TWENTY-FIFTH ANNUAL EASTERN FISH HEALTH WORKSHOP MARCH 10-13, 2000   Ulcerative Dermatitis In Striped Bass: An Evaluation Of The Condition At The Population Level     Eric B. May1, Anthony Overton1, Larry Pieper2, and Craig Weedon2   1Maryland Cooperative Fish and Wildlife Unit; University of Maryland Eastern Shore; Princess Anne, MD 21853; 2Maryland Department of Natural Resources; Matapeake Work Station, Stevensville, MD. 21683     Since 1994, striped bass (Morone saxatilis) have been affected with skin lesions or sores. Initially the outbreak occurred in the Potomac River near the mouth of the Wicomico River (West). Individual striped bass exhibiting such sores were, in 1994, examined and isolates of Edwardsiella tarda obtained in pure culture (Baya et al., 1997). Since this first report, isolates of Aeromonas sp., Pseudomonas sp, and Vibrio sp. have also been obtained in pure culture from striped bass similarly affected. In 1996 striped bass were found to exhibit sores typical of those seen before, however no consistent isolates could be obtained. In most cases where external sores were present, granulomas, suggestive of Mycobacteria sp. were seen grossly. Histological evaluations revealed granulomas typical of Mycobacterial infections, and acid fast staining confirmed the presence of acid fast positive organisms in the granulomas. In 1998, studies were initiated to examine the situation from two perspectives: first, are the skin lesions seen in striped bass indicative of a more fundamental problem related to the expanding population of this species in the Chesapeake Bay. Many feel that such increases outstrip the available forage base, the consequence of which results in fish infected by any number of opportunistic pathogens; or second do the infections in striped bass by Mycobacteria sp. represent a new or unusual epizootic which result in chronic infections leading to emaciation and the appearance of external sores.  This report will document gross, histological and morphometric information taken from over 200 live caught striped bass through out the Maryland portion of the Chesapeake Bay. Correlations have been made relating length/weight ratios, condition factors, and an index of infection. Based on the observations to date, there is no clear indiction that loss of forage base is related to infections of Mycobacteria sp., rather there is a clear indiction there other more subtle conditions operating.  This presentation will provide the current data, analyses and discussion of possible factors which are contributing to the situation with striped bass in the Chesapeake Bay.     Return to 25th Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page