The decline of natural reefs of the eastern oyster (Crassostrea virginica) in the northern Gulf of Mexico (Gulf) has stimulated the development of aquaculture to support the market demand and restoration programs. Gulf habitats feature diverse salinity environments that may require oysters bred for habitat-specific optimal genetic characteristics. Here, we report the performance of eastern oyster bred in low-salinity environments after one generation of selection.
Selective breeding employed a common-garden approach where families were pooled at fertilization for communal rearing and molecular pedigrees were used a posteriori to determine parentage and estimate breeding values in a walk-back selection process. The F1 generation pool was bred in 2020 and included 202 full and half-sib families that were deployed on three low salinity sites and two high salinity sites for growth challenge. Breeding values (BV) for height were estimated at harvest size in fall 2021.
Parents with highest BVs were bred in 2022 with a selection differential of 5.4% within low salinity and a selection differential of 2.61% from two high salinity sites. A control pool was also generated using 25 full sib families with BV’s deviating -0.086% from the high select and +0.15% from the low select.
Offspring were deployed at 6 growout testing sites in fall of 2022, 4 low salinity sites received oysters selected for performance at low salinity and 2 high salinity sites received oysters bred for performance at high salinity. Selected oysters at two low salinity test sites had significantly greater survival at peak mortality (Fig. 1) and shell height 10-months post deployment than control oysters, indicating positive response on growth and correlated increase in survival. There were no significant differences in growth between the selected and control oysters at high salinities sites, potentially reflecting the lower selection differential within the high salinity line