Evaluating Farmed Atlantic Surfclam (Spisula solidissima) Grow-Out Performance across Three New Jersey Bays

The Atlantic surfclam (Spisula solidissima) is emerging as an important species that is helping to diversify the aquaculture sector of the Northeast United States. Over the last few decades, farming techniques for the species have been investigated; however, critical knowledge gaps remain in the surfclam husbandry literature. In particular, few studies have examined the grow-out phase of surfclam aquaculture production in back bay environments, which has impeded the widespread adoption of commercial surfclam aquaculture. To address this gap, experimental grow-out trials were conducted at multiple locations in New Jersey. Farmed surfclams were deployed at three commercial shellfish farms situated in high-salinity back bays and the growth, survival, condition, sex ratio, and gonad maturation of the clams were monitored. Sediment composition, temperature, salinity, dissolved oxygen, turbidity, and chlorophyll a concentration were recorded throughout the trials to provide additional information about how environmental conditions may influence farmed surfclam performance. At deployment, the mean shell length of the surfclam seed ranged from 12.87 to 16.74 mm. Generally, surfclam growth rates were consistent across farms, but varied seasonally. Within 9 months, 67%–98% of clams reached market size (31.75–44.45 mm). Surfclam condition also varied seasonally, peaking in the spring and falling to low values in the summer and fall. Survival varied considerably across farms and deployment years, ranging from 0% to 77% after 9 months. Surfclam mortality was associated with warm temperatures, predation, anoxic conditions from siltation, and aerial exposure during a harsh winter. Although this study demonstrates that surfclam aquaculture is feasible in coastal New Jersey bays, additional research is required to reduce surfclam mortality in shallow estuarine bays, particularly during warm summer months.