Louisiana contributes the majority of eastern oyster (Crassostrea virginica) landings in the United States, producing approximately 45% of average national oyster landings annually (NOAA Fisheries Landings, 2011-2021). Like other major fisheries, the eastern oyster fishery has seen major declines in recent years due to changing environmental conditions. As a sessile estuarine animal, oysters are subject to rapid environmental fluctuations, especially salinity, which can decrease rapidly in Louisiana’s estuaries due to storm events and freshwater diversions. Salinity in these estuaries often drops below the optimal growth and survival range for oysters (14-28; Lowe et al 2017). Louisiana has seen mass mortality events potentially due to extended periods of low salinity (<5) in the last several years, resulting in reduced C. virginica landings.
The Leveraging Opportunities and Strategic Partnerships to Advance Tolerant Oysters for Restoration (LO-SPAT) Project was launched in April 2021 with the goal of selectively breeding low salinity tolerant oysters to restore Louisiana populations in protected and fished reefs. To do this we are building genomic selection (GS) models for low salinity tolerance based on the results of a low salinity challenge (salinity 2, temperature 28°C) using oysters spawned from six Louisiana populations across three regions. Following the 45-day challenge, tissue from all live and dead oysters was sent out for genotyping on a custom C. virginica Axiom array (~66k SNPs). We will present the results of a genome wide association study along with the prediction accuracies of various GS models (Bayesian and GBLUP alphabets). Going forward, the best performing model will be used to select candidate broodstock for spawning based on genomic estimated breeding values and produce low salinity tolerant oysters to be planted at sites across Louisiana.