and we will learn how that will affect the fish populations."
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