Clough Island: Heart of the St. Louis River Estuary

By Bill Allen 

Shared by Minnesota and Wisconsin, the St. Louis River Estuary is an exceptionally significant natural area due to its diversity of habitats and connection to Lake Superior, the largest of the Great Lakes. And the estuary's centerpiece is Clough Island.

At 358 acres, Clough Island is the largest island within the estuary and one that has long been targeted for both conservation and development.

Thanks to The Nature Conservancy and its partners, Clough Island's future is now clear. It will be conserved for clean water, fish and wildlife habitat and outdoor recreation.

Also known as Whiteside Island and Big Island, Clough Island should be familiar to anyone who has visited the twin ports of Duluth, Minnesota and Superior, Wisconsin. It is located in the middle of the estuary below Lake Superior.

Clough Island's size and prominent location make it a rare and valuable property for wildlife including migratory and breeding birds as well as fish that move between Lake Superior and the river. Clough Island is among the last places in the estuary with long stretches of unaltered shoreline. Shallow wetlands and sheltered bays surround the island, providing critical habitat. The estuary is known for its biological richness and Clough Island is essential to the estuary's protection.

Birds are attracted to Clough Island. It is an important stop-over site for birds that use the St. Louis River Estuary as a landmark on their spring and fall migrations. Waterfowl stop at Clough Island to feed on the American water celery that grows in its wetlands. Songbirds use the island's uplands. As many as 230 bird species have been identified in the area, including 115 known to breed there, making the estuary one of the best bird watching places in the upper Midwest.

Among the birds breeding in the estuary are common terns, a species listed as endangered in Wisconsin and threatened in Minnesota. In recent years, about 200 pairs of common terns have nested in the estuary, which is nearly two-thirds of the entire Lake Superior basin population. The sandy, open-water flats near Clough Island are an important fishing area for common terns feeding on emerald and spottail shiners, minnows that are their primary food source.

The minnows that attract the terns are among the 45 native fish species documented in the estuary. Many are important to the region's sport fisheries, such as walleye, muskellunge and smallmouth bass. The estuary is especially important for fish that ascend the river from Lake Superior to spawn. The shallows surrounding Clough Island provide an essential nursery area for juvenile fish to develop before moving into Lake Superior.

In fact, the largest of Lake Superior's fishes can be found in the St. Louis River Estuary not far from Clough Island. Lake sturgeon, which can exceed eight feet in length and weigh more than 100 pounds, are starting to return to the St. Louis River. With improved spawning habitat below the Fond du Lac dam, scientists hope that lake sturgeon will once again reproduce within the estuary, which historically was the prime spawning ground for the species' population in western Lake Superior. Clough Island's wetlands will serve as a nursery area for juvenile lake sturgeon until they are large enough to move into Lake Superior.

Preserving Clough Island and other key natural areas in the Lake Superior Basin helps keep our water clean. In Minnesota, Duluth, Beaver Bay, Grand Portage, Silver Bay and Two Harbors all draw their drinking water directly from Lake Superior. Cloquet, Minnesota. also relies upon Lake Superior as its backup water supply. And the city of Superior in Wisconsin gets its drinking water directly from Lake Superior.

By acquiring Clough Island, The Nature Conservancy preserved a natural asset that is critical to Minnesota, Wisconsin and the Great Lakes.

In 2011, The Nature Conservancy transferred Clough Island to the State of Wisconsin for long-term protection and management as part of the St. Louis/Red River Stream Bank Protection Area.

Bill Allen is a volunteer writer for The Nature Conservancy.


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