Thesis (M.S.)--Tennessee Technological University, 2009. / Title from title page screen (viewed on Jan. 29, 2010). Includes bibliographical references.

Thesis (MS)--Montana State University--Bozeman, 2009. / Typescript. Chairperson, Graduate Committee: Christopher S. Guy. Includes bibliographical references (leaves 64-72).

Thesis (M.S.)--Montana State University--Bozeman, 2005. / Typescript. Chairperson, Graduate Committee: Christopher S. Guy. Includes bibliographical references (leaves 55-62).

Stock assessment and behavioral studies are needed to identify habitat use and population dynamics of endangered pallid sturgeon Scahphirhynchus albus in the freelowing lower Mississippi River; however, effective sampling methods have not been evaluated. Trotlines and otter trawls were consequently fished year-round to determine the more effective gear and to determine effects of environmental variables on catch rates. Trotlines were more effective for catching large (> 600 mm FL) pallid sturgeon and neither gear was effective for catching small (100-600 mm FL) pallid sturgeon. Greater predicted probabilities of catching large pallid sturgeon with trotlines were in 9-19 °C water temperatures, 0.7-0.9 m s-1 surface current velocities, and in greater depths (up to 12 m). Results of this study provide information that can be used to maximize sampling efficiency.

The habitat requirements of shovelnose sturgeon populations are unknown for the lower Mississippi River. Active acoustic telemetry was used to measure temporal variation in habitat use of shovelnose sturgeon and preference for depth, surface current velocity, and riverbed rugosity and slope by the population and within sandbar microhabitats. Shovelnose sturgeon occupied habitats differently throughout the year; and, within habitats, areas of moderate depth and surface current velocity and smooth riverbed were preferred. Within sandbars, environmental conditions did not differ from the surrounding environment, yet frequent aggregations of individuals in the lower portion of sandbars often in close proximity suggest habitat preference at a scale greater than the 5 ha measured. Results of this study provide information on seasonal habitat use patterns and methods that can be applied to a long-term dataset to identify the habitat requirements of shovelnose sturgeon.

Shovelnose Sturgeon patterns of movement are unknown for the lower Mississippi River. Active acoustic telemetry was used to determine how Shovelnose Sturgeon moved throughout a section of river and what influenced those movements. Distance to habitat type, depth, surface current velocity, river stage, change in river stage, river bottom slope, and temperature were investigated. Shovelnose Sturgeon were found not to have random or goal-oriented movements using a straightness index. Movement rate was influenced by river stage and surface current velocity. Habitat suitability changed with river stage and distance to habitat type supported a suite of delineated river features that Shovelnose Sturgeon use at different river stages. Results of this study provide movement and selection methods that can be applied to a long-term dataset to identify movement characteristics of Shovelnose Sturgeon in the lower Mississippi River.

Growth rates and diet patterns for sympatric pallid sturgeon Scaphirhynchus albus and shovelnose sturgeon S. platorynchus throughout the Missouri River and lower Mississippi River were examined. Pallid sturgeon growth in the Great Plains Management Unit (GPMU) was slower than in other river reaches until age 9 and pallid sturgeon from the Interior Highlands Management Unit (IHMU) and Coastal Plain Management Unit (CPMU) did not differ. No differences in growth between management units were detected for shovelnose sturgeon. Observed differences in growth between pallid sturgeon and shovelnose sturgeon were generally dependent upon which growth model was used, but pallid sturgeon were typically larger after age 4. Diet is considered a primary driver of growth. Stable isotopes are capable of examining diet over longer time periods than gut content studies, but that time frame is dependent on which tissue is selected. Using fin clips, diet of both pallid sturgeon and shovelnose sturgeon was evaluated via stable isotopes. Pallid sturgeon and shovelnose sturgeon trophic position (TP) was influenced by management unit. There was a slight, but not significant, latitudinal trend with pallid sturgeon TP increasing by approximately one full TP between the GPMU and CPMU. Pallid sturgeon growth was negatively related to TP but was unrelated to δ13C in the Missouri River. Shovelnose sturgeon growth was not related to TP, but was negatively related to δ13C in the Missouri River. Dissimilarity in TP combined with differences in δ13C between species suggests low diet overlap between these sympatric species, and neither species should be used as a surrogate for the other for prey consumption studies. Further, pallid sturgeon differences between the GPMU and the rest of the management units suggest that individuals from the GPMU could be managed separately from those in other management units.