分離漁獲装置付き2階式小型底曳網の分離効果 Preliminary Trawling Tests using a Two-level Beam Trawl with Square Mesh Separator and its Separation Efficiency
A two-level beam trawl was developed with a square-mesh separator panel in it to separate marketable fish and shrimp from non-commercial crabs and smaller fish. The net-mouth of the lower cod-end in the two-level trawl gear was covered with a square-mesh net panel as a separator. Fishing experiments of the gear were conducted with a chartered trawler off Shimonoseki city in October 1995. Two square-mesh net panels of 40 and 50mm mesh bars were used in the fishing experiments. The net mouth openings of the upper and lower cod-end associated with the efficiency of the separator were measured. The total number of animals caught in 7 hauls was nearly 2, 300. Separation efficiencies defined as the ratio of the catch in the upper cod-end to the total catch of 11 species were compared by two mesh bar sizes. Non-commercial crabs passed through the separator panel and then entered in the lower one, while shrimp were caught in the upper cod-end although its body was enough small to pass through the separator. Separation efficiencies of the main 6 species plotted versus bodysize indicate that the separator has size-selectivity to some extent. Thus, the gear was useful to catch fish of marketable size and shrimp in the upper cod-end.
日本水産学会誌 64(2), 189-196, 1998-03-15