東海黄海における基礎餌料の研究-I

Abstract

Plankton feature in the Yellow Sea and the center of the East China Sea in the winter of 1957 was discussed in comparison with that of preceding summer. The cold water from the Yellow Sea was powerful in the winter, jutting out farer southwards than in the previous summer. Of plankton, Calanus helgolandicus, its larvae, Euphausia pacifica, and Sagitta bedoti were as common as were in the summer, while Leptochela aculeocaudata which was abundant in the summer was not found at all in the winter in that cold water mass. On the other hand, an amphipod, Pontocrates altamariuns, was newly found to be abundant in the interior part of the Yellow Sea. Besides, the occurrence of many species of diatoms may indicate that it was at the earlier period of diatom flowering then9). The water from the Yantsu River remarkably jut out eastwards in consequence of the heavy rainfalls in the previous summer in the China Continent. Pseudoeuphausia latifrons and Labidocera euchaeta may be the indicator species there in the winter. The scarsity of phytoplankton may indicate the presence of discrepancy between the period of diatom flowering in this water and in the cold water mentioned above. The water under the heavy influence of the Kuroshio Current was powerless in this survey. Plankton were characterized by the abundance of species as well as in the summer. While the occurrence of a lot of colonies of Thalassiosira subtilus may be a token of the early period of diatom flowering then9).