Genetic Management Plan For The Endangered Pallid Sturgeon Scaphirhynchus Albus Captive Broodstock Mantained Sic At Gavins Point National Fish Hatchery PDF Download

Pallid sturgeon (Scaphirhynchus albus) and shovelnose sturgeon (S. platorhynchus) are sympatric in the Missouri and Mississippi Rivers. Pallid sturgeon are listed as endangered under the US Endangered Species Act, while shovelnose sturgeon are common enough to be commercially harvested in several states. It is not currently possible to distinguish these species due to morphological overlap between species and a lack of identified fixed genetic differences. This has undoubtedly had negative impacts on pallid sturgeon recovery efforts. The major focus of this dissertation was to use multiple microsatellite loci and morphological characters to accurately discriminate pallid and shovelnose sturgeon throughout their shared range and to examine intraspecific genetic variation across the geographic ranges of both species. Bayesian assignment testing based on microsatellite genotypes was used to determine the number of natural groups within Scaphirhynchus samples without identifying species a priori . The genetic analysis was then used in concert with morphological character index values to define pallid, intermediate, and shovelnose sturgeon. Once species were defined, the relationship among pallid and shovelnose sturgeon was tested and the intermediate individuals were analyzed to investigate hybridization. These analyses showed all pallid sturgeon are more closely related to each other than any were to shovelnose sturgeon, and found many of the intermediates were consistent with hybrid ancestry. Significant population structure was found in both species, with pallid sturgeon populations being more genetically differentiated than shovelnose sturgeon populations. Results indicate that local broodstock should be used for hatchery supplementation of pallid sturgeon in the recovery effort, and distinct shovelnose sturgeon populations may require individual management consideration. The microsatellite data were effective at parentage analysis in pallid sturgeon, and the data were also used to create a forensic tool that is capable of identifying unknown Scaphirhynchus specimens to species. Finally, comparing genetic species discrimination to morphological species discrimination showed that both methods are required to accurately identify all potential hybrid specimens. The results of this dissertation have already been presented to the pallid sturgeon recovery team, and are being incorporated in the pallid sturgeon recovery effort.