The main function of work assistive suits is to reduce the burden on the muscles around the waist during stooping, thought to be the one of the causes of low back pain. Since fishermen frequently stoop, the introduction of work assistive suits is highly anticipated. In this study, the effect of a work assistive suit on the fish unloading task in a skipjack tuna pole and line fishing boat on offshore waters was experimentally investigated. A prototype work assistive suit, using carbon fiber-reinforced plastic plates as the elastic body of the suit, was manufactured and provided for the experiment. We measured the activity of the elector spine of four subjects using surface electromyography. The results showed that the muscle activities of the elector spine adjacent to the fourth lumbar vertebrate were significantly reduced in two subjects (the other two did not have successful experiments) and the rate of reduction ranged from 11% to 25%. The muscle activity in the elector spine adjacent to the first lumbar vertebrate was slightly increased in a subject, however, no significant changes were seen in other three subjects. It is expected that the work assistive suit considering actual work of fishermen is developed and disseminated.
The stock level of cone stripe shrimp Pandalus hypsinotus in Funka-Bay of Hokkaido has been estimated to be medium level in recent years; however, because most of the catch is occupied by small individuals, the protection of young shrimp is still an important issue. In this study, we investigated mesh selectivity for several stretched mesh size (32, 35, 39, 43, 46, 52, 65 mm) by water tank experiment. For each experiment, 15 bred shrimps were released into experimental area which installed two netting panels as partitions. The number of shrimps that passed or not passed (retention) the panel during night was recorded, and their carapace length was measured. The retention rate of shrimp in each mesh size decreased as the mesh size expanded: 0.99 (32 mm mesh size) to 0.37 (65 mm mesh size). From the master curve of mesh selectivity, the retention rate of 20 mm carapace length (recruitment size) was estimated as 0.71 at 32 mm mesh size used in the current commercial fishery. The mesh size at which 50% retention length (L50) is 20 mm was estimated to be 35.8 mm.
A series of burrowing experiments was conducted on a typical bivalve, Donax semigranosus, which lives in a sandy beach shoreline area, using sandy substrates of various particle sizes and shapes under standing conditions. As a result, the success rate of burrowing varied and decreased to below 30% when the particle diameter was over 0.8 mm and the vane shear resistance was less than 0.018 kN/m2 or greater than 0.14 kN/m2, or the friction coefficient tan Φ was less than 0.46 or greater than 0.88. This is thought to be due to the fact that the D. semigranosus cannot excavate the substrate with increasing hardness with a larger particle size over 0.8 mm under given dense packing states, and that the substrate is not strong enough to take the burrowing posture at low values of vane shear resistance and friction coefficient defined by tan Φ. In addition, it was considered that some individuals foot did not reach the substrate. These results suggest that the burrowing behavior of D. semigranosus is presumably adapted to sand dynamics in the shoreline area of the sandy shore, such as uprush and backrush, coastal gradients, and drifting sand.
Offshore wind power is capable of stable and efficient power generation and is expected to be a driving force for renewable energy. On the other hand, fishermen are concerned that the noise and vibration generated by offshore wind power will have an irreversible effect on wildlife behavior, especially habitats or migration routes of fish and shellfish, and fishing activities. In this paper, the following three items are summarized in relation to offshore wind power and environmental impact assessment. 1) the trends in the resent legal or public system and environmental impact assessment for the introduction of offshore wind power in Japan. 2) the basic concept of evaluation items when conducting an environmental impact assessment on offshore wind power. 3) the recommendations for the construction of fishery-cooperative offshore wind power that dispels the concerns of fishermen.