Estimation of the Spawning Season of the Morid Fish Physiculus maximowiczi Collected from the Coastal Waters of Iwate Prefecture, Japan

Abstract

Physiculus maximowiczi is common in the coastal waters of Iwate Prefecture, northeastern Japan. A total of 1274 individuals were collected from the continental shelf at a depth of 50 m to 180 m from 1976 to 1980 and were examined for length frequency distribution, sex ratio and GSI. The mean body length of females was significantly larger (P<0.05) than that of males through the year. The mean body length increased in the summer and exceeded 300 mm and 270 mm in females and males, respectively. It decreased markedly in November. Females outnumbered males, and the total sex ratio was 19.4%. The ratio increased during the summer and decreased in November. The GSI increased from September to November and remained at a low level from December to August. But there were no mature ovaries during the year. Comparison of the GSI from two samples collected from 130 m and 330 m in depth during November and December, respectively, showed that the ovaries of fish from 330 m were more developed than those of fish from 130 m. The present results may suggest that P. maximowiczi spawns during the winter in deeper water than the continental shelf. © 1983, The Japanese Society of Fisheries Science. All rights reserved.