Spiny waterfleas found in Namakan

Voyageurs National Park staff confirmed the presence of spiny waterflea (Bythotrephes longimanus) in Namakan Lake on Oct. 10.
Spiny waterflea, a non-native zooplankton, was found on Rainy Lake this summer, but detection monitoring at that time on the Namakan reservoir did not reveal its presence.
Staff from the University of Minnesota’s Sea Grant program later observed the waterflea in Namakan Lake in early October and alerted park managers.
Park staff sampled the site using a plankton net, and observed and confirmed the presence of the aquatic exotic species.
Experts believe spiny waterflea originally arrived in the U.S. from Eurasia in the ballast water of cargo ships when they were found in Lake Ontario in 1982 and Lake Superior in 1987.
Boaters and anglers most likely have spread them to inland waters since then.
Waterfleas collect in masses on fishing lines and downrigger cables. The masses can resemble gelatin or cotton batting with tiny black spots, which are the creatures’ eyes.
Individual ones are difficult to distinguish without magnification because they are only 1/4-5/8 inches long.
Since spiny waterfleas are new to these lakes, their impact can be potentially devastating to aquatic organisms.
Spiny waterflea will compete with native zooplankton and minnows for food. This competition can disrupt the food chain at its base with potentially significant effects farther up the chain.
This winter, park staff and partners will develop a strategy:
•to prevent the spread of spiny waterflea to uninfested waters;
•to research the effects of the introduction; and
•to educate the public in ways they can help in the fight against this aquatic nuisance species.