FACTORS AFFECTING FISH HABITAT DURING PERIODS OF ICE
COVER ON THE UPPER MISSISSIPPI RIVER.

James R. Fischer1, David M. Soballe2, and James T. Rogala2
1Wisconsin Department of Natural Resources, Onalaska, Wisconsin 54650,
2U.S. Geological Survey, Long Term Resource Monitoring Program, Onalaska,
Wisconsin 54650.

Overwintering conditions for centrarchid fishes in backwaters of the Upper
Mississippi River System (UMRS) are a primary concern to river managers, but
relatively few data have been collected to describe winter habitat conditions and
factors that affect them.  Winter limnological data have been collected on
several study reaches of the UMRS for the Long Term Resource Monitoring
Program since 1994.  Results of stratified random sampling show that winter
conditions are highly variable and that 'ideal' habitat conditions are rare, with
temperature, depth, dissolved oxygen, and velocity all limiting the amount of
suitable overwintering habitat.  During the winters of 1996 and 1997, spatially
and temporally intense sampling documented the effects of minor water level
fluctuations on dissolved oxygen and temperature.  Additionally, it appears that
bathymetric structure in some backwaters may play a role in how the backwaters
respond to changes in river elevation.  While further study is required to clarify
the role that bathymetry plays in backwater response, it is possible that
overwintering conditions in some backwaters may be improved by a
combination of (1) water level manipulation and (2) small scale habitat projects
with bathymetry as the primary focus.

Keywords: winter, centrarchid, dissolved oxygen, water level, Mississippi River


Presenting author information:
James R. Fischer, Wisconsin Department of Natural Resources, 575 Lester
Avenue, Onalaska,
Wisconsin 54650; (608) 783-7550; FAX (608) 783-8058;
Jim_Fischer@usgs.gov)

Preference: Poster
Convert?: No
Status: Professional