EVIDENCE FOR HABITAT LIMITATION OF CENTRARCHID FISHES OVER A BROAD SPATIAL SCALE 
IN THE UPPER MISSISSIPPI RIVER SYSTEM

Steve Gutreuter
US Geological Survey, Upper Midwest Environmental Sciences Center, 2630 Fanta 
Reed Road, La Crosse, WI 54603

Habitat rehabilitation efforts are typically costly, and will be ineffective if 
habitat is not limiting.  Therefore, it is important to assess habitat 
limitation wherever habitat rehabilitation projects are considered.  Catch-count 
data from the Long Term Resource Monitoring Program were used to identify 
evidence for backwater habitat limitation by centrarchid fishes in the Upper 
Mississippi River System.  The data were collected using a probability-based 
stratified-random sampling design.  The design enabled fitting statistical 
models of the association between mean catch at the spatial scale of tens of 
river kilometers and the percentage of contiguous aquatic area in backwater of 
various minimum depths by maximizing a stratum-area weighted negative binomial 
log likelihood function.  The results were consistent with the hypothesis that 
backwaters limit the abundance of centrarchids in this large river system, but 
only when backwaters composed very small percentages of the total contiguous 
aquatic area.  This suggests that habitat restoration projects designed to 
increase the area of backwaters suitable for winter survival of centrarchids in 
the Upper Mississippi River System will be likely to produce measurable benefits 
only in the lower reaches of that system where backwaters are presently 
uncommon.  Predictions from these statistical models can be validated in situ if 
backwater areas are changed by habitat restoration and sedimentation, and if the 
resulting changes in bathymetry can be updated at appropriate time intervals.

Keywords: centrarchid fishes, backwaters, habitat, limitation, model
16


3