Fishing Centre of “Sanma” Cololabis saira (Brevoort), correlated with the Head of Oyasiwo Cold Current

Abstract

From the records of five years from 1931 to 1935, the writer can follow two loci of the fishing centre of “Sanma”, corresponding to the two branches of Oyasiwo Cold Current (Figs. 1 and 2).
Of the two loci, the coastal one appears from October, while the off-shore one from Sep-tember. In autumn the fishing centre lies at the southernmost head of cold current, usually in the zone of temperature of 16 to 18°C, or is located slightly to the east of it, which is supposed to form a convergent cyclonic vortex. The shoals of “Sanma” migrate in the direction of maximum gradient of surface temperature or that of axial line of the elliptic curves representing equally dense catches. According to the fluctuation of the intensity of two branches of cold current, the fishing at each of two centres relatively grows or decays. Coming down to the region off Kinkwazan, the off-shore fishing centre stays there for a comparatively long period, decaying gradually, while the coastal centre is, to the contrary, gradually animated.