Aquatic invasive species (AIS) are the species that invade our lakes, rivers, and wetlands. Many non-native species are not problematic; however, a select few are extremely competitive and pose a significant threat to our native ecosystems.
AIS that are problematic in the St. Croix watershed include: zebra mussels, Eurasian watermilfoil, banded mystery snails, purple loosestrife, and curly-leaf pondweed, among many others. Invasive bighead and silver carp are present in the lower St. Croix River south of Stillwater, but as of right now, there are no current reproducing populations in the St. Croix River. Black carp and grass carp are a potential future invader.
Learn more about how we are dealing with invasive species: