UNDERSTANDING THE EFFECTS OF STOCKING DENSITY AND BIOFOULING CONTROL PRACTICES ON BIOFOULING ON OFF-BOTTOM OYSTER GROW-OUT BAGS (YORK RIVER, VA)

Abstract

Virginia, the top producer of Crassostrea virginica (Eastern Oyster) in the United States, supports a fast-growing commercial shellfish aquaculture industry valued at over $30 million. Biofouling is the adhesion of aquatic communities to submerged structures that can have ecologic, biologic, and economic impacts on aquaculture operations. Colonized bags have increased weights that affect handling and blockages that can impede essential water flow, which could affect conditions within grow-out bags. Biofouling contributes to 5-10% of production costs and 20% of the direct costs of an oyster's final market price. This study aimed to (1) quantify and identify fouling communities on floating oyster bags and (2) determine the effects of biofouling control practices (air drying periodically vs not) and stocking density (high, normal, and empty) on biofouling communities growing on mesh settlement plates attached to floating oyster bags. Results indicate that colonizing organisms (Tubeworm fouling and bryozoans) were the most prominent taxa found across most settlement mesh plates. Air drying frequently effectively reduced biofouling, producing significantly lighter wet weights on both mesh plates and grow-out bags than non-air-dried treatments (p < 0.01). Stocking density somewhat reduced biofouling in non-air-dried treatments, albeit not significantly. Understanding which biofouling communities grow on oyster bags and developing mechanisms to control fouling growth can help researchers provide better data for oyster farmers so they can make more informed husbandry decisions.