COMPARISON OF DIPLOID AND TRIPLOID EASTERN OYSTERS Crassostrea virginica IN FLOATING GEAR IN GEORGIA

With the growth of oyster aquaculture in the US there has been an increased interest to launch oyster aquaculture in Georgia as a way diversify the oyster industry that is dependent upon bulk harvest of wild oysters.  Current shellfish leases in Georgia cannot utilize gear, but as the industry looks to grow there is much interest in floating gear and to examine the effect that ploidy has on the growth, survival, and condition of oysters.

Research from other states in the southeast have found benefits to utilizing triploid oysters for aquaculture and therefore, for this study we tested the effect of ploidy on growth, survival, and condition of oysters in floating cages (OysterGro) at an experimental site adjacent to a commercial shellfish lease in Wassaw sound. Four cages of each ploidy (3,600 oysters) were set out in six bag floating cages at density of 150/bag in October 2017. Cages were flipped once a week for 24 hours and growth was measured quarterly from ten oysters per bag through September 2018. In June 2018, prior to summer, and September 2018, post summer, ten oysters were removed and frozen to assess the condition and amount of fouling. Diploid oysters used were spawned in the Shellfish Research Laboratory hatchery, from Georgia broodstock, and triploid oysters were spawned at Lady's Island Oyster Co. hatchery from South Carolina broodstock, in early May 2017.

At deployment diploids had a mean shell height of 27.4mm and triploid had a shell height of 30.9mm.  By December 2017 diploid and triploid oysters had increased in size to 38.2mm and 40.2mm and by March 2018 sizes were 41.5mm and 44.0mm, respectively.  In June, ten live oysters were collected and frozen from each bag for measurement, fouling and condition index.  Remaining oysters were left in place and harvested in September 2018 and ten removed from each bag for measurements and to determine the amount of fouling and condition index.

Results from this research furthers the research comparing the effect of ploidy on the growth of oysters, provide information to the state of Georgia on the effectiveness of floating gear, and give potential oyster growers needed information as they look to invest into oyster aquaculture once regulations are adopted.