FISH PASSAGE THROUGH DAMS ON THE UPPER MISSISSIPPI RIVER.  

Daniel B. Wilcox 1, and Joseph H. Wlosinski 2.   1 St. Paul District,
U.S. Army Corps of Engineers, Environmental Resources Section,
190 5th Street East, St. Paul, MN 55101; 2 U.S. Geological Survey,
Upper Mississippi Environmental Sciences Center, 575 Lester
Drive, Onalaska, WI 54650.  

The Upper Mississippi River (UMR) is impounded by a series of 29
navigation dams which restrict fish movements in the river
system.  Design characteristics and operation of most UMR
navigation dams allow both upriver and downriver fish passage. 
Downriver fish passage can occur through the locks and the gated
sections of the dams.  Some fish may pass upriver through the
navigation locks, but the locks do not provide favorable pathways
for upriver fish passage.  Opportunity for upriver fish passage
is dependent upon hydraulic conditions at the dams, fish
behavior, and fish swimming abilities.  We examined historic fish
mark/recapture and telemetry data to identify fish species and
conditions under which fish pass through the dams.  We found
information on 126 UMR fish mark/recapture and telemetry studies
and were able to obtain at least some original data from 84 of
the studies.  Less than 10 percent of the marked fish were
recaptured.  Ten of the studied fish species were found to move
through at least one dam.  Of the 5,253 marked fish recaptured in
all studies, 87 percent were recaptured in the same pool where
marked, 8 percent moved upriver through at least one dam, and 5
percent moved downriver.  We examined head at the dams during
time periods when the marked fish were at large.  We could not
estimate the head during passage through dams for most of the
marked fish because of their long periods at large. We could
estimate the head within one foot for 68 of the marked fish that
moved through dams.  Of these, only five moved in a downriver
direction.  Of the 63 marked fish that moved upriver, 55 passed
through dams when the head was less than 0.3 m.  We investigated
hydraulic conditions through the dam gate openings using
information from a physical hydraulic model and with standard
hydraulic equations.  We reviewed the literature on migration
behavior and swimming performance of 25 migratory fishesin the
UMR.  Through analysis of the fish mark/recapture data, hydraulic
conditions at the dams, fish behavior and swimming performance
information, we estimated probability of opportunity for upriver
passage through UMR dams by different UMR adult fishes.  Most of
the UMR navigation dams present semipermeable barriers to upriver
passage, with fish passage opportunity varying markedly between
dams and fish species.  We identified the dams that present the
greatest barriers to fish passage.  Operational changes and
structural modifications at UMR navigation dams are possible and
may improve opportunity for fish passage throughout the UMR.  

Keywords:  fish passage, Mississippi River, dams, fish movement,
aquatic habitat