A small structure made of rigid plastic mesh (W1.2×D1.2×H0.8 m) was attached to the mooring gear to provide habitat for marine organisms. The occurrence of fish and cephalopods around the mooring gear with a small structure and around the normal mooring gear were compared by a time-lapse camera observation and an environmental DNA analysis. The experiment was conducted in Tachibana Bay, Nagasaki Prefecture, at a water depth of approximately 20 m over an 8-month period from November 2021 to July 2022. The time-lapse camera recordings observed 17 species of fish and bluefin reef squid Sepioteuthis lessoniana, while the environmental DNA analysis identified 49 species and 3 genera of fishes other than those observed by the time-lapse camera. The similarity of the fish fauna was more influenced by differences in survey methods (time-lapse camera and environmental DNA) than by differences between the mooring gear with a small structure and the normal mooring gear for the same time period. The maximum number of individuals of certain species observed together at any one frame in 24 hours (MaxN), which is an estimator of relative abundance, was calculated. MaxN for thread-sail filefish Stephanolepis cirrhifer, red seabream Pagrus major, jack mackerel Trachurus japonicus and bluefin reef squid was significantly higher in the mooring gear with the small structure throughout the observation period (p<0.05). Mooring gear with a small structure can be used to provide a habitat for certain marine organisms.

This study examined the effectiveness of work improvement activities as a methodology for enhancing safety in fisheries. A survey was conducted in set-net fisheries operated by the Noda village fisheries cooperative association (Below, FCA), Hirono town FCA, Kuji city FCA, and Ogonaihama FCA. In each region, workshops were held in 2014 and 2015 to show the procedures for implementing voluntary improvement activities. The survey evaluated the status of the following activities conducted by each FCA since 2016: implementation of work improvement activities, continuation of safety training sessions for fishermen, and whether any new activities other than those implemented in the initial training sessions were started. The results showed that work improvement activities continued in all FCAs. Regarding the continuation of safety training, in some areas, social workers and other instructors have been continuously employed as lecturers, whereas in others, meetings (instead of workshops) have been held for fishermen to raise safety awareness. In addition, two newly implemented improvement activities were identified, i.e., manualization of standardized work and sharing among fishermen. Thus, it was confirmed that these voluntary activities have been effective since their implementation because the “methodology” adopted to achieve improvement was presented rather than specific improvement points.

For fishermen engaged in aquaculture and set-net fishing, it is extremely important to know and maintain the condition of underwater nets. These nets face the risk of breaking due to fish and marine animals biting at them or the impact of strong currents. Additionally, since the nets are fixed underwater for extended periods, they are prone to accumulation of shellfish, algae, and parasite eggs. In aquaculture, this can lead to oxygen deficiency for the fish. In set-net fishing, the nets become heavier when hauled, reducing work efficiency. To address this, the author developed an underwater robot that crawls along the net to monitor and maintain it. This robot is composed of two units, each equipped with magnetized wheels that allow it to grip the net from both sides and move along it using magnetic force. By equipping this robot with a camera and cleaning device, it becomes possible to monitor and maintain the net’s condition. However, when testing a small prototype of the robot on a net, it was unable to overcome the net’s uneven surfaces due to its small wheels. Consequently, a larger robot with thicker wheels was developed and tested to see if it could overcome obstacles. Additionally, as the larger robot is more susceptible to the effects of water currents, CFD (Computational Fluid Dynamics) analysis was conducted.