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Upper Midwest Environmental Sciences Center

Bioassessment of the Finger Lakes Habitat Rehabilitation and Enhancement Project: Responses of Fish and Aquatic Invertebrates

The Upper Mississippi River System has been highly modified for human uses since the late 1800s. One effect of these modifications is that many side channels and backwaters are slowly filling with sediment.

Sedimentation reduces water flow into these areas and decreases habitat quality for fish. To counteract these effects, managers often attempt to increase flow into backwater areas by dredging channels or building structures that direct flow out of the main channel to backwaters.

The Finger Lakes area of the Upper Mississippi River is a system of six connected backwater lakes just below Dam 4 near Kellogg, Minnesota. Most of these lakes receive little flow from the main channel except during floods. Many lakes experience periods of low dissolved oxygen levels especially during winter. Winter is a particularly stressful time for river fish and poor winter habitat may be limiting for some populations.

Pool 5 - Reach 1 - Upper Mississippi River

Photo caption: Doe Run Smelter, Herculaneum, Missouri, showing Joachim Creek In 1993, the U.S. Army Corps of Engineers installed culverts to introduce flow into each of the Finger Lakes. Each culvert was fitted with a valve to control flow.

A multiagency study was begun in 1991 to determine the effects of introduced flow on sediments, water quality, vegetation, invertebrates, and fish (especially bluegill, black crappie, and largemouth bass).

The purpose of this study is to determine the flow rates that produce optimal habitat for fish, primarily in winter, with the goal of increasing fish populations.


These results can be applied to many similar projects conducted on the Mississippi River and other rivers throughout the United States. The project was completed in September 2000.

Principal Investigator: Barry Johnson

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