Interacting effects of environment and cultivation method on biofouling of farmed oysters (Crassostrea virginica)

Abstract

Biofouling-induced increases in labor costs are among the most impactful factors determining the technoeconomic feasibility and profitability of aquaculture operations. Understanding how different cultivation methods and environmental conditions influence the severity of biofouling is crucial to support informed decision-making by farmers and minimize the economic impacts of biofouling in the aquaculture industry. This study used a factorial design to compare the extent and type of biofouling across three common cultivation methods (floating bags, floating cages, and bottom-culture) in exposed and sheltered locations that differ in temperature, salinity, turbidity, and wave energy. The ratio of fouling weight to oyster wet weight for oysters grown in floating bags was significantly higher than for oysters grown in floating cages, which were in turn significantly more fouled than bottom-planted oysters. Oysters cultivated in the exposed location had a significantly higher fouling ratio than oysters cultivated in the sheltered location. However, this pattern was driven by the stark difference in fouling by location for the floating bags, indicating that differences in temperature and wave exposure between sites would have the greatest impact on fouling severity for oysters grown in floating bags. Common fouling organisms included solitary and colonial tunicates, filamentous algae, and hard fouling (mussels, oyster spat, and barnacles). The significant differences observed in the composition and severity of oyster biofouling by gear type and growing site underscore the importance of considering fouling potential when evaluating the profitability of a farming strategy and the need for further development of region- and gear-specific biofouling mitigation strategies.