RELATIONSHIPS BETWEEN FISH COMMUNITIES, HABITAT TYPES, AND ENVIRONMENTAL 
GRADIENTS IN THE UNIMPOUNDED MISSISSIPPI RIVER.

V.A. Barko1, M.W. Palmer2, D.P. Herzog1, and R.A. Hrabik1. 

1Missouri Department of Conservation, Science Division, Open River Field 
Station, Jackson, MO 63755, 2Department of Botany, Oklahoma State University, 
Stillwater, OK 74078.

Spatial variation of fish communities was investigated in response to 
environmental gradients within five habitat types in the unimpounded Mississippi 
River.  These habitats included main channel border, wing dike, open-side 
channel, closed-side channel, and tributary.  Data on fish communities, 
environmental measurements, and habitat measurements were collected between 
Upper Mississippi River (UMR) miles 30 and 80 from 1993-2000 during three annual 
sampling periods.  Partial Canonical Correspondence Analyses revealed variation 
within the habitat types and between the sampling gears, years, periods, and age 
groups (i.e., young-of-the-year and adults).  Habitat use was different for many 
young-of-the-year fish when compared to adults of the same species.  Sampling 
gears employed in this study did not sample the fish community equally and no 
gear type was effective in sampling all subsets of the community.  The fish 
assemblage in this river reach differed the most in 1994.  Many of the adults 
were associated with all three annual sampling periods while young-of-the-year 
fish were often associated with specific sampling periods.  The three main 
environmental gradients influencing community structure for both age groups 
included river stage height, surface water velocity, and conductivity.  Young-
of-the-year goldeye (Hiodon alosoides) and adult blue catfish (Ictalurus 
furcatus) were associated with increased surface water velocity.  Young-of-the-
year common carp (Cyprinus carpio) and freshwater drum (Aplodinotus grunniens) 
were associated with high river stage height.  High river stage height, flooded 
terrestrial habitat, and increased surface water velocity corresponded with the 
first sampling period (June 15-July 30), while increased visibility, decreased 
surface water velocity, and low river stage height corresponded with the third 
sampling period (September 16-October 30).   The results of this study are 
instrumental in better understanding the ecological relationships that exist 
within the unimpounded Mississippi River.

KEYWORDS:  Mississippi River, environmental gradients, habitat, fish community, 
multivariate analysis, ordination.