Hydrodynamic Optimization of Adjustable Scallop Dredge Systems With Negative-Angle-Arc Plates for Sustainable Benthic Trawling

Abstract

Scallops are highly prized shellfish in the North Yellow Sea and are primarily harvested using trawling methods. However, this harvesting method has resulted in the incidental bycatch of other benthic organisms, negatively impacting the seafloor ecology, and ultimately hindering the sustainable development of the scallop industry. To mitigate these issues, modifications were proposed, including an adjustable hydraulic plate, flexible connections, and elastic components to reduce damage, sediment content, and bycatch. Key causes, including net gear leakage, rigid teeth injuries, and sediment disturbance, were identified through underwater monitoring and hydrodynamic analysis. Simulations of various hydraulic plate designs have revealed optimal parameters for minimizing drag resistance and maximizing efficiency, with the negative-angle-arc plate demonstrating superior performance under specific conditions. Optimal trawling parameters, including rope lengths, drag forces, and angles, were established for towing speeds ranging from 1.5 to 2 m/s at depths of 30–50 m. Setting the net opening at 350 mm, below the rising current height of the hydraulic plate, was found to effectively increase scallop harvests, while reducing bycatch of benthic fish. These findings provide actionable insights for sustainable scallop trawling practices.