Variation in community composition (presence/absence data) and structure
(relative abundance) of Upper Mississippi River fishes was assessed using
data from the Long Term Resource Monitoring Program collected from
1994 to 2002. Community composition of fishes varied more in space than
through time. We found substantial variation in community composition
across two spatial scales: large-scale differences between upper and lower
river reaches and small-scale differences among individual regional trend
areas (RTA). Community structure (relative abundance data) of fishes 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. Fish community structure observations for each RTA and year
correlated with the environmental variables measured at each sample site.
A canonical approach revealed that the combination of Secchi depth, water
temperature, current velocity, and vegetation abundance had the greatest
correlation with community structure.
