Abstract
The catch of Trachurus japonicus (T. & S.) in the North-Eastern Sea Region of Japan was investigated with specially related to the optimum ranges of water temperature and salinity for catch, based on the hydrographical observations made at the same time and place of the set-net at Enoshima, Miyagi Prefecture, for the period from 1936 to 1947.
(1) It was suggested that this jack-mackerel distribute in snmmer over the North Eastern Sea Region of Japan swimming mainly with the front of Kuroshio current, within the range of temperature from 18.0 to 24.0°C and salinity from 32.80 to 33.70 S‰ at the surface.
(2) Near the northern boundary (presumably Iwate Prefecture) of the distribution, the yearly catch were effected mainly by the hydrographical conditions.
(3) The main parts of the catch at Sendai Bay in July, 1949, were composed of the three-ring fishes of body length from 23.0 to 24.8cm. and zero-ring fishes of body length under 8cm.
