Eastern oyster, Crassostrea virginica, populations have been declining steadily over the past several decades across the North American East coast. Great Bay Estuary (GBE), located in New Hampshire, is experiencing this loss and restoration efforts have been put into effect. This study characterized abundance in GBE from 2018 to 2020 of two early larval stages of C. virginica, D-hinge and veliger, and settled spat. The putative effects of month, year, site, and physicochemical factors were examined. D-hinge larvae and veligers already were present in the water column when sampling began (June), and spat settlement already had occurred, suggesting an earlier than previously thought first spawn of C. virginica in GBE. D-hinge larval abundances declined significantly from 2018 to 2020, whereas veliger abundances remained steady and increased slightly in 2020. Although physicochemical factors are known to play a role in larval abundance, no significant effects other than temperature were noted. Spat settlement was found as early as June, suggesting an earlier than previously thought spawning period of eastern oysters in GBE. The findings are being used to enhance restoration efforts as they suggest that spat brought in to augment current sites of active restoration should be collected and deployed earlier in the season and that recruitment devices should be deployed earlier each year.
