Studies on the Fishing Gear and the Fishing Efficiency of the Two-Boat Trawl Fishery (Preliminary Report) : Some Problems on Construction of the Net Made of Manila Twine

Two-boat trawl nets used in the Eastern China Sea and in the Yellow Sea can be divided into two classes from their constructions and efficiencies; in this paper, one is conveniently designated as the "northern type", and the other the "southern type". Comparative studies were made on their constructions and shapes under water in relation to their fishing efficiencies. The results obtained are as follows: (a) The entrance of the northern type net under operation was postulated to be larger in height than that of the southern type. The northern type net was more effective for the catch of Pseudosciaena manchurica (JORDAN et THOMPSON) and Miichthys imbricatus (MATSUBARA) than the southern type, while the southern type net gave a more efficient catch for Argyrosomus argentatus (HOUTTUYN) and Taius tumifrons (TEMMINCK et SCHLEGEL). (b) It was confirmed that the increase in the height of the entrance was followed by the increase in the catch. However, it is very probable that the shape of the net as a whole rather than the shape of the entrance induces, under certain circumstances, a more pronounced effect on the fishing efficiencies