North vs. south: Thermal tolerance of two different stocks of shortnose sturgeon

The shortnose sturgeon (Acipenser brevirostrum) has been protected under the Endangered Species Act for nearly 4 decades, yet many populations have not recovered.  Although previous genetic analyses reveal significant latitudinal variation in stock structure, the ecological ramifications of these differences are unclear.  The objective of this study was to estimate the upper thermal tolerance of captive shortnose sturgeon cultured from two genetically distinct populations to identify potential differences in environmental tolerances of the different parent populations.  Hatchery reared shortnose sturgeon from both the Connecticut and Savannah populations, were evaluated in vitro to determine the LD50 in a controlled pair-wise experiment.  Our results showed that although heating rate was critically important in estimating LD50 of shortnose sturgeon, the two populations had significantly different thermal tolerances.  Future studies are needed to further evaluate stock specific differences in the environmental tolerances of shortnose sturgeon.