Evaluation of a novel design of floating net cage with hybrid side and bottom nets in current

The floating cage system is the dominant technology used for marine aquaculture. While traditional HDPE cages with fiber nets have been extensively studied, it is important to highlight that research on the performance of floating cages equipped with metal nets, as well as those with hybrid metal-fiber nets, remains relatively limited. Based on flume experiments, we mainly investigated the net deformation and drag force of the square and octagonal cages featured with hybrid side and bottom nets in currents, together with the effect of bottom weight. The results indicate that increasing bottom weight effectively reduced cage deformation at lower flow velocities but became less effective at higher velocities, where the influence of flow velocity on drag was more significant. The use of a metal bottom net had a limited impact on cage performance, primarily due to the alignment of the bottom frame parallel to the water flow. Both HN-FN (hybrid fiber-wire and fiber net) and WN-FN (wire and fiber net) cages retain a similar volume of over 60 % at high flow velocities. However, the drag on WN-FN cages is significantly higher than that on HN-FN cages, indicating that the HN-FN configuration offers a more advantageous balance between structural stability and reduced drag under high flow conditions. Octagonal cages consistently outperform square cages at both lower and higher flow velocities, particularly excelling at higher velocities. However, square cages offer distinct advantages, such as simpler construction, easier maintenance, and improved water exchange. Moreover, the bottom frame and vertical wire ropes effectively regulate cage deformation and preserve structural integrity. These findings can provide valuable guidelines and recommendations for optimizing net system design to enhance performance under diverse flow conditions.