Aquatic invasive species (AIS) are non-indigenous species that dwell in water or wetlands whose introduction causes or is likely to cause economic or environmental harm or harm to human health.  When AIS arrive in Polk County they have a competitive advantage over native species because they lack natural predators, parasites, pathogens, diseases, and competitors to keep their populations in check.  As a result, populations of AIS can explode and outcompete native species by using available resources.

Additionally, many AIS have life strategies which give them a competitive advantage over native species.  Strategies include high reproductive rates, early seasonal growth and development, and tolerance for a wide range of environmental conditions.

Invasive species can come from other parts of the United States or from other countries and can be released either intentionally or unintentionally.  Modes and reasons for introduction can vary widely and include: ballast water for shipping, food sources, bait sources, and the garden/aquarium plant trade.  Although some species may have been introduced through natural migration, humans are the primary way invasive species are spread.

AIS can displace native species; reduce wildlife habitat; and negatively impact property values, recreational activities, tourism, and industries.

Aquatic Invasive Species Background Information
Wisconsin Transport Laws for Boaters and Anglers
Mystery Snails
Curlyleaf Pondweed
Eurasian Water Milfoil
Japanese Knotweed
Purple Loosestrife
Rusty Crayfish
Zebra Mussels