Latitudinal Variation in Juvenile Pallid Sturgeon

Restoration efforts for the federally endangered pallid sturgeon (Scaphirhynchus albus) have been largely targeted at population augmentation.  Recent studies  show that pallid sturgeon from the upper Missouri River are genetically distinct from fish found in the middle Missouri and lower Mississippi rivers, but it is not clear if  genetic differences are linked to physiological adaptation.  Pallid sturgeon populations inhabit a wide range of environmental conditions that might contribute to regional, physiological adaptations.   We obtained Age-0 pallid sturgeon from the upper and middle Missouri river basin, representing three families from each source population.  We measured routine metabolic rates (RMR; mg O₂/hour) of sturgeon using fiber optic oxygen probes (Neo Fox; Ocean Optics Inc.) at water temperatures ranging from 10-32⁰C.    Mean RMR was compared using a 2-way analysis of variance (ANOVA) with water temperature and parental source as grouping factors.  Initial results indicate that RMR does not differ between upper and middle basin pallids at an intermediate temperature of 15.4°C (p = 0.9).  We hypothesize that physiological adaptation between source populations will manifest at temperatures near the thermal optima (27°C) for pallid sturgeon.  Latitudinal variation in physiological adaptations of age-0 pallid sturgeon could have important effects on current stocking practices.