The eastern oyster (Crassostrea virginica) supports large markets throughout the eastern United States. In recent decades, wild stocks have observed major declines across the species’ range including in the Gulf of Mexico (Gulf). In 2019, the SALT consortium initiated a breeding program to support the developing industry in the Gulf with oysters bred for improved performance in different salinity environments. In September of 2020, the first generation was produced using 102 males and 102 females collected from 17 natural reefs between San Antonio Bay (Texas), and Cedar Key (Florida).
Families were bred according to a 2 x 2 factorial crossing design, pooled for common garden culture, and deployed at 7 growout sites in April 2021. At the end of the growout period, four sites were selected that represented high (AH) and low (MB, USM, LSU) salinity environments based on salinity conditions recorded during the growout period. The 204 founders and 6,414 offspring were assayed at 192 Single Nucleotide Polymorphism markers and the obtained genotypes were used to assign offspring to parent pairs using a likelihood ratio approach. Genetic parameters were estimated using animal mixed models in ASREML v.4.2. Estimates of heritability at low salinity ranged between 0.63 ± 0.06 and 0.84 ± 0.05 and were significantly higher than the estimate obtained at the high-salinity site (0.38 ± 0.08). Estimates of dominance variance did not differ significantly from zero. Genotype x environment correlations for growth rate ranged from 0.62 to 0.99 and were highest between low salinity sites (Table 2).