| Popis: |
To obtain some fundamental suggestions on the gear efficiency of the three different types of trawl net, the authors carried out the model experiment, and compared them with each other, basing on the physical characteristics of the net. Thefirst is the two-seam-net was used in 1950's in East China Sea; the second is thefour-seam-net was used in 1960's in Bering Sea; the third is the six-seam-net wasused on board of the "Nansei Maru". These three nets aimed for catching the demersal fishes. The results obtained in this study are summarized as follows:(1) The towing speed, when the height of net mouth is stable, differs in eachnet. The towing speed is about 2.3 knot on the two-seam-net, about 2.6 knot on thefour-seam-net and about 3.0 knot on the six-seam-net. On ordinary towing condition, the height of net mouth on the four-seam-net is the highest, marking about6.0-9.0 percent of the maximum breadth of the net, among the three types of trawlnet.(2) Net resistance is explained by general equation R=k V^, and the values (n),the highest values observable in the four-seam-net, marking 1.64-1.99, the secondis the values of two-seam-net, marking 1.42-1.64, and the third is those of six-seam-net,marking 1.32-1.53. |
