Pallid sturgeon

     The reproductive and taxonomic status of pallid (Scaphirhynchus albus) and shovelnose (S. platorynchus) sturgeon remain in doubt.  In the past, identification of these species has been based strictly on morphology.  Several genetic studies have been unable to distinguish the two species or determine their reproductive status (Phelps and Allendorf 1983; Morizot 1994).  Although these species differ morphologically and occupy different ecological niches, it is not known whether they are reproductively isolated or if pallid sturgeon are simply a larger form of the shovelnose sturgeon.   Alterations to the pallid sturgeon’s preferred riverine habitat, such as damming and channelization, have been implicated in the recent decline of this species (Keenlyne 1989).  Natural reproduction has failed for at least one generation throughout most of the pallid sturgeon’s range (Montana Fish, Wildlife and Parks; www.fwp.mt.gov).  With the 1990 listing of the pallid sturgeon as endangered, it becomes imperative that the taxonomic and reproductive status of these two species is resolved in order to guarantee their continued protection.
      Pallid and shovelnose sturgeon were examined from the upper Missouri River, in Montana and the lower Mississippi (Atchafalaya River), in Louisiana where the two species occur sympatrically.  Two sites from the upper Missouri River were sampled; one site above Fort Peck Dam and another at the confluence of the Yellowstone and Missouri rivers.   Pallid and shovelnose samples were also collected from a single site on the Atchafalaya River, Louisiana,  including sturgeon morphologically identified as pallid-shovelnose hybrids.
      All samples were tested with 18 microsatellite primers to detect genetic differences.  Eleven microsatellites were cloned from lake sturgeon, Acipenser fulvescens (May et al. 1997) and seven from Atlantic sturgeon, A. oxyrhynchus oxyrhynchus (provided by Tim King, USGS-BRD).  All primers possessed tri- and tetra- repeat motifs.  Five of these loci were highly polymorphic having a range of 2 to 8 alleles.

      Keenlyne, K.D. 1989. A report on the pallid sturgeon. U.S Fish and Wildlife Service, Pierre, SD.  MRC-89-1. 20 pp.
      May, B.P., Krueger C.C., and H.L. Kincaid. 1997. Genetic variation at microsatellite loci in sturgeon: primer sequence homology in Acipenser and Scaphyrhynchus. Can. J. Fish. Aquat. Sci.
      Morizot, D.C. 1994. Scaphirhynchus final report. Genetic Analysis Inc. Smithville, Texas.
      Phelps, S.R. and F.W. Allendorf. 1983. Genetic identity of pallid and shovelnose sturgeon (Scaphirhynchus albus and S. platorhynchus). Copeia 1983: 696-700.