DISTRIBUTION OF FISHES IN THE NAVIGATION CHANNEL OF THE
MISSISSIPPI RIVER BETWEEN TWO DAMS

John M. Dettmers1, David H. Wahl2, Daniel A. Soluk3, and Steve Gutreuter4
1Illinois Natural History Survey, LTRMP Pool 26 Field Station, 4134 Alby
Street, Alton, IL  62002  2Illinois Natural History Survey, Kaskaskia Biological
Station RR1, Box 157, Sullivan, IL  61951 and Department of Ecology,
Ethology, and Evolution, University of Illinois, Champaign, IL  61820  3Illinois
Natural History Survey, 1910 Griffith Drive, Champaign, IL  61820  4U. S.
Geological Survey, Upper Mississippi Science Center, 2630 Fanta Reed Road,
P.O. Box 818, La Crosse, WI  54610

Large floodplain rivers are spatially complex systems that contain vastly different
aquatic areas.  In the upper Mississippi River, this complexity is altered by the
presence of navigation locks and dams, which tend to create a deeper, more lentic
environment for several miles upstream of each dam.  However, researchers and
managers understand little about fish community composition in the navigation
channel of large rivers, due primarily to sampling limitations, or how the
presence of locks and dams may affect their distribution.  During 1996, we
sampled the navigation channel of Mississippi River Reach 26 with a 10- x 2.4-m rockhopper trawl to estimate relative abundance of juvenile and adult fishes. 
We collected 24 species; gizzard shad and freshwater drum composed about two-thirds of our total catch.  CPUE was greatest in October when current velocity
was low and water temperatures were moderate.  Catfishes, buffaloes, and
freshwater drum were more prevalent in the lower reach immediately upstream
of Lock and Dam 26.  Shorthead redhorse, sturgeons, gizzard shad, and mooneye
were more prevalent in the upper portion of the reach less regulated by Lock and
Dam 26.  Despite its physical severity, the navigation channel of large floodplain
rivers supports substantial fish abundance and diversity.  The distribution of
fishes may be altered by excluding some riverine species while providing more
suitable habitat for others in areas immediately upstream from navigation dams. 
The navigation channel should be considered an important river habitat as we
look to understand large river fish communities.

Keywords: Mississippi River, navigation dam, navigation channel, fish
distribution, fish community

John M. Dettmers, Illinois Natural History Survey, LTRMP Pool 26 Field
Station, 4134 Alby Street, Alton, IL  62002; 618/466-9690; FAX 618/466-9688;
john_dettmers@nbs.gov

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