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

Authors: KRASNOW, RUBY - University Of Maine; KIFFNEY, THOMAS - University Of Maine; CUDDY, ROBERT - University Of Maine; BRADY, DAMIAN - University Of Maine

Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2025
Publication Date: 5/12/2025
Citation: Krasnow, R., Kiffney, T., Cuddy, R., Brady, D.C. 2025. Interacting effects of environment and cultivation method on biofouling of farmed oysters (Crassostrea virginica). Journal of the World Aquaculture Society. 56(3). Article e70012. https://doi.org/10.1111/jwas.70012.
DOI: https://doi.org/10.1111/jwas.70012

Interpretive Summary: Over 95% of all oyster production in the United States currently comes from aquaculture, and the shellfish aquaculture industry in the Northeast continues to expand to meet growing consumer demand. Suspended culture is the predominant oyster cultivation method in many regions of the world, although many farmers utilize bottom planting (in which oysters are grown directly on the sea floor without being contained in any sort of cage, bag, or basket). Among suspended culture methods used in New England, the predominant geartypes are floating mesh bags and pontoon-supported wire cages that hold multiple meshbags, although grow-out tumbler systems (e.g., ZAPCO™, SEAPA™) have also been adopted by some growers.

Technical 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.