Bulletin of the Plankton Society of Japan
Online ISSN : 2434-0839
Print ISSN : 0387-8961
Volume 69, Issue 2
Displaying 1-22 of 22 articles from this issue
Original Papers
  • Akiko Michiyama, Akihiko Fujii, Kyohei Yamada, Tomoki Umeda, Junji Tak ...
    2022 Volume 69 Issue 2 Pages 83-92
    Published: August 25, 2022
    Released on J-STAGE: September 17, 2022

    In Ariake Bay, catches of the manila clam Ruditapes philippinarum have decreased considerably due to the low rate of larval return to adult habitats, shrinkage of larval networks among each local population, and shortening of the occurrence period of larvae. In this study, we examined the seasonal and annual occurrence trends of planktonic clam larvae and the environmental factors related to the quantity of larvae based on surveys conducted in the Ariake Sea between 2015 and 2018. In the Ariake Sea, emergence peaks with population densities of more than 1,000 m−3 individuals occurred during the spring and fall spawning seasons. In spring, the peak onset often occurred between late April and May, but trends also varied from year to year. In autumn, the peak period was observed at approximately the same time every year, from mid-October to November. The peak emergence of plankton larvae was thought to be related to water temperature.

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  • Yusuke Manako, Toru Kobari, Mutsuo Ichinomiya, Tomohiro Komorita, Akim ...
    2022 Volume 69 Issue 2 Pages 93-101
    Published: August 25, 2022
    Released on J-STAGE: September 17, 2022

    It has been thought that food availability for fish larvae was poor in the Kuroshio because of the low standing stocks of plankton in the oligotrophic conditions under thermal stratification throughout the year. Despite a potential risk or disadvantage for larval survival and growth, Kuroshio and its neighbouring waters are nursery grounds for the early life stages of various fishes. Here, we compared the growth activity of fish larvae among 15 taxonomic groups, including 11 families in the Kuroshio and its neighbouring waters, based on protein synthetase activity and protein contents. Protein-specific (spAARS), individual-based aminoacyl tRNA synthetase activities (iAARS), and protein contents (PRO) of fish larvae ranged from 2 to 232 nmol PPi mg protein−1 h−1, from 1 to 21 μmol PPi ind−1 d−1, and from <1 to 26 mg ind−1, respectively. spAARS, iAARS and PRO were variable among the taxonomic groups and were not classified between mesopelagic groups and the others. Compiling these measurements among all taxonomic groups, a significant negative correlation was found for spAARS to PRO. The correlation showed no significant difference between the Kuroshio and its neighbouring coastal waters, indicating that growth activities to fish larvae body mass were comparable in the Kuroshio and its neighbouring waters. Based on nonmetric multidimensional scaling on spAARS, iAARS and PRO among 15 taxonomic groups, two different groups were classified for fish larvae, represented by the high iAARS under the high PRO but low spAARS (Group 1) and the low iAARS under the low PRO but high spAARS (Group 2), representing the different life strategies for larval growth among the taxonomic groups. The present findings suggest that these biochemical indices are useful for evaluating the growth activity of fish larvae among various taxonomic groups and that food availability is not poor enough to support larval growth in the Kuroshio and its neighbouring waters.

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Research Information
Prize of the Plankton Society of Japan
New Doctoral Recipients
Abstracts of Original Papers on Plankton & Benthos Research
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