Ecological distribution of eggs of common sea bass, lateolabrax japonicus (cuvier) in Tokyo bay

Abstract

Common sea bass, Lateolabrax japonicus (CUVIER), is one of the commercially important fish taken from Tokyo Bay. The present paper deals with such ecological aspects of this species as seasonal and geographical distributions of eggs. (1) The materials were taken through the cooperative investigation of neritic-pelagic resources carried out by the Kanagawa Prefectural Experimental Fisheries Station and Tokai Regional Fisheries Research Laboratory during the years 1955-1962. They were collected by vertical haul of the plankton net with 45cm- or 60cm-mouth-diameter from a depth of 150m (or ocean bottom when shallower) to the sea surface. (2) The eggs occur in the season from the late October till the late February with its peak at the late November through the late January. The eggs were collected chiefly from the entrance of Tokyo Bay and partly from inside of the Bay (close to the entrance) and from Sagami Bay. None of eggs were taken from the innermost region of Tokyo Bay, The density of the distribution represents some variation year by year, but no remarkable differences are observed in pattern. (3) The eggs most frequently occur within 14 ~ 20°C in temperature and 18.0~19.2% in chlorinity, i. e. in the coastal waters under a considerable influence of open sea water. The frequency is very low within the bay where temperature is lower than 13°C in winter and chlorinity Is usually lower than 18%. (4) Larvae penetrates into Tokyo Bay after hatched out. The grown fish become to the spawners in November migrating from the inner region of the bay to the entrance of the same. © 1965, The Japanese Society of Fisheries Science. All rights reserved.