高速曳網用超大目中層トロール網の模型実験

抄録

Midwater trawling technology has become important since the early 1980's for harvesting underutilized fast swimming fish. Developmental work has involved fishing trials with full scale midwater trawls by the Japan Marine Resources Development Center (JAMARC). Results of these trials have shown that some of the high speed midwater trawls with large meshes were effective in the capture of scattered shoals of pelagic species. The Japanese midwater trawls use meshes of up to 3m and these have beneficial effect of achieving higher towing speed and reducing net drag. However, insufficient data has been available to evaluate the effect of reducing net drag by the introduction of these large meshes.
Three models were used in this study to examine the differences in net drag at the range of higher towing speed; one being a standard model which was made after one of the JAMARC's designs and the others being control with smaller meshes in their body sections of the trawls. They are exactly the same in their design from wing to codend but differ only in use of large meshes in body sections. Results obtained indicate that a comparison between net drag and total twine area shows a good correlation for the three models, based on a method developed by Reid. The effect of large meshes on net drag can thus be evaluated from the correlation.