Scaphirhynchus Conference: Alabama, Pallid, and Shovelnose Sturgeon

St. Louis, Missouri, 11-13 January 2005

12.  PHYSICAL AND HORMONAL EXAMINATION OF MISSOURI RIVER SHOVELNOSE STURGEON REPRODUCTIVE STAGE

Mark L. Wildhaber, U.S. Geological Survey, Columbia Environmental Research Center, 4200 New Haven Road, Columbia, Missouri 65201; Phone 573-876-1847; FAX 573-876-1896; mwildhaber@usgs.gov

Diana M. Papoulias, U.S. Geological Survey, Columbia Environmental Research Center, 4200 New Haven Road, Columbia, Missouri 65201; Phone 573-876-1901; FAX 573-876-1896; ppapoulias@usgs.gov

Aaron J. DeLonay, U.S. Geological Survey, Columbia Environmental Research Center, 4200 New Haven Road, Columbia, Missouri 65201; Phone 573-876-1878; FAX 573-876-1896; adelonay@usgs.gov

Donald E. Tillitt, U.S. Geological Survey, Columbia Environmental Research Center, 4200 New Haven Road, Columbia, Missouri 65201; Phone 573-876-1886; FAX 573-876-1896; dtillitt@usgs.gov

Janice L. Bryan, U.S. Geological Survey, Columbia Environmental Research Center, 4200 New Haven Road, Columbia, Missouri 65201; Phone 573-441-2953; FAX 573-876-1896; jbryan@usgs.gov

Mandy L. Annis, U.S. Geological Survey, Columbia Environmental Research Center, 4200 New Haven Road, Columbia, Missouri 65201; Phone 573-441-2940; FAX 573-876-1896; mannis@usgs.gov

Management of sturgeons requires information on reproductive physiology and the influence of environmental variables on sexual maturation and spawning.  Field assessment of reproductive success in sturgeons is difficult due to the generational length of the species, limited experimental data, and the general challenges of sampling in large rivers.  The shovelnose sturgeon (Scaphirhynchus platorynchus), endemic to the Missouri and Mississippi Rivers, is one of the few species of sturgeon that is not currently listed as threatened or endangered.  To keep shovelnose sturgeon populations viable and help in recovery efforts of other sturgeons methods must be developed that permit study and monitoring of shovelnose sturgeon reproductive changes that are non-lethal and minimally stressful.  Concomitantly, sturgeon reproductive hormones are controlled by numerous environmental and biological stimuli such that concentrations of the hormones will vary with reproductive stage of development, age and season.  Therefore, a complimentary suite of endocrine measures is needed to clearly differentiate stage of gonadal development.  To address these goals, in May 2001 we began year-round field sampling of Lower Missouri River shovelnose sturgeon to develop methods for determination of gender and the reproductive stage of sturgeons in the field.  On a monthly basis ultrasonic and endoscopic imagery and blood samples were collected.  These data were used to develop monthly reproductive stage profiles for shovelnose sturgeon that could be compared to data collected on pallid sturgeon.  The data were used to cross-validate multiple indicators that define gender and stage of gonad development.  The temporal scale of this study also resulted in a set of reference data that can be used to visually and hormally identify the gender and reproductive state of shovelnose sturgeon.  The data presented include plasma concentrations of sex steroids, gonad-somatic index, and histologic, ultrasonic, and endoscopic examination of gonads.  These data provide a baseline for annual cycles of metrics for assessment of reproductive status in shovelnose sturgeon.