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

Marshall DA, Casas SM, Walton WC, Rikard FS, Palmer TA, Breaux N, La Peyre MK, Pollack JB, Kelly M, La Peyre JF. 2021. Divergence in salinity tolerance of northern Gulf of Mexico oysters under field and laboratory exposure. Conservation Physiology 9:10.1093/conjphys/coab065.


The eastern oyster, Crassostrea virginica, is a key foundation species within U.S. Gulf of Mexico (GoM) estuaries that has experienced substantial population declines. As changes from management and climate are expected to continue to impact estuarine salinity, understanding how local oyster populations might respond, and identifying populations with specific adaptations to more extreme changes in salinity will inform resource management, including restoration, and aquaculture programs. Wild oysters were therefore collected from four estuarine sites from Texas (Packery Channel = PC: 35.5 ± 5.1 annual mean salinity, Aransas Bay = AB: 23.0 ± 6.9) and Louisiana (Calcasieu Lake = CL: 16.2 ± 2.8, Vermilion Bay = VB: 7.4 ± 1.6) and spawned. The progeny were compared in field and laboratory studies under different salinity regimes. For the field study, oysters were deployed at low (6.4 ± 5.1) and moderate (16.5 ± 6.5) salinity sites in Alabama, USA. Growth and mortality were measured monthly. Condition index (CI), dermo infection intensity and shell height to weight ratio were measured quarterly. For the laboratory studies, oysters were exposed to salinities of 2.0, 4.0, 20.0 (or 22.0), 38.0 and 44.0 with and without acclimation and mortality recorded. The results of these field and laboratory studies with (acclimation) indicated that PC oysters are adapted to high salinity conditions, and do not tolerate very low salinities. The AB stock seemed to show the highest plasticity as it performed as well as the PC stock at the high salinities and as well as the Louisiana stocks at the lowest salinity. The Louisiana stocks did not perform as well as at the Texas stocks at high salinities. Different results were obtained with oysters with no salinity acclimation which likely reflects their ability to withstand extended valve closures rather than their adaptability of survival in different salinities.