Amoebic Gill Disease In Pallid Sturgeon, Scaphirhynchus albus       Kathleen P. Hughes1, Stephen A. Smith1 and James Luoma2   1Aquatic Medicine Laboratory, Department of Biomedical Sciences and Pathobiology, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061 USA; 2USFWS, Garrison Dam National Fish Hatchery, Riverdale, ND 58565 USA     A federal hatchery raising endangered freshwater pallid sturgeon (Scaphirhynchus albus), experienced high mortality rates in their fingerling (1.5 - 2.0 grams) stock in late summer of 2000. The sturgeon had been hatched the previous spring, and were presently being reared at 17-18o C. The hatchery water source was an open supply coming from a reservoir supplied by the Missouri River. Other species of fish maintained at the facility included salmonids (coho salmon, cutthroat trout, brown trout, and rainbow trout), walleye and northern pike. A sample of the affected population was sent to the Aquatic Medicine Laboratory of the Virginia-Maryland Regional College of Veterinary Medicine for diagnostic evaluation.  Gross external examination revealed healthy looking fish with slightly pale, clumped gills. Biopsies of gill tissue revealed excessive mucus coverage, but no obvious bacteria or external parasites were observed.  Bacterial cultures taken from the posterior kidney yielded moderate growth of a mixed bacterial infection.  Histopathological results showed severe epithelial hyperplasia and lamellar fusion of the gill tissue.  A parasitic infestation of an amoeba was also detected in histology of the gill tissue with the majority of the parasites concentrated on the gill surface in areas of severe epithelial proliferation.  Specific identification of the amoebae parasite was not attempted. To our knowledge, this is the first report of amoebic gill disease in sturgeon.