TWENTY-THIRD ANNUAL EASTERN FISH HEALTH WORKSHOP JOHN CARVER INN, PLYMOUTH, MA 30 MARCH - 2 APRIL, 1998 Overview Of The Fish Lesion/Toxic Dinoflagellate Problems In The Chesapeake Bay Vicki S. Blazer and Christine Densmore National Fish Health Laboratory, USGS/BRD, 1700 Leetown Rd, Kearneysville, WV 25430 Worldwide there has been a reported increase in frequency and severity of harmful algal blooms (HABs). Dinoflagellates contribute to these HABs with over 40 species verified as producing toxins. Pfiesteria and Pfiesteria-like dinoflagellates have received a great deal of popular press. Much of this interest has to do with the potential human health hazards. Available information about these organisms will be reviewed. In summer and fall of 1996 watermen began reporting a high incidence of fish with lesions in the Pocomoke River, MD. Reports began again in Spring 1997 and the state of MD began to collect fish from the Pocomoke as well as other affected tributaries. During the summer and fall of 1997 we collected a variety of fish species with and without lesions for histology and the findings will be reviewed. Pfiesteria piscicida or other toxic dinoflagellates were and continue to be blamed for these lesions. In Aug. two fish kills, primarily involving menhaden, occurred in the Pocomoke River and resulted in the river being closed for extended periods of time. In addition, the appearance of menhaden with lesions (although no major kills) lead to King's Creek off the Manokin River and the Chicamicomico River being closed. In water samples taken during the kills fairly high levels of dinoflagellates were observed and later shown to be toxic to fish. The relationship between presence of toxic dinoflagellates and fish lesions is tenuous at best, particularly where fish kills have not occurred. This session will review a variety of findings by MD state and USGS personnel.   Return to 23rd Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page