TRENDS OF VALLISNERIA AMERICANA ON THE UPPER MISSISSIPPI RIVER, POOL 7, LAKE 
ONALASKA CLOSED AREA


Amy Papenfuss1,2  1U.S. Fish and Wildlife Service, Upper Mississippi River 
National Wildlife & Fish Refuge - La Crosse District, Onalaska, WI 54650  2St. 
Mary's University of Minnesota - Winona Campus, Winona, MN 55987

Vallisneria Americana, commonly called wildcelery, is submersed aquatic 
vegetation that serves as an important food source for migrating canvasback.  
Collected samples from the early 1980's indicate that Vallisneria was abundant 
throughout Lake Onalaska.  Wildcelery and other aquatic vegetation densities 
dropped severely following the 1988 drought.  Since 1989, wildcelery populations 
have slowly regained vigor on Lake Onalaska, a historical migratory point for 
canvasback.  This study analyzes the trends of the wildcelery within a closed 
hunting zone on Lake Onalaska from 1980 to 2001, excluding a few years not 
sampled in the late 1980's. Water depth, percent vegetation cover and wildcelery 
density were monitored on twelve 800-meter transects, each comprised of 10 
sample points.  In addition to the field-evaluation, vegetation on infrared 
aerial photographs was also used in the analysis.  Submersed vegetation from 
photos was delineated and converted into a usable GIS form.  The results for the 
field samples and the interpreted photos were overlaid to compare and identify 
the locations of the wildcelery.  Additional comparisons were made between the 
1998-bathometric data and the water depth recorded from the annual surveys.  
Preliminary results indicate that the extent of wildcelery on Lake Onalaska can 
be predicted from the water depth/density relationships. Of course other factors 
such as water chemistry greatly affect the presences of submersed vegetation.