Sensitivity of Using Fin Rays for Shovelnose Sturgeon Age, Growth, and Dynamic Rate Functions

North American sturgeon have been intensively studied in recent years due to range-wide declines linked to anthropogenic disturbances such as habitat degradation, dam construction, and pollutants.  Shovelnose sturgeon Scaphirhynchus platorhynchus are the most widely distributed and abundant sturgeon species in North America, although many populations are in decline or are of unknown status.  Mortality, growth, and recruitment are three dynamic rate functions that typically describe the specific factors that influence fish abundance and biomass.  The methods used to estimate these dynamic rate functions all focus on the ability to accurately assign each fish to a particular age class, yet aging techniques have not yet been validated.  Our objective was to determine how variation in measuring growth patterns may affect specific dynamic rate functions.  Specifically, we evaluated known growth rates from recaptured individuals and also conducted a sensitivity analysis on how varying age estimates (ages allowed to randomly vary +/- 3 years) influence mortality and growth calculations.  Recaptured adult sturgeon displayed very little (i.e., 2-4 mm) annual growth, which was much lower than annual growth from back-calculation procedures indicated (i.e., 20-40 mm).   Our sensitivity analysis indicated that total annual mortality varied by as much as 21% across the various age scenarios evaluated.  These results will provide important implications as to how sturgeon populations are assessed in the future.