Spiny waterflea has been confirmed in Basswood Lake in the Boundary Waters Canoe Area Wilderness near the Canadian border.

The discovery was confirmed in zooplankton samples taken by the University of St. Thomas in partnership with the Minnesota Department of Natural Resources fisheries staff. In addition, DNR fisheries staff found spiny waterflea in the stomach contents of Basswood Lake cisco.

The lake will be added to the list of infested waters, along with the following downstream waters: Crooked Lake, Iron Lake and Bottle Lake. The Basswood and Bottle rivers will also be designated as infested waters due to connectivity and the likelihood of infestation spread. Lac La Croix, a water body downstream from Basswood Lake, was designated as infested when spiny waterflea was discovered there in 2008.

“The DNR is coordinating with Canadian officials at the Ontario Ministry of Natural Resources to alert boaters and other recreationists about the risk of spreading the invasive species,” said Rich Rezanka, DNR aquatic biologist.

Spiny waterflea is a small planktonic crustacean that disrupts the food web and competes with small fish as it forages on microscopic animal plankton such as daphnia. Because of its long tail spike, the spiny waterflea is not eaten by small fish.

The species reproduces by a process called parthenogenesis, a form of reproduction in which offspring are produced without fertilization. During most of the year, the species population is entirely female, which allows for rapid population growth. Microscopic spiny waterflea eggs are hardy and capable of overwintering in lakes, and their small size makes them an easy candidate for overland transfer in water or mud.

When populations are high, anglers can experience frustration with masses of spiny waterfleas clogging fishing and downrigging lines, and other water equipment.

Recreationists on these lakes should look for infested waters signage at public accesses. Signage will allow people using the lakes to be aware of the finding and take additional precautions to prevent the inadvertent spread to other lakes. Bait harvest without a permit is prohibited in lakes listed as infested with spiny waterflea.

Anglers, boaters and other recreationists are reminded to remove all aquatic plants, zebra mussels, and other prohibited invasive species, drain water from all water equipment including portable bait containers, and drain bilges and livewells by removing the drain plug before leaving the boat landing.

More information about spiny waterfleas, how to inspect boats and other water-related equipment, and a current list of designated infested waters is available on the DNR website at www.mndnr.gov/ais.