Abstract

The eastern oyster Crassostrea virginica is a major seafood species in the Eastern United States and is also highly valued for ecological services. The Gulf production is dominant accounting for over 50% of commercial harvests. Eastern oyster have been declining throughout most of their range due to habitat deterioration, overfishing, and outbreaks of Perkinsus marinus and other diseases. While this decline was initially mostly visible along the US East coast, it is now affecting the Gulf region where an estimated 50 to 89 percent of natural reefs have disappeared during the past 130 years (Beck et al., 2011). The restoration of natural oyster reefs to support exploitation by fisheries has been the focus of sustained efforts in recent years. In parallel, aquaculture programs have been developed along the U.S. east coast and in Gulf States including Louisiana, Florida, Alabama and, more recently, Mississippi. Efforts to improve production efficiency and disease resistance in the Gulf began at Louisiana State University with the development of a line resistant to P. marinus, selected from Louisiana native wild stocks (Casas et al., 2017), and tetraploid broodstock for direct triploid production (T. Rossi, personal communication). Triploid production aimed to achieve faster growth and mitigate disease mortality by reaching market size prior to the warm season prone to outbreaks. Mortality episodes continue to affect Gulf oysters (Casas et al., 2017, Wadsworth et al., 2019), despite of the increased use of triploid stocks for grow-out. These mortality episodes are still only incompletely understood but appear to occur primarily in late spring and early summer, the peak of the maturation and spawning season for eastern oyster, and to be related to extreme conditions associated with warm temperatures, variations in salinity, and possibly other stressors

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