Causes of Decreased Migrant Waterfowl use in Part of the Upper Mississippi River Wildlife and Fish Refuge

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Date
1976Author
Andersen, Mark Leonard
Publisher
University of Wisconsin-Stevens Point, College of Natural Resources
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Show full item recordAbstract
This study was designed to determine the causes for decreased
migrant waterfowl use in the Weaver Bottoms of Mississippi River pool
five. Spring Slough, in pool seven, was selected as a control.
Vegetation was sampled on square foot plots. The species present
and their respective abundances were determined. These were related to
depth, clarity and substrate type. Chemical parameters of the water
also were determined.
Vegetation type maps and waterfowl censuses made during this study
were compared to those made at intervals since impoundment created this
habitat in the late 1930's.
Lessened waterfowl use was due to a pronounced decrease in the
abundance of aquatic macrophytes which supplied food for waterfowl.
The amount and variety of vegetation declined as a result of greatly
accelerated successional changes. The depth, size and openess of the
Weaver Bottoms allowed winds to uproot vegetation and increase turbidity.
Water flow patterns through the area were altered by the deposition of
dredge spoil by the u.s. Army Corps of Engineers since 1940.
Much of the vegetation was dislodged by severe wind action by late
July during this study. Exclosures designed to test the effects of
carp on vegetation showed no significant difference between areas with
and without carp.
Measures for rehabilitating the Weaver Bottoms were suggested. The
best methods would be complete or partial filling of selected areas
combined with construction of islands to decrease wave action and a
partial closing dam at the downstream end to increase sedimentation and
raise the river bottom. Water flow could be reduced by closing openings
to the main channel. Most of the remedial measures would use large
quantities of previously unwanted dredge spoil. Spoil would be capped
with silt or topsoil to insure rapid vegetation growth.