Scaphirhynchus Conference: Alabama, Pallid, and Shovelnose Sturgeon

St. Louis, Missouri, 11-13 January 2005

7.  IDENTIFICATION OF SCAPHIRHYNCHUS ALBUS, S. PLATORHYNCHUS, AND S. ALBUS x S. PLATORHYNCHUS HYBRIDS USING MORPHOLOGICAL CHARACTERS.

Bernard R. Kuhajda*, Department of Biological Sciences, University of Alabama, Box 870345, Tuscaloosa, AL 35487-0345; Phone 205-348-1822; FAX 205-348-6460; bkuhajda@bama.ua.edu

Richard L. Mayden, Department of Biology, Saint Louis University, 3507 Laclede Avenue, St. Louis, MO 63103-2010; Phone 314-977-3494; FAX 314-977-3658; maydenrl@slu.edu

Robert M. Wood, Department of Biology, Saint Louis University, 3507 Laclede Avenue, St. Louis, MO 63103-2010; Phone 314-977-3904; FAX 314-977-3658; wood2@slu.edu

Potential hybridization between the endangered pallid sturgeon, Scaphirhynchus albus, and the sympatric shovelnose sturgeon, S. platorynchus, has been reported within the Mississippi and Missouri rivers, with most purported hybrids from the lower Mississippi River Basin.  Because no studies have examined the extent of morphological variability within either species in the lower basin, identification of hybrids is problematic.  Principal components analysis (PCA) has been a useful tool in differentiating between these parental species and known hybrids from the upper Missouri River; all commonly-used character indices fail to separate these species/hybrids.  Within the lower Mississippi River Basin, S. albus is much smaller compared to upstream populations and is more difficult to discern from S. platorynchus.  Hybridization is reportedly more common and back-crossing of hybrids with parental species is a concern.  All of these factors make Lower Basin Scaphirhynchus more difficult to differentiate than specimens from the Missouri River Drainage.  Morphometric data analyzed with PCA from photo-vouchers of released specimens are somewhat useful in differentiating between these two sturgeon species and their hybrids, but some characters (i.e., barbels) are difficult to measure accurately.  Use of qualitative characters from photo-vouchers may aid in accurate identification.  Proper specimen identification is essential for researchers to collect valid data useful in the management of the endangered pallid sturgeon.