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Part I <br />INTRODUCTION <br />Hi for <br />Pallid sturgeon (Scaphirhynchus.albus)- evolved from an ancient group of bony <br />fishes, the subclass Paleopterygii, which was dominant during the Paleozoic <br />Era. This group continued to flourish through the late Paleozoic -Era and <br />early Mesozoic Era. Most species in this subclass became extinct sometime in <br />the Mesozoic Era. The living descendants of this group in North America <br />include paddlefish (Polyodontidae), and eight specie of sturgeon <br />(Acipenseridae). <br />The North American species of sturgeon, in addition to pallid sturgeon, are <br />the shovelnose sturgeon (Scaphirhynchus platorynchus Rafines'que); white. <br />sturgeon (Acipenser transmontanus Richardson); green sturgeon (Acipenser <br />medirostris Ayres); Atlantic sturgeon (Acipenser oxyrhynchus Mitchill); <br />shortnose sturgeon (Acipenser brevirostrum LeSueur); and 'lake sturgeon <br />(Acipenser fulvescens Rafinesque). An eighth species, the Alabama sturgeon <br />(Scaphirhynchus suttkus Williams), was recently described from the Mobile <br />Basin in Alabama and Mississippi (Williams and Clemmer 1991). This location <br />is outside the range of pallid sturgeon .and is not included in further <br />discussions of Scaphirhynchus species in this plan. <br />The pallid sturgeon was first described by S.A., forties and R.E. Richardson in <br />1905 from nine specimens collected from the Mississippi River near Grafton, <br />Illinois, in June 1904 (Forbes and Richardson 1905).. Known locally as the ; <br />white sturgeon, they named it Parascaphirhynchus albus and suggested it be <br />considered as its own genus. Later classifications, however, placed it in the <br />genus Scaphirhynchus where it has remained (Bailey and Cross 1954). <br />Electrophoretic analysis of the two species of Scaphirhynchus have suggested a <br />very close genetic relationship. Phelps and Allendorf (1983), using <br />electrophoretic techniques, were unable to distinguish the species by looking <br />at 3T enzyme systems. Pallid sturgeon from the Missouri River in Missouri and. <br />shovelnose sturgeon from the Missouri, Yellowstone, and Mississippi Rivers <br />were analyzed. The authors concluded that the close genetic similarity of <br />pallid sturgeon and shovelnose sturgeon was due i:o'recent or incomplete <br />reproductive isolation. <br />General Description: <br />Pallid sturgeon have a flattened, shovel-shaped snout; long, slender, and <br />completely armored caudal.. peduncle; :and lack a spiraclQ (Smith 1979). As with <br />other sturgeon, the mouth is toothless, protrusible, and ventrally positioned <br />under the snout. The skeletal structure is primarily cartilaginous (Gilbraith <br />et al. 1988) Pallid sturgeon are similar in appearance to the more common, <br />darker shovelnose sturgeon. Pflieger (1975) reports the principal features <br />distinguishing pallid sturgeon from shovelnose sturgeon are the paucity of <br />dermal ossifications on the belly, 24 or more anal fin rays, and 37 or more <br />dorsal fin rays. <br />1. <br />