Missouri River Macroinvertebrate Study
Field work began in 2005 for a 2-year project assessing summer macroinvertebrate assemblages and densities in the Missouri River below Fort Randall and Gavins Point dams. This project is the focus of SKEP student, Kristen Berg’s Master of Science research at South Dakota State University under the advisement of Drs. Robert Klumb (FWS) and Steven Chipps (USGS-SD Cooperative Fish and Wildlife Research Unit). Four randomly selected transects were sampled during each sampling period at three sites below Fort Randall and Gavins Point dams. Invertebrate assemblage composition and densities as well as substrate composition will be compared between the Fort Randall and Gavins Point sites as well as comparing upstream to downstream areas within each site. Habitats sampled included inside bends, outside bends, secondary connected channels, channel crossovers, and braided areas. Sampling occurred on three occasions from June through October 2005 and will continue in April through October 2006. In addition to providing an updated survey of the macroinvertebrate assemblage in the Missouri River, this study provides current estimates of invertebrate prey available to juvenile pallid sturgeon stocked in the Missouri River as part of recovery efforts. This data on prey availability will be linked with pallid sturgeon diet composition and applied in bionenergetics modeling analyses of pallid sturgeon habitat quality and growth potential.
Multiple gears were used to sample aquatic invertebrates in shallow, deep, benthic, and pelagic habitats. In the main river channel benthic invertebrates were collected with a large ponar grab. Drifting invertebrates were collected in the water column and near the bottom in the main channel with a 0.5-m conical plankton net outfitted with a flow meter to measure the volume of water filtered. In shallow habitats, benthic invertebrates were collected using a surber sampler. To assess invertebrate colonization, Hester-Dendy invertebrate plate samplers were deployed in the river for a 50-60 day colonization period. Additional habitat data collected during each sample included water temperature, depth, surface flow, turbidity, dissolved oxygen, and substrate type. Overall, 500 invertebrate samples were collected in 2005. As with the larval and juvenile fish surveys during 2003 and 2004, submersible temperature loggers were also deployed in the Missouri River downstream of Fort Randall (N = 14) and Gavins Point (N = 12) dams during 2005.
Although the motivation behind this macroinvertebrate survey was the determination of prey available to juvenile hatchery-reared pallid sturgeon Scaphirhynchus albus, a concurrent benefit of this project includes an active monitoring program for macroinvertebrate aquatic nuisance species, particularly zebra mussels. Active sampling of deep main channel benthos and placement of colonization plates in the Missouri River resulted in a spatially expansive monitoring program for zebra mussels in South Dakota and Nebraska. Although zebra mussel veligers have been identified in plankton samples from Lake Francis Case, SD and the Missouri River downstream of Fort Randall Dam (near Verdel, NE), no adult zebra mussels have yet been found. Extensive sampling, in upstream and downstream locations of the Missouri River below both dams will help elucidate the existence of adult zebra mussel populations.
No zebra mussel adults were observed downstream of Fort Randall and Gavins Point dams during the summer of 2005 in any ponar grab samples from the main channel or found colonized on Hester-Dendy artificial substrate invertebrate collection plates set near the bank line. The lack of evidence to date of an established population of zebra mussels in the Missouri River downstream of each dam indicates that either the initial veliger identifications were in error (i.e. a false positive) or that the source of the veligers was from populations in the deep waters of Lake Francis Case, habitats not sampled as part of this study. As in 2003 and 2004, no zebra mussels were observed during 2005 on the temperature loggers placed in the Missouri River downstream of each dam.
This project is primarily funded by a State Wildlife Grant from South Dakota awarded to Drs. Chipps and Klumb which started on July 1, 2005. However, the Great Plains FWMAO provided the necessary gear for collection of invertebrates (drift sampler, surber sampler, ponar), use of boats and trucks, had a custom boom built on the boat for the ponar dredge, portable meters (velocity, dissolve oxygen, turbidity) and assembled needed field supplies (preservatives, sample jars, etc.) to get the project started in early June. Additional funds were provided by the Aquatic Nuisance Species Task Force ($2500) to purchase the Hester-Dendy colonization samplers. Great Plains FWMAO staff provided field training (R. Klumb, Fisheries Biologist - 4 weeks) and field assistance (Steve Heutmaker, Biological Technician - 2 weeks) which will enable Kristen Berg to work safely and independently on this project during 2006.
