St. Louis River Alliance

Habitat Issues and Concerns in the St. Louis River

Situated at the far western end of Lake Superior, the St. Louis River is the largest of the U.S. rivers that drain the Lake Superior basin. Its average annual flow is 2323 cubic feet per second as measured at Scanlon, Minnesota. As the river nears lake Superior, it enters a broad, flat freshwater estuary, or drowned river mouth. The lakeward boundary is the sandy, bay-mouth bar system composed of Minnesota and Wisconsin Points. Seiches (oscillations in Lake Superior water levels caused by winds or atmospheric pressure) can reverse the direction of the river’s flow as far upstream as the Fond du Lac dam, some 21 miles from the river’s natural outlet to Lake Superior.

When first charted by William Hearding in 1861, the estuary was primarily a shallow area with a variety of wetlands and riparian forest communities. Upland forests tended to be dominated by coniferous and mixed deciduous/coniferous stands that lengthened the spring snow-melt period and slowed runoff. A thick layer of organic duff on the forest floor also tended to slow the movement of water from the land into the estuary. A variety of fish, waterfowl, fur bearers and other wildlife used the estuary for breeding and migration. Despite significant changes in the area, the estuary still provides vital habitat for fish reproduction, nesting colonial water birds and waterfowl, migratory shorebirds and songbirds, and many other animals. The estuary supports a large, diverse warm-water fish community of approximately 54 species, including lake sturgeon, walleye, yellow perch, northern pike, burbot (eelpout), black crappie, emerald shiner, spottail shiner and white sucker.

Many of the changes in the landscape have resulted in speeding up the movement of water from the land into the estuary. Pavement and storm drains move water quickly into streams and ditches. Today’s early successional forests and deciduous forests do less to slow snowmelt than did the original coniferous forests. Faster runoff results in greater peak flows in streams and greater erosion of stream banks. Many of the changes in the estuary have resulted in loss of shallow, marshy aquatic habitat. Filling of wetlands and open water to provide areas for river-side development has caused a loss of about 3,000 acres. Another 4,000 acres of the estuary have been dredged or deepened for navigation.

Issues of concern relating to the habitat of the area include the historic loss of wetlands and shallow water habitats. With almost 60% of the estuary either dredged or filled, habitats have been severely altered.

Hydropower development in the St. Louis River watershed has dramatically changed the hydrology of the river system. Several large reservoir lakes and five hydro-power dams now influence the quantity and quality of water in the lower reaches of the watershed.

A variety of historical discharges resulted in severely degraded water quality in the harbor until relatively recently. These discharges caused fish kills, fish tainting and likely reduced the reproductive success of colonial water birds.

Exotic species continue to be a problem in the estuary. Species such as the sea lamprey have had major impacts on the ecosystem of the St. Louis River and Lake Superior. More recent introductions of species such as the ruffe, purple loosestrife, zebra mussels and others may have impacts of equal magnitude.

Contaminated sediments, mostly left from the area’s industrial past, have degraded benthic invertebrate habitat, altering the structure of invertebrate communities. These contaminated sediments are a continuing source of toxic chemicals to the estuary’s food web. Fish and birds, feeding on aquatic insects that have become contaminated, may experience reproductive problems, deformities and tumors.

Impaired Beneficial Uses:

Degraded Fish Populations, due to impact of exotic fish species, altered hydrology, contaminated sediments, accelerated erosion and historic water quality problems.

Degraded Wildlife Populations, due to a loss of Piping Plover nesting habitat, and a decline in Common Tern nesting habitat.

Degradation of Benthos, due to contaminated sediments.

Loss of Fish and wildlife Habitat, due to wetland filling, contaminated sediments, harbor development (residential, commercial and industrial).

Many efforts are underway to improve habitat conditions in the St. Louis River estuary. The establishment of the Western Lake Superior Sanitary District (WLSSD) wastewater treatment plant in 1978 improved habitat conditions in the area by dramatically improving water quality and decreasing the input of new chemical contaminants. Fish and wildlife populations and communities have been rebounding since that time.

The importance of planning for land use and for habitat protection and restoration has been recognized through a RAP recommendation about a habitat plan, the City of Duluth’s comprehensive land use planning process and natural resources inventory, a Wisconsin coastal wetlands inventory, the Nemadji River Basin Project, and the Park Point Protection Project. Additional work to maintain ecosystem functions and features has been accomplished through the acquisition and management of much of the Red River watershed by the Wisconsin DNR. The Minnesota DNR recently purchased over 22,000 acres of important riparian habitat on the shores of the St. Louis, Cloquet and Whiteface rivers in the St. Louis River watershed.

Habitat restoration is also underway in the AOC. Citizen groups are working to restore water quality and streamside vegetation on Miller Creek and other urban tributaries to the estuary. A project to restore wetland functions at Grassy Point, where an old road and thousands of cubic yards of sawmill waste were removed. Planning is underway at that site to establish wetland trails and wildlife viewing platforms. Common Tern management at Interstate Island, a joint Wisconsin and Minnesota Wildlife Management Area, has seen recent success at improving tern reproduction by managing nesting habitat. These and other projects all seek to restore and maintain the ecological functions that make the St. Louis River estuary such a diverse and productive ecosystem.

The CAC’s Habitat Committee

The CAC’s Habitat Committee has developed a number of recommendations related to habitat issues in the St. Louis River AOC. The committee is currently assessing progress made to date on existing recommendations, and is fleshing out details needed to implement the recommendation that calls for the development of a comprehensive habitat plan for the harbor.


Moyle, J.B., and W. A. Kenyon. 1947. A biological Survey and fishery management plan for the streams of the St. Louis River System. Minnesota Dept. Cons. Inv. Report 69.

Peterson, A.R. 1979. Fish and Wildlife Survey of the St. Louis River. Minnesota DNR. Special Publication No. 127.