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CHAPTER IV: WILFLIFE HABITATS FOR MISSISSIPPI’S SGCN,

THREATS AND CONSERVATION ACTIONS^180

From 1999-2003, 47 percent of the fish kills investigated by MDEQ were associated with low dissolved
oxygen, 10 percent with nutrient overloads and 5 percent with pesticides. Fish kills in certain oxbows
are expected each year due to low dissolved oxygen.

Exotic species, some of which are quite aggressive, now present a threat to native lentic communities.
Particular types of concern include aquatic plants (hydrilla), fish (Asian carp) and zebra mussels. Exotic
zooplankton species are also reportedly present in Mississippi lakes. The exotics could impact the low-
end of the food chain for many fishes including sport fish and filter feeders such as paddlefish.

Since very few new oxbow lakes can be expected to be created naturally, long-term management
approaches for the lakes that already exist are needed. Artificial restraints and other impacts on many
streams alter the natural association of streams with their oxbows. Management approaches that
integrate various stakeholders will be important in the future to effectively preserve oxbow habitats.
Recent efforts toward reforestation and best management practices in forestry and agriculture have
helped to reclaim landscapes around streams and oxbows.

11.1 Oxbow Lakes

„ Value to SGCN - 86

„ Rank - 6th of 18 Lotic and Lentic Systems

DESCRIPTION
Oxbow lakes provide important habitat for aquatic
species and a wide range of recreational
opportunities. Oxbow lakes are created naturally over
extended time periods as streams abandon their old
channels. Manmade alterations such as
channelization may also convert old stream channels into oxbow lakes. Natural formation involves
gradual loss of connectivity with the stream as sediment fills the ends of old channels. During periods of
low stream flow, smaller pools in oxbow lakes may develop lethal conditions for species that are
intolerant of high water temperature and low oxygen levels. Manmade weirs placed near the outflows of
oxbow lakes can retain lake levels after stream levels decrease. For example, the weir project in 2002
on Tunica Cutoff, an oxbow along the Mississippi River, greatly improved fishery resources by
increasing water depths during the summer and fall growing season.

Oxbow lakes support a variety of fish, amphibians, reptiles, mammals, and wading and shorebirds.
Although floods often cover oxbow lakes and allow fish to move freely in and out, the exchange of
nutrients from rivers and their watersheds to the oxbow lakes is the most important factor determining
higher fish abundance. Frequency, duration and timing of floods are important considerations in the