Scaphirhynchus Conference: Alabama, Pallid, and Shovelnose Sturgeon

St. Louis, Missouri, 11-13 January 2005

17.  EVALUATING SCHAPHIRYNCHUS SPAWNING SUCCESS: THE USE OF PHYSIOLOGICAL INDICATORS.

Diana M. Papoulias*, Aaron J. DeLonay, Mandy L. Annis, Donald E.Tillitt.   U.S. Geological Survey, Columbia Environmental Research Center, Columbia, Missouri, 65201; Phone 573-876-1902; FAX 573-876-1896; dpapoulias@usgs.gov 

The spawning grounds of Missouri River sturgeons have not been conclusively located. In a recent pilot project at CERC directed at identifying these areas, we evaluated the coupling of acoustic telemetry with measurements of stress, reproductive readiness, and spawning as tools to assess the annual spawning event.  March 2004, 30 gravid female shovelnose sturgeon were implanted with transmitters.  Concomitantly, blood and a gonad biopsy were collected.  The fish were tracked then, during July and August, nine fish were recaptured.  Upon recapture, a blood sample was again taken, the fish were necropsied, and a gonad sample preserved for histological examination.  Of the nine fish recaptured, seven had completely spawned, one did not spawn, and one did not spawn completely.  Cortisol levels were similar at both time points.  Biopsied eggs from all fish demonstrated germinal vesicle breakdown upon in vitro induction of maturation.  Polarization index (PI) of those fish that successfully spawned ranged from 0.08 to 0.12 and reproductive steroid levels were 1 to 2 orders of magnitude lower at recapture when compared to measurements in March.  Steroid levels and PI of those fish that were unsuccessful at spawning were anomalous by comparison.  These measurements are discussed with respect to fish behavior and environmental conditions during the spawning period.  The results of this preliminary investigation indicate that implantation of transmitters into gravid females does not prevent spawning, and that non-lethal physiological indicators may be used to evaluate spawning success.