Studies on development of a multiple opening/closing frame trawl for sampling larval and juvenile fish

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In this research, the new multi-sampling trawl with automatic net opening and closing control system was developed to sample pelagic juvenile fish. A net-release controller is used, which not only controls the net release mechanism but alsorecords the net depth, temperature and flow rate during net towing.The field experiment was carried out using training ship Shinyo-maru, and RV Kaiyo-maru in Sagami Bay. From the results, the net maintained almost constant depth under towing speed from 2. 0-4. 0kt, and the nets were surely opened/closed smoothly by the command from the controller. The newly developed multi-sampling trawl is considered to be suitable for quantitative layer sampling of juvenile fish.