Dynamic Response and Safety-Constrained Configuration Optimization of an Oyster Longline Farm Under Extreme Waves

Korean oyster hanging longlines are flexible multibody mooring systems whose submerged weight increases as oysters grow. Current designs rely largely on field experience and static standards, which consider neither site-specific extreme waves nor the growth-induced sinking of droppers toward the seabed and each other. Whether standard configurations remain safe late in growth, and how to modify them, is unknown. This study analyzed the standard longline of the National Institute of Fisheries Science under a 50-year return-period design wave (Hs = 2.19 m, Tp = 8.85 s) from CMEMS data, using coupled time-domain simulations at oyster masses of 15, 20 and 25 kg per dropper. An elasticity analysis of five design variables (longline depth, dropper spacing, dropper length, and dropper and mooring stiffness) identified dropper length as the most influential. The reference design satisfied four safety constraints (seabed contact, dropper proximity, dropper swing and mooring load) up to 20 kg per dropper. A surrogate-based search with time-domain verification confirmed a design safe up to 20 kg at the reference productivity, whereas 25 kg per dropper required a relaxed proximity limit and 15% productivity loss. Configuration optimization must therefore be combined with on-site management such as buoy addition and harvest timing.