豊後水道におけるcopepodaのnauplius期幼生の分布密度とカタクチイワシの卵・稚仔出現量の季節的変動

抄録

Copepod nauplii are the most important plankton among food resources for the larvae of clureidae. Many ichthyologists assured of this fact from investigations on stomach contents of the larvae. The present paper reports the result of a study on the distribution of copepod nauplii and the occurrence of eggs and larvae of Engraulis japonica in Bungo Channel. The survey was carried out in the period from April 1963 to March 1964 at the six stations shown in Fig. 1. The results obtained were summarized as follows.
(1) There were two high reproductive seasons of copepods in one year. One of them was centering around June and another around October. The former was especially eminent at the southern water, starting at the earlier time such as May. The latter was eminent at the nothern water, and less reproductive activity was observed in the southern area.
(2) The main spawning seasons of Engraulis japonica are found to be in May and Sep-tember. But in September, the occurrence of the egg and larvae were not so eminent as in May, and the spawning ground was in the southern area of Bungo Channel.
(3) A difinite correlation between the seasonal change of the total number of copepod nauplii and the emergence number of eggs and larvae of Engraulis japonica was clearly obseved in the southern area of Bungo Channel.