著者

山口 篤

出版者

Faculty of Fisheries Sciences, Hokkaido University

雑誌

Memoirs of the Faculty of Fisheries Sciences, Hokkaido University (ISSN:21861927)

巻号頁・発行日

vol.53, no.2, pp.13-18, 2011-06

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Recent advances in studies on zooplankton ecology in the Oyashio region were reviewed. In this review, the following three topics were argued : i) ecosystem structure in the region, ii) inter-annual changes in zooplankton biomass and iii) optical analysis on zooplankton samples. Annual mean biomass in the Oyashio region was estimated to be 23 g C m-2 and was dominated by mesozooplankton (34%), followed by phytoplankton (28%), heterotrophic bacteria (15%) and microzooplankton (14%). Within the mesozooplankton, large grazing copepods (i.e. Neocalanus spp., Eucalanus bungii and Metridia spp.) were the most important taxa to govern the seasonal and inter-annual variability. Through the analysis on zooplankton samples collected during 1950’s to present, inter-annual variability in mesozooplankton biomass was revealed to be related with the Pacific Decadal Oscillation (PDO) and climate regime shift. While the zooplankton size is important to determine the food quality for pelagic fishes and the mass flux to the deep ocean, detailed analysis on their size distribution is not made for most of the samples, because of the difficult and time consuming analysis involved. The recently advanced optical plankton counter (OPC) can measure the particle (=plankton) with detailed size distribution (4096 size unit between 0.25 mm and 20 mm) within a short period, therefore the application of OPC on zooplankton samples may solve the problem in future.

著者

Tatsuta Naoki Imamura Hisashi Nakaya Kazuhiro Kawai Toshio Abe Takuzou Sakaoka Keiichiro Takagi Shogo Yabe Mamoru

雑誌

Memoirs of the Faculty of Fisheries Sciences, Hokkaido University (ISSN:21861927)

巻号頁・発行日

vol.56, no.1, pp.1-64, 2014-05

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A taxonomic examination of 3,108 specimens of mesopelagic fishes, collected around the Ogasawara Islands in December 2010 by a beam trawl net operated from the T/S Oshoro-maru, Hokkaido University, Japan, resulted in the recognition of 99 species representing 34 families and 65 genera. Descriptions are provided for all species, two of them〔 a stomiid Eustomias braueri Zugmayer, 1911 and linophrynid Haplophryne mollis (Brauer, 1902)〕 being new records for Japan. Three species, a stomiid Eustomias sp., trachipterid Desmodema sp. and oneirodid Oneirodes sp., could not be identified at the species level