The pallid sturgeon (Scaphirhynchus albus) is a critically endangered species native to the Missouri and lower Mississippi River drainages. Throughout their entire range, pallid sturgeons co-occur with shovelnose sturgeon (S. platorynchus) a species that is morphologically very similar and far more numerous. There is a considerable amount of morphological overlap between the two species and it has been suggested that morphologically intermediate forms may be hybrids (in the picture on the left the top fish is a shovelnose sturgeon and the bottom fish is a pallid sturgeon). While pallid sturgeon is federally protected, shovelnose sturgeon is commercially and recreationally harvested in several states including Illinois. Critical to the conservation of shovelnose sturgeon is the development of tools to distinguish between pallid sturgeon, shovelnose sturgeon, and hybrids if they exist.
Aaron Schrey (Ph.D. 2007, right) scored DNA microsatellite loci as a means of genetically discriminating between pallid and shovelnose sturgeons. Multilocus genotypes of sturgeons collected from the Middle Mississippi River (between Cairo Illinois and the confluence of the Missouri River) cluster into two discrete groups that are largely concordant with morphological identification of specimens (graph, lower left). These data indicate that pallid and shovelnose sturgeons from the Middle Mississippi River are reproductively isolated. Ongoing research includes a study of genetic structure of both species throughout their ranges (right) and a development of SIngle Nucleotide Polymorphism (SNP) loci for more efficient discrimination of larval sturgeons. This research is funded through the US Fish and Wildlife Service, the Army Corps of Engineers St. Louis District, and USGS.
