In August 2016, a petition to list the Sturgeon Chub Macrhybopsis gelida and Sicklefin Chub Macrhybopsis meeki under the U.S. Endangered Species Act was presented to the U.S. Fish and Wildlife Service. Historically these two species were located throughout the Missouri River basin. Currently these two species have reduced to the lower main stem Missouri River and are considered rare throughout the tributaries within the basin. Several factors (i.e., habitat fragmentation, channelization, etc.) have likely contributed to these declines (Figure 1 & 2). Although concerns in the decline of these species have been considered in the past, little effort has been put towards better understanding the current status of these species within the river system. This information would be valuable in determining the ecological health of the Missouri River as well as provide crucial information needed for determining a listing outcome.
In addition to these two fish species several other species have been in decline throughout the Missouri River. For example, Flathead Chub have declined across much of the main-stem Missouri River in the Lower Basin. These fish species are crucial to the dynamic food web in the Missouri providing forage for many top predators like catfish Ictaluridae and sturgeon Acipenseridae species.Recent evidence has suggested that the endangered pallid sturgeon Scaphirhynchus albus has been in declining condition since 2011. This loss of condition in Pallid Sturgeon could be influenced by the loss in forage base. Adult Pallid Sturgeon are piscivorous and dependent on the small fish community to meet energy demands. Understanding if the loss of these forage species has influenced condition in Pallid Sturgeon is critical for the species recovery. Interception and Rearing Complexes (IRCs) are being engineered to help support juvenile Pallid Sturgeon reach shallow water rearing complexes in the Missouri River (Figure 3). The benefits of these complexes should extend beyond Pallid Sturgeon rearing sites and provide shallow water habitat for small fish in the main stem of the Missouri River. The importance of these IRCs for both Pallid Sturgeon and the surrounding fish community has been recognized by the current versions of the Science and Adaptive Management Plan (April 2018). Recently it was expressed that current monitoring plans of IRCs and Pallid Sturgeon demographic monitoring will not include a fish community assessment (PSPAP 2.0). It is crucial to understand the current status of these fish communities in the Missouri River and how these fish communities change from past studies and with construction of IRCs.
