Distribution of euphausiids in the Kuroshio front and warm water tongue with special reference to the surface aggregation of Euphausia pacifica

• Published in: Journal of Plankton Research
• Main Authors: Nishikawa, Jun, Tsuda, Atsushi, Ishigaki, Tetsuji, Terazaki, Makoto
• Format: Text
• Language: English
• Published: Oxford University Press 1995
• Subjects: ORIGINAL ARTICLES; Oyashio; Subarctic; Copepods
• Online Access: http://plankt.oxfordjournals.org/cgi/content/short/17/3/611; https://doi.org/10.1093/plankt/17.3.611

The distribution of euphausiids and other macrozooplankton was investigated in and around the Kuroshio front formed in the Ka.shima-nada Sea. Japan. during the summer of 1993. Zooplankton were dominated by copepods, chaetognaths and euphausiids. and their biomass was significantly higher at the frontal stations. Eighteen species belonging to six genera of euphausiids were collected. The species composition and community structure of euphausiids changed drastically with the ‘areas’ corresponding to the hydrological conditions. In the area under the influence of the Kuroshio. most euphausiids were warm-water species. In contrast. euphausiids found in the frontal area were those usually predominating in subarctic or cold Oyashio waters. In the area of the warm water tongue. where warm Kuroshio water lay above cold Oyashio water, the species composition of euphausiids represented a mixture of both warm- and cold-water species. Surface aggregations of Euphausia pacifica were observed in the frontal area during the night. The biomass and density of the aggregations ranged between 90 and 136 mg C m−3 and 164 and 238 md. m−3 respectively. These aggregations were mostly made up of immature individuals of < 12 mm. Passive transportation by convergent flow at the front seems to explain the observed surface aggregations of E.pacifica .