Location: National Cold Water Marine Aquaculture Center
Project Number: 8030-10600-001-073-A
Project Type: Cooperative Agreement
Start Date: Jul 1, 2025
End Date: Jun 30, 2030
Objective:
To establish a genetic improvement program for eastern oyster aquaculture in the Gulf of America by developing a genetically diverse, high-performing, salinity-tolerant tetraploid line.
Approach:
In the Gulf of America (GoA), oyster farmers prefer to rear triploid oysters because they grow faster and divert less energy to reproduction such that meat plumpness is maintained throughout the year and a more consistent product is delivered to market. The standard practice for generating triploid oysters is by mating tetraploid males with diploid females, but creating tetraploid lines is a complex process that requires several generations of breeding. Oysters in the GoA also experience fluctuations in salinity due to river discharge, heavy rainfall, and drought events. Extremely high and low salinities introduce stress, which negatively affects oyster growth, survival, and reproduction. Previous research suggests that GoA eastern oyster populations vary in their response to salinity stress and that this variation can be exploited to select for salinity tolerance. Here we will develop new GoA tetraploid lines from low and high salinity tolerant stocks in order to produce salinity tolerant triploids for the GoA oyster aquaculture industry.
Oysters will be spawned and reared according to in-house protocols developed the Cooperator. In year 1, salinity tolerant male and female diploid oysters will be spawned and extrusion of the second polar body during meiosis will be chemically arrested in fertilized embryos to induce triploidy. Triploid seed oysters will be grown to maturity. In year 2, triploid oysters will be shucked, sexed, and inspected for ripe gonads. Ripe triploid females will be strip spawned and crossed with salinity tolerant diploid males. Meiosis will be chemically arrested prior to extrusion of the first polar body to create tetraploids. Tetraploids will be raised to maturity and in year 3, they will be crossed to one another to create a large population of salinity tolerant mated tetraploids. Subsequently, diploid females will be crossed with tetraploid males to create selected triploids.
Field and laboratory trials will be conducted to compare performance of selected and unselected stocks. For the field studies, three oyster lines (3N selected, 3N half-selected, and 3N non-selected) will be evaluated at three farm sites with distinct salinity profiles. Four replicate bags of each line will be deployed at each site for 12 months. Survival and morphometric data will be collected monthly and differences in mortality and growth rates among lines will be analyzed using factorial repeated measures ANOVA models. Laboratory experiments will focus on scope for growth to assess the effects of stress on triploid performance and the effects of genetic background on the response to stress. Two temperatures and three salinities will be included as experimental treatments. In addition, laboratory experiments looking at differences in gamete production and quality among selected and unselected diploid and tetraploid lines will be conducted.