SPATIAL STRUCTURE AND TEMPORAL VARIATION OF FISH COMMUNITIES IN THE UPPER 
MISSISSIPPI RIVER.

John H. Chick1, Brian Ickes2, Mark A. Pegg3, Valerie A. Barko4, Robert A. 
Hrabik4  and David P. Herzog4
1Illinois Natural History Survey, Great Rivers Field Station, 8450 Montclair 
Ave, Brighton, IL 62012.  2U.S. Geological Survey, Upper Midwest Environmental 
Sciences Center, 2630 Fanta Reed Road, La Crosse, WI 54603.  3Illinois Natural 
History Survey, Illinois River Biological Station, 704 North Schrader, Havana, 
IL 62644.  4Missouri Department of Conservation Open River Field Station, 3815 
E. Jackson Blvd., Jackson, MO 63755.

We used data from Long Term Resource Monitoring Program collected from 1994 to 
2002 to assess variation in community composition and structure of Upper 
Mississippi River fishes.  Community composition of fishes varied more in space 
than through time, and we found substantial variation in community composition 
at two spatial scales: large scale differences between upper and lower river 
reaches, and small scale differences among individual regional trend areas 
(RTA).  Community structure of fishes (catch per unit effort) also varied more 
through space than through time.  We found substantial variation in fish 
community structure at three spatial scales: 1) large scale differences between 
upper and lower river reaches, 2) differences among individual RTA, and 3) 
differences among habitat strata, with backwaters having a distinct community 
structure relative to the main channel and side channels.  When averaged across 
all RTA, fish community structure in 1994 and 1995 was distinct from all other 
years, possibly as a result of the 1993 flood.  We found a significant Mantel 
correlation between fish community structure observations for each RTA and year, 
with the environmental variables measured during the collections.  A canonical 
approach revealed that the greatest correlation with community structure 
occurred for the combination of secchi depth, water temperature, water velocity, 
and vegetation abundance.  

Keywords:  fish communities, Upper Mississippi River, spatial variation, 
multivariate analysis, 1993 flood