A Fork in the Road

Pallid sturgeon biologists have long hypothesized that the areas where tributaries come together and flow into the Missouri River may hold significant value to species (see previous post “Where Are You When I’m Not Looking”).  The USGS Comprehensive Sturgeon Research Project biologists spent several months summarizing their data on pallid sturgeon habitat use collected between 2008 and 2011 to try and assess whether the confluence of the Osage River may be a significant habitat area.  The area they focused on was defined as 0.2 miles upstream and 0.6 miles downstream of the Osage River confluence on the main stem of the Missouri River (river miles 130.3 to 129.5).

Multibeam imagery and pallid sturgeon telemetry locations in and around the Osage River confluence area between May 2008 and November 2011.

Between May 2008 and November 2011, twelve telemetry-tagged pallid sturgeon were located 93 times in the Osage River or at its confluence with the Missouri River.  Telemetered pallid sturgeon have moved up the Osage River as far as Lock and Dam 1 (Osage river mile 12), and have remained in the tributary from spring through early fall. Pallid sturgeon were located in the Missouri River near the confluence in all seasons with individual sturgeon residing near the mouth of the Osage River for periods ranging from months to more than a year.

Locations of telemetered pallid sturgeon in the Missouri River between river miles 143 and 125 and in the Osage River from Lock and Dam 1 (Osage river mile 12) to the Missouri River confluence, 2008 - 2011.

Half of the twelve telemetry-tagged pallid sturgeon located in the Osage River confluence area are females with two or more locations in the vicinity.  One of these females was originally tagged in 2007, one in 2008, and four in 2010.  The female tagged in 2007, PLS07-011, was recaptured in March of 2008 at Missouri river mile 680.4 before taking up residence hundreds of miles downstream at the mouth of the Osage River. In contrast, a female originally tagged during 2008 in the Osage River confluence area, PLS08-058, spent nearly three years in the area before moving downstream in spring/summer 2011 (see previous post “River Sweep February 22 – March 4, 2011”).  Clearly pallid sturgeon are using the confluence area near the Osage River, and will travel some distance up the Osage River during spring and summer.  The Missouri Department of Conservation and the U.S. Fish and Wildlife Service routinely sample the area when searching for possible broodstock for the hatchery propagation program.  Unfortunately, none of the telemetry-tagged females located in or near the Osage River were in reproductive condition and present during the spawning period.  CSRP biologists have been unable to determine if spawning is occurring in the Osage River.  However, the willingness of pallid sturgeon to use the Osage River, to remain in the confluence area for extended periods of time, and to return to the area after travelling many miles upstream or downstream in the Missouri River suggests that the area may be significant and have value to the species.  Observations of pallid sturgeon near the Platte River in Nebraska suggest that sturgeon behave similarly there.  Why and under what conditions pallid sturgeon use Missouri River tributaries may provide important insight into the recovery needs of the species.

Biologists shared their results with other agencies and universities at the Midwest Fish and Wildlife Conference in Dec. 2011 in Des Moines, IA.

See previous posts to watch DIDSON footage of sturgeon at Lock and Dam 1 on the Osage River (“Trotlines and DIDSON find Pallid Sturgeon in the Osage River at Lock and Dam 1”) and for more information on the multibeam mapping conducted at the confluence of the Osage and Missouri rivers (“Drift and Retention of Sturgeon Larvae“).

By Emily Pherigo and Aaron DeLonay

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