On the Estimation of Sweep Area of Sweeping Trammel Net (Kogisasiami)

The sweep area of sweeping trammel net1) must be known in order to investigate its catch efficiency, which is defined as the ratio of the capture per unit operation to the living fish stock within the region swept by the operation.In the sweeping trammel net fishery, there have appeared no researches in this field, as far as the authors are aware.The present paper contains the discussions on sweep area of the sweeping tram mel net on the basis of the field experiment performed off Hamada, Shimane Prefec ture, during the summer of 1966.This experiment was undertaken to deduce an experimental relation to express the sweep area by the size of net, the duration of towing and the power of engine.Experimental Fishing gear: In the present experiment, two types, A and B, of trammel net were employed.The details of the type A are as follows.Inner webbing: twine; nylon 210 denier 3 strands, 0.04mm in diameter, mesh size; 60mm in stretched measure, 50 meshes in depth.Outer webbing: twine; nylon, 210 denier 6 strands, 0.06mm in diameter, mesh size, 360mm in stretched measure, 5 meshes in depth.