The Planktological Properties of the Principal Sea Areas Surrounding Japan

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概要

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• I. Oceanic groups. Kurosio and Oyasio are the important ocean currents, which affect the neritic region around Japan. Tusima current is, so to say, Kurosio and Liman current, Oyasio in the Japan Sea. They are characterized planktologically as follows:- (A) The Kurosio group is either Desmo- or Styli- or rarely Tripos-plankton. The diatom communities of.these plankton groups are nearly similar in composition to each other, and some forms such as mentioned just below are invariable components in them. Clima?odium biconcavum, C. Frauenfeldianum, Dactyliosolen tenuis, Ditylium sol, Gossreliella tropica, Guinardia flaccida, Hemiaulus Heibergii, H. hauck-ii, Leptocylindrus danicus, Planktoniella sol, G. Rhizosolenia, and Streptotheca indica. In addition to these diatoms, Amphorella, Epiplocylis, Proplectella, Rhabdonella, Tintinnus, and Xystonella of Tintinnodes are all good indicators of the Kurosio group. Radiates occupy usually more than 10%. (B) The Oyasio group. Animals are often larger in quantity than pants, and Copepods are the most prevalent. Of Tintinnodes, Parafavella, Cyttarocylis, and Ptychocylis are also the good indicators, Diatoms are usually most prominent, but sometimes peridinians become su-perior in number. Tripos- or Disco- or Thal'thric plankton are most often met with. Among diatoms, Coscinodiscus spp., Corethron hystrix, and Thal'thrix longissima are generaily abundant here. Bid. aurita, Detticula sp., Thal'sira Nordenskioldii, T. decipiens, and several forms of Subg. Phaeoceros are also the important forms in this group. (C) The Tusima current group has many species in common with the Kurosio group, although the neritic character is more or less distinctive here. In winter, this group is influe nced by the Liman group and the after-effects are also recognized even in spring. (D) The Liman group, the Oyasio group in the Japan Sea, possesses the species present also in the Oyasio group at least during winter. In summer, this group is usually influenced considerably by the Tusima current group and southern forms mingle with the northern ones here. (E) The Yellow Sea group is rather neritic in character and influenced distinctly by the Kurosio group. All these oceanic groups are uniform and stable both in composition and quantity through-out the vast area for considerable length of time. There is generally only a slight difference in composition between the summer and the winter plankton groups. II. The neritic group. The neritic group is characterized by the points:-(l) Plants are usual-ly larger in number than animals and occupy more than 80% of the total. (2) Animals are rich in kind, but Radiates and Copepods never attain to such high percentages as in the oceanic group. (3) Among diatoms, Chaetoceros is always the leading form. (4) In other cases, several diatoms form the simple floras either successively or abruptly. The simple flora is unique in the neritic region. The neritic group flactuates markedly in composition and in quantity, because the seasonal succession of diatoms and of other organisms takes place quick-ly, although the similar plankton association can last at least for two weeks or thereabouts.

• 社団法人 日本水産学会の論文

著者

• 相川 廣秋

  水産試験場

関連論文

• 魚類の年齢査定(豫報II)
• 魚類の年齢査定(豫報I)
• The Planktological Properties of the Principal Sea Areas Surrounding Japan

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