Cooperative Fish and Wildlife Research Units Program: Louisiana
Education, Research and Technical Assistance for Managing Our Natural Resources

Despite nearly a century of exploitation and scientific study, our understanding of the combined effect of temperature and salinity on eastern oyster (Crassostrea virginica) mortality and growth remains regionally specific at best. In the northern Gulf of Mexico, for example, the complexities of these relationships are assumed from Atlantic estuaries where oysters generally experience cooler water temperatures and greater salinities. Using long-term (1988-2015) monitoring data from Louisiana’s public oyster reefs, we develop regionally specific models of temperature and salinity driven mortality (sack oysters only) and growth for spat (≤ 25 mm), seed (25-75 mm) and sack (> 75 mm) oyster size classes. Our results demonstrate that the optimal combination of temperature and salinity where Louisiana oysters experience reduced mortality and fast growth rates is skewed towards lower salinities and higher water temperatures. Outside of that optimal range, oysters are commonly exposed to combinations of temperature and salinity that are correlated with high mortality and reduced growth. How these combinations affect growth, and to a lesser degree mortality, appears to be size-class dependent. Given current climate predictions for the region and ongoing large-scale restoration activities in coastal Louisiana, our growth and mortality models are a critical step towards ensuring sustainable oyster reefs for long-term harvest and continued delivery of the ecological services in a changing environment.