Growth and management of the intertidal smooth Venus clam Chionista fluctifraga under different aquaculture strategies

The intertidal Venus clam Chionista fluctifraga is an important food resource in northwestern Mexico, but in some places, natural populations have been overexploited or driven to depletion. Aquaculture appears as an alternative for sustainable production of emerging species. Therefore, the objective of this study was to apply several strategies for the production of C. fluctifraga with spat produced in the hatchery, including off-bottom culture and bottom culture (without protection, partial protection and total protection). The performance in culture of spat produced during two different years was also compared. Likewise, multi-model inference was used to determine the growth models that best fit each type of culture. Off-bottom cultivation for two years was successful in obtaining commercial size clams (31.0 & PLUSMN; 4.8 mm shell length and 11.1 & PLUSMN; 5.1 g total mass) and a survival of 60%. Bottom culture suffered intense predation in all cases (100% mortality), but it was possible to produce clams of commercial size (33.8 & PLUSMN; 3.7 mm shell length and 12.0 & PLUSMN; 3.6 g of total mass) after 8 months in the culture with total protection. Better performance was found for the spat cultivated during 2017-2018 compared to the one cultivated during 2016-2017. The differences were associated with variances of environmental variables between years. The best fits to the growth data in the diverse scenarios were found in different models; Gompertz for off-bottom cultivation for two years and for the combination of off-bottom and bottom cultivation, Asymptotic regression for off-bottom cultivation for one year, and Beta for bottom cultivation only. Despite predation mortality, our study offers two ways to produce commercial-sized clams, using off-bottom cultivation for two years and combining pre-growth in off-bottom cultivation and growth-out in bottom cultivation. Hatchery spat is sensitive to environmental variation but showed satisfactory performance in both years. Growth models selected for each culture scenario could help determine various aspects of clam growth and make production projections.