Two Mississippi Lakes Revitalized As Fisheries

Fishermen can now cast their lines into two Mississippi freshwater lakes that have been revitalized as sports fisheries.

Natural lakes in the Mississippi Delta, long known for their productivity and recreational value, have declined because of poor water quality. Sediment from agricultural runoff interferes with plankton growth, the foundation of all life in freshwater lakes.

Now, best management practices (BMPs) have been designed to reduce sediment-laden runoff from agricultural lands and improve water clarity. ARS ecologist Scott Knight at the National Sedimentation Laboratory, Oxford, Miss., conducted a study to evaluate the restocking of sports fish in three lakes with watersheds that have been improved by implementing BMPs.

The lakes under study are called oxbow lakes, created when a river cuts a new path across a large bend--usually during flooding--and isolates a u-shaped section of the river. Oxbows make perfect ecology laboratories because they are essentially closed ecosystems.

Sports fish were successfully reintroduced in the two lakes whose watersheds were protected with culture-based BMPs like conservation tillage and cover crops. Structural BMPs used to reduce water flow speeds and filter sediment included grade stabilization structures, like slotted inlet pipes; tall fescue grass filter strips, and riparian forest buffer zones. The third lake was protected by only structural measures which did not reduce sediment enough to ecologically improve it.

The two lakes protected by culture-based BMPs had the most significant improvement in water quality. Increasing water clarity boosts plankton growth, a necessity for a good sports fishery. Bass populations, lacking before renovation and restocking, were successfully established in these two lakes.

The scientists say their results indicate that cultural BMPs may play a more significant role in improving lake water quality and may be needed in addition to structural measures to ensure improvement of fisheries in oxbow lakes. ARS is the U.S. Department of Agriculture’s chief scientific research agency.

Scientific contact: Scott Knight, ARS National Sedimentation Laboratory, Oxford, Miss., phone (662) 232-2935, fax (661) 232-2934, knight@sedlab.olemiss.edu.