南太平洋の大型ビンナガの游泳層について-I : 試作たて繩によるビンナガの釣獲について

概要

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It has been presumed that the swimming level of albacore is generally deeper than that of other species. A study was undertaken to determine the swimming depths of the albacore by fishing by means of a newly designed vertical longline. The results are summarized as follows; 1) To equip with vinyl chloride triangular plates at the joints of branch lines were effective to prevent hook entanglements (Fig. 1). 2) Lesser influence of sea currents was seen upon the angle of inclination of the vertical longline. It was possible to sink the longline to 97% of the expected depth. 3) It was apparent that the opportunity of hooking albacore commenced with the settling period of the longline, as observed from an automatic depth-meter. 4) The rate of hooking was 4.7-5.4% at 200-300m depths, and 3.4% even at 380m depth. This fact suggests that the albacore swims in the deeper layers of the water.
公益社団法人日本水産学会の論文