The invasion by non-native species is an ever increasing concern in the Great Lakes basin. Non-native species are those that do not naturally exist in an environment and have been introduced by human activity, either intentionally or unintentionally. Introduction of species has occurred through a variety of sources including intentional stockings, ballast water carried in international commercial vessels, the building of canal systems, gardening and angling. They have both ecological as well as economic impacts, effecting commercial fishing, agriculture, tourism, sport fishing, recreation, utilities and more.

Non-native species in Lake Superior continue to influence the functioning of the ecosystem because parasites and predators that act as natural controls in their native habitat are not present here. In 2000, the Minnesota Sea Grant reported observations of 28 non-native species in Lake Superior, 17 fish, five aquatic invertebrates and six aquatic plants.

Ship ballast continues to be a primary source of unintentionally introduced non-native species in Lake Superior. Some of the non-natives such as sea lamprey are found throughout the lake, while others such as round nose goby, ruffe and three spine stickleback are found in limited areas of the lake. Non-native aquatic plant species of concern include purple loosestrife and Eurasian water milfoil.

Gypsy moths were introduced in the late 1800's and are one of North Americas most devastating forest pests. Widespread defoliation of forest stands occurs in peak years. The Asian longhorned beetle is native to China and is a hardwood tree pest. It is believed to have been imported in untreated wood used for pallets and packing materials. These beetles spread rapidly from tree to tree, killing trees by boring holes deep into them. The hemlock woolly aphid is another non-native insect. It primarily attacks hemlock trees, with spruce possibly being a secondary host. Immature nymphs and adults damage trees by sucking sap from the twigs which causes them to drop their needles to the point of defoliation.

Leafy spurge is an invasive plant with roots that can extend 35 feet, grows through asphalt, and flings it's seed 15 feet. The deep root system enables it to survive disturbances and resprout even after the foliage is destroyed. Non-native honeysuckles have been used as ornamentals in gardens for decades, and birds carry their seeds to natural habitats. Once established, honeysuckle can dominate the understory of woodlands. Other non-native plants causing problems include exotic buckthorns, garlic mustard, and spotted knapweed.

Binational initiatives are currently dealing with non-native species in Lake Superior as well as throughout the Great Lakes basin. Agencies and Native American Tribes from the United States and Canada continue fish surveillance surveys to document the range expansion of ruffe and detect other non-native species from Thunder Bay, Ontario to Sault Ste. Marie, Mich. In 2003, round goby and white perch were discovered and confirmed in Thunder Bay Harbour, Ontario. Fish community surveys continue in the St. Louis River and four other south shore rivers to monitor fish community structure in tributaries colonized by ruffe and other non-natives. Thousands of acres are being treated annually to control the spread of non-native plant species by governmental and non-governmental organizations alike. Educational materials such as pocket guides, signage at boat landings, brochures and videos continue to be produced by Sea Grant, the Binational Program partners and others. These materials are distributed throughout the Lake Superior basin to prevent the introduction and reduce the spread of non-native species.

What can you do to help stop the invasion? A few simple actions will help prevent the spread of non-native species to your favorite portion of the Lake Superior basin. Inspect your boat and trailer and remove any plants and animals before leaving the water body. Drain water from the motor, livewell, bilge and transom before leaving the water body. Never release live bait fish in the water or live earthworms on the land or water. When planning landscaping or gardening activities use only plants native to the region. Consult with professional garden centers and landscape planners on the best native plants for your area. Learn what non-native species look like and additional prevention tips by contacting your local state or federal natural resource management agency and ask for information and identification material for non-native species.