鮪延繩漁業における揚り繩について

抄録

Various conditions effected in tuna long-line operation were investigated on fishing boats belonging to Misaki port at Kanagawa Pref. (Table 1).
Some properties of tuna long-line already out of use were examined. (Table 2)
The results obtained are as follows:
1) The diameters of various tuna long-lines after use were found to have decreased by about 10 compared with untreated ones.
2) The force needed for bending a tuna long-line supported by two knife-edges were measured. (Fig. 1(A)) If the curvature and the span are constant, the relation of the force for bending, W, to the radii.s of line, γ, is empirically formulated as W=Kγ^3.2. For the change of curv-ature and the span of 1.0cm. and 10cm., respectively, value of K is given in Table 3.
3) The strengths of lines before and after use are nearly the same (Table 2). Durability against fatigue decreased with operations (Fig. 2). The disused lines were weak against fatigue compared with the unused (Table 4).