Title:

Evaluation of Oyster Larval Abundance in the Great Bay Estuary

Larval abundances of the Eastern oyster, Crassostrea virgincia, have been steadily declining over the past several decades across the North American East coast. The Great Bay Estuary (GBE), located in New Hampshire, is experiencing this loss and restoration efforts have been put into effect. To optimize restoration efforts, this paper reports larval abundances of two early stages of C. virgincia, D-hinge and veliger, as well as settled spat, throughout GBE from 2018-2020. These larval abundances are compared based on date of sampling, year, site they were collected, and the physicochemical variables that were recorded on each sampling date. It was found that overall, D-Hinge larval abundances have declined significantly from 2018 to 2020 while veliger abundances have remained steady or increased. Although the physicochemical factors are known to play a role in larval abundance, very little significance was found, suggesting future study may need to be modified to include a broader range of factors (i.e., sampling for a longer range of dates). This study indicates that both D-Hinge, veliger, and spat settlement occur in GBE prior to when sampling traditionally has started (June), suggesting an earlier than previously thought first spawn of C. virgincia in GBE. This finding will allow restoration efforts to enhance their methods by deploying recruitment devices prior to the previously thought first spawn of each season. Further studies can focus on a variety of other factors (phytoplankton abundance, predators, etc.) for additional information on the decline in Easter oyster larval abundance in GBE.

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