Development and Field Evaluation of a ROV-Based System for Moon Jellyfish Removal Operation

In recent years, the Seto Inland Sea has experienced extensive blooms of moon jellyfish ( Aurelia aurita ), resulting in substantial disruptions to the local fishing industry. Large aggregations of jellyfish clog fishing nets, damage gear, and reduce fish catches, causing significant economic losses for coastal communities. In 2023, unusually high jellyfish densities were recorded from April onward, and fishing operations in some areas were either severely curtailed or temporarily suspended due to the intensity of the blooms. Despite ongoing monitoring and localized mitigation efforts, no effective large-scale removal methods currently exist that can be rapidly and efficiently deployed under real marine conditions. To address this pressing issue, we developed a remotely operated vehicle (ROV) equipped with a custom-designed suction-and-shredding jellyfish removal device, capable of capturing and removing jellyfish in situ. The ROV was designed with a dry weight of less than 40 kg, enabling two operators to deploy and retrieve it without specialized lifting equipment. Field experiments conducted in the Seto Inland Sea demonstrated that, once a jellyfish was detected by the operator, removal typically required approximately 20 s. Additionally, the fragments collected after removal measured less than approximately 50 mm in diameter. According to previous studies on jellyfish regeneration, fragments of this size are incapable of regenerating. These field trials provided valuable insights into the ROV’s handling, effectiveness, and practical applicability. The results suggest that the proposed method has the potential to substantially reduce fishermen’s workload, mitigate economic losses, and contribute to sustainable marine resource management by providing a rapid and efficient response to large-scale jellyfish blooms.