T.R. Gemeinhardt

Age-0 Sturgeon Accessibility to Constructed and Modified Chutes in the Lower Missouri River

AbstractShallow-water habitat is hypothesized to provide nursery habitat for young fish. The construction of side-channel chutes to restore shallow-water habitat is common in the lower Missouri River; however, a recent adaptive management strategy document (developed by a multiagency, multidiscipline team), as well as previous research, has suggested that the accessibility of chutes to age-0 Scaphirhynchus spp. (sturgeon hereafter) may be limited. Access is a critical prerequisite for young fish utilizing chute habitat; thus, we investigated chute-specific accessibility for age-0 sturgeon at seven chutes (constructed and natural). Age-0 sturgeon were capable of accessing most chutes; however, accessibility appeared limited at sites with highly restrictive inlet structures. Our results suggest that future consideration of chute inlet designs that meet authorized Missouri River purposes while providing improved fish access is warranted. Additionally, capture sites for exogenously feeding age-0 sturgeon were...

Comparisons of zooplankton and phytoplankton in created shallow water habitats of the lower Missouri River: implications for native fish

Shallow water habitat (SWH) is important for riverine fish and their invertebrate prey, yet the availability of SWH has declined in many systems due to human impacts. We evaluated the potential ecological benefits of restoring SWH by comparing zooplankton and phytoplankton from created backwaters (a floodplain feature connected to the river on the downstream end but disconnected at the upstream end) and chutes (a side channel of the river that diverts flow from the main channel through the chute and back into the main channel) on the lower Missouri River. We tested the hypothesis that backwaters support higher abundances of zooplankton and phytoplankton than chutes using data that were collected during the summer of 2010. As predicted, backwaters had more diverse cladoceran communities and greater abundances of rotifers, copepod nauplii, adult copepods, and cladocerans than chutes. Total algal biovolume was the same in chutes and backwaters; however, phytoplankton taxa richness was higher in backwaters, and there was a greater biovolume of green algae (Chlorophyta), Crypotophyta, cyanobacteria, and Euglenophyta in backwaters than in chutes. Differences in zooplankton and phytoplankton between backwaters and chutes appeared to be related to slower current velocities, longer retention times, and lower levels of turbidity and total suspended solids in backwaters. While chutes have the potential to provide greater habitat diversity than the mainstem, there were no differences in water quality or phytoplankton abundance, community structure, or diversity between these two habitats. Combined, our results suggest that created backwaters initially provide a greater potential food resource for native fishes. However, additional research is needed to determine whether chutes can also develop beneficial shallow water features over a longer period of time.