SPATIAL AND TEMPORAL VARIATION IN THE RELATIVE ABUNDANCE OF UPPER MISSISSIPPI 
RIVER FISH SPECIES

Daniel J. Kirby1, and Brian S. Ickes2.
1 Iowa Department of Natural Resources, 206 Rose Street, Bellevue, Iowa, USA 
52031 
2 U.S. Geological Survey, Biological Resources Division, Upper Midwest 
Environmental Sciences Center, 575 Lester Avenue, Onalaska, Wisconsin, USA 54650

During 1993-2002, the Long Term Resource Monitoring Program used day 
electrofishing to make fish collections (N=3,324) within backwater, main channel 
border, and side channel aquatic areas at randomly selected sites in Pools 4, 8, 
13, and 26 of the Upper Mississippi River and the La Grange Pool of the Illinois 
River.  Electrofishing data were used to assess temporal and spatial variation 
in the relative abundance of fish species (N=50) common to all study areas 
(i.e., species that were captured in all five study areas during 1993-2002).  
Specifically this investigation focused on identifying the presence and relative 
importance of longitudinal-spatial (i.e., among study area), lateral-spatial 
(i.e., among aquatic area), and temporal (i.e., among year) variation in the 
proportion of positive electrofishing runs for each species.  Among groups 
variation at the study area, aquatic area, and year factor levels was measured 
as group sum of squares using a three-factor analysis of variance.  Principal 
components analysis and three-dimensional rotating plots were used to ordinate 
species based upon factor level and interaction term group sum of squares.  
These visual representations of longitudinal-spatial, lateral-spatial, and 
temporal variation in relative abundance can be used by fisheries managers to 
determine which fish species are most likely to exhibit a relative abundance 
response to local habitat modifications, climatic variability, or degradation of 
specific types of aquatic areas.

Keywords:  fish abundance, Mississippi River, spatial variation, temporal 
variation, fisheries management