SPATIAL VARIATION OF FISH COMMUNITIES IN THE UPPER MISSISSIPPI RIVER BASIN

John H. Chick 1, Mark A. Pegg 2, Todd M. Koel 3, 1 Illinois Natural History 
Survey, Great Rivers Field Station; 2 Illinois Natural History Survey, Illinois 
River Biological Station; 3 National Park Service, Yellowstone National Park.

Since 1991, researchers with the Long Term Resource Monitoring Program have 
collected fish abundance and composition data from six regional trend areas 
(RTA) in the Upper Mississippi River System (UMRS): Mississippi River navigation 
pools 4, 8, 13, and 26, the La Grange pool of the Illinois River, and an open 
river reach on the Mississippi River near Cape Girardeau, MO.  These six RTAs 
were chosen to represent the range of conditions present throughout the UMRS and 
are meant to allow for system wide inferences about fish population and 
community dynamics.  To test the adequacy of these six RTAs in representing the 
variation of fish communities present in the UMRS, additional sampling was 
conducted during 2000 from areas above and below (out-pools) three RTAs, and 
from navigation pools 19 and 20.  Cluster analysis and non-metric multi-
dimensional scaling of species composition (presence absence) and community 
structure data revealed two major spatial groups of pools, and four sub-groups.  
Northern and southern pools formed the two major pool groups.  The sub-groups 
identified included open river reaches, southern pools, northern pools, and the 
La Grange reach of the Illinois River.  Out pools generally grouped with the 
closest RTA, but pools 19 and 20 grouped with southern pools in terms of species 
composition with northern pools in terms of community structure.  This analysis 
suggests the six RTAs may be adequate to capture the major spatial differences 
in fish communities within the UMRS, namely southern versus northern pools, but 
additional research is needed to clarify how fish communities in pools 19 and 20 
contrast with other areas in the UMRS.  

Keywords:  Upper Mississippi River System, fish communities, spatial variation, 
multivariate statistical analysis