Document Type



Virginia Institute of Marine Science

Publication Date



2004 was the second very wet year in a row. While rainfall and streamflows were normal in winter and early spring, and just slightly above average during the summer, the fall of 2004 was nearly as wet as the year before. Salinities were again depressed throughout the lower Bay. Water temperatures were below normal during the winter, but typical otherwise. Low salinities and, in the winter, temperatures brought continued abatement in the oyster diseases caused by Perkinsus marinus (Dermo) and Haplosporidium nelsoni (MSX). Among quarterly James River Survey sites, maximum annual P. marinus prevalences were the lowest they had been since before 1992. In summer and fall, when P. marinus is normally most prevalent, it was found in a maximum of 68% of oysters at Wreck Shoal and in no more than 20% of the oysters anywhere else. Advanced infections were rare, and limited to Wreck Shoal. H. nelsoni was found in a single oyster, at Wreck Shoal in July.



American Oyster Diseases, Chesapeake Bay, Virginia