AUTHORS: Hannah Lenning, Iowa Department of Natural Resources/University of Nebraska at Kearney; Melissa Wuellner, University of Nebraska at Kearney; Seth Fopma, Iowa Department of Natural Resources; Keith Koupal, Nebraska Game and Parks Commission; Jayne Jonas-Bratten, University of Nebraska at Kearney
ABSTRACT: This research evaluates the impacts of restoring backwaters, a habitat type in large floodplain rivers that are essential for maintaining their high diversity of fauna. The restoration of backwaters has been an integral part of managing fish populations on the Upper Mississippi River since 1990 and is a major component of the Upper Mississippi River Restoration Program. This research looks at a 2013 restoration project that expanded on the traditional approach by restoring multiple backwaters in a single effort, resulting in 63 acres of backwater channels dredged within four backwaters, proximal in space (within 14-km reach) and time (2013-2017). Here, we evaluated whether benefits of restoration (increased catch or shifts in size structure) are observed beyond project boundaries and identified species that are indicators of backwater restoration, comparing two river reaches using a BACI approach. The river reach containing restored backwaters (Pool 12) is the Impact area, and a downstream river reach without restored backwaters (Pool 13) is the Control area. Historical, day electrofishing data was utilized, with the before period including sampling years prior to any construction (2006 – 2012) and the after period including years after construction concluded (2018 – 2024). For representative species, relative abundance was compared using the Kruskal-Wallis test. Nonmetric multidimensional scaling (NMDS) was conducted to visualize the similarities and differences between fish assemblages of each BACI group. Finally, indicator species analysis was conducted on each BACI group, which identified indicators of river reaches with and without this approach to backwater restoration. Understanding the scalar impact of Pool 12 restoration and its impact on fish assemblages informs the future planning of restoration projects to maximize program resources and efficiency.
