Analyses of fuel consumption, catches and usability of a modified trawl net constructed of ultra-high-molecular-weight polyethylene twine for pair trawl fishery in the East China Sea

摘要

Fishing experiments were carried out to reduce fuel consumption in pair trawl fishery in the East China Sea. A modified trawl was constructed with thinner twine of ultra-high-molecular-weight polyethylene (Dyneema) for the wings and the main body, except the belly. By using the modified trawl, fuel consumption during towing was significantly reduced compared to the conventional trawl constructed of thick polyethylene twine (p < 0.05, 8.5% reduction when the codend was open, 4.4% reduction when the codend was closed). Furthermore, CPUE of the total of commercially valuable species did not significantly differ (p > 0.05) between tows by the modified trawl (170.8 kg/h) and the conventional trawl (144.2 kg/h) as well as CPUEs of five commercially important species, such as yellow sea bream and Japanese butterfish (p > 0.05). However, on-deck labor increased by using the modified trawl because many fishes were entangled in the meshes of the main body. Thus, we confirmed that the modified trawl reduces fuel consumption while maintaining catch, but further modification is necessary to improve on-deck handling.