Seed production of the American Oyster, Crassostrea virginica, is a vital aspect of the off-bottom oyster culture industry. The availability of oyster larvae and seed has proven to be a limiting factor for farm grow-out operations in the Gulf of Mexico. A recirculating, artificial sea water hatchery could mitigate inconsistent larval and seed production experienced in flow-through hatcheries due to inconsistent and sub-optimal water quality parameters related to storm events, freshwater incursions, and other factors.
American Oysters were spawned at the University of Southern Mississippi’s Thad Cochran Marine Aquaculture Center’s recirculating, artificial seawater hatchery using temperature induction to produce diploid offspring. Larval performance was evaluated using percent hatch and percent survival to harvest. Percent hatch was calculated for each spawn attempt using the estimated total number of eggs fertilized and the estimated Day 2 larval counts. Percent survival to harvest was calculated using estimated Day 2 larval counts and harvested larval counts. All broods resulting in Day 2 larvae were used to calculate percent survival to harvest, including broods that had zero harvested pediveligers (PV). Throughout the 2018 to 2021 hatchery seasons, a total of 75 (26, 27, 11, and 11 per year, respectively) spawns were attempted resulting in annual harvests of 9.94 x 106, 74.70 x 106, 33.34 x 106, and 175.31 x 106 PVs for years 2018-2021, respectively. Improvements were achieved in the percent of broods making it to harvest, percent hatch, and percent survival to harvest. The percent of broods making it to harvest in 2018 was 11.5 to 90.9% in 2021. In 2018 and 2021, percent hatch improved from 40.26 to 43.36%, and the average percent survival to harvest by larval brood improved from 3.96 to 21.11%. Improvements in larval performance are attributed to system modifications, aging of ASW, and changes in the SOPs for larval culture. Major modifications and changes include the addition of a third filtration stage and increased filtration capacity removing greater amounts of nitrogenous waste and solids. Additionally, the inventory volume of artificial seawater was doubled from 2018 to 2021. The current average larval performance in TCMAC’s recirculating, artificial sea water system is comparable to averages in traditional, flow-through, natural sea water hatcheries.