Influence of a high-head dam as a dispersal barrier to fish community structure of the Upper Mississippi River

River Research and Applications
By: , and 



In river systems, high‐head dams may increase the distance‐decay of fish community similarity by creating nearly impermeable dispersal barriers to certain species from upstream reaches. Substantial evidence suggests that migratory species are impacted by dams, and most previous studies in stream/river networks have focused on small streams and headwaters. Here, we assess whether a high‐head dam (Lock and Dam 19; LD 19) on a large river, the Upper Mississippi River (UMR), substantially alters fish community structure relative to variability expected to occur independent of the dam's effect as a fish dispersal barrier. Using fish catch per unit effort data, we modelled the distance‐decay function for the UMR fish community and then estimated the similarity that would be expected to occur across LD19 and compared it with measured similarity. Measured similarity in the fish community above and below LD19 was close to the expected value based on the distance‐decay function, suggesting LD19 does not create an abrupt transition in the fish community. Although some migratory fish species no longer occur above LD19 (e.g., skipjack herring, Alosa chrysochloris), these species do not occur in high abundance below the dam and so do not drive variation in fish community structure. Instead, much of the variation in species structure is driven by the loss/gain of species across the latitudinal gradient. Lock and Dam 19 does not appear to be a clear transition point in the river's fish community, although it may function as a meaningful barrier for particular species (e.g., invasive species) and warrant future attention from a management perspective.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Influence of a high-head dam as a dispersal barrier to fish community structure of the Upper Mississippi River
Series title River Research and Applications
DOI 10.1002/rra.3534
Volume 36
Issue 1
Year Published 2020
Language English
Publisher John Wiley and Sons, Inc.
Contributing office(s) Upper Midwest Environmental Sciences Center
Description 10 p.
First page 47
Last page 56
Country United States
State Illinois, Iowa Minnesota, Missouri, Wisconsin
Other Geospatial Upper Mississippi River
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