Document Type



Virginia Institute of Marine Science

Publication Date



More normal riverflows and salinities returned in 2005 after two very wet years. Temperatures were somewhat colder than normal during the winter, and warmer during the summer. The physical environment was generally more favorable for parasite activity, and thus brought a slight increase in prevalence and intensity of the oyster diseases caused by Perkinsus marinus (Dermo) and Haplosporidium nelsoni (MSX). Among quarterly James River Survey sites, maximum annual P. marinus prevalences returned to levels typical of the mid- 1990s, before the years of drought. P. marinus prevalence reached 92% at Wreck Shoal, 56% at Point of Shoal, 68% at Horsehead Rock, and 8% at Deepwater Shoal, where P. marinus was observed for the first time since early 2003. More advanced, heavy infections became more numerous, but were limited to Wreck Shoal. H. nelsoni was restricted to Wreck Shoal, where it increased in maximum prevalence from 4% to 20%.



American Oyster Diseases, Virginia, Chesapeake Bay