Design approach for a containment barrier system for in-situ setting of Crassostrea virginica for aquaculture and restoration applications

• A barrier structure was designed for the in-situ set of oyster larvae in a tidal tributary of Chesapeake Bay.
• CFD methods were used to estimate flow regime characteristics and drag coefficient values of the structure.
• System tension, shape and mooring configuration were specified with catenary equation approaches.
• During field deployment application, competent larvae were introduced onto emplaced cultch within the barrier yielding a spat set of approximately 180 juvenile oysters per m2.

As part of an applied research project, an engineering design and structure deployment study was conducted to investigate the feasibility of performing in-situ larval set of Crassostrea virginica within a temporarily deployed containment barrier. The intent of the barrier was to contain free-swimming larvae to maximize set on emplaced shell substrate. The project site was located in the Chesapeake Bay waters of Maryland (USA) in a tidal tributary adjacent to the Patuxent River. The project included a practical ocean engineering approach to specify barrier and mooring system components by investigating environmental design criteria, applying computational fluid dynamic techniques, and characterizing the barrier and mooring leg shape and tension with catenary equations. Following analysis and component specification, both the barrier and mooring system components were deployed. The structure consisted of two, 15 m length sections of Type-III turbidity curtain with a skirt depth of 4.57 m, but adjustable with furling lines. The structure enclosed an area of about 65 m2 with clean oyster shell substrate and was held vertical in the water column with ∼0.3 m floats at the surface and chain at the bottom of the skirt. It was deployed with an 8-point spread mooring configuration to maintain its shape in a 0.51 m/s current and 0.75 m waves. After deployment, larvae were introduced into the enclosed volume and allowed three days to set before removing the barrier. A companion biological field study demonstrated that the technique could add over 180 juvenile oysters/m2 to the site with clean cultch. Recommendations for a potential, scaled-up version are also discussed.