GROWTH AND MORTALITY OF DERMO-DISEASE-FREE JUVENILE OYSTERS (CRASSOSTREA VIRGINICA) AT THREE SALINITY REGIMES IN AN ENZOOTIC AREA OF CHESAPEAKE BAY

Abstract

Abstract Specific-pathogen-free (SPF) oysters (Crassostrea virginica) were set on shell and deployed on three oyster bars along a salinity gradient in the Patuxent River, MD, to determine growth, time to initial infection by Perkinsus marinus (causative agent for dermo disease), and subsequent mortalities. Initial deployment was in September 2000, during the second year of a 4-y drought. The salinity gradient experienced by these oysters during the drought was 4‰ to 6‰ above normal and provided ideal conditions for proliferation and dissemination of P. marinus. Oysters grew well during the first year, but mortalities rose rapidly during the second year, and reached 97% to 98% at all sites by the end of the second year. Although mean P. marinus body burdens reached levels of 2.3 × 107 cells·g−1 oyster tissue, MSX disease was also detected at both the lower and midriver sites in 2002, and was probably responsible for some mortalities at those sites. Due to extensive mortalities of the first deployment, we b...