NIPPON SUISAN GAKKAISHI
Online ISSN : 1349-998X
Print ISSN : 0021-5392
ISSN-L : 0021-5392
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Volume 88, Issue 1
Displaying 1-14 of 14 articles from this issue
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Foreword
Originals
  • Estimation of predation mortality rates of the Pacific stock of Japanese anchovy by the Pacific stocks of mackerel
    EIJI TANAKA
    Article type: Originals
    2022 Volume 88 Issue 1 Pages 2-11
    Published: January 15, 2022
    Released on J-STAGE: February 02, 2022
    Advance online publication: November 26, 2021
    DOIhttps://doi.org/10.2331/suisan.20-00067
    JOURNAL FREE ACCESS
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    　Virtual population analysis (VPA) was applied to data of the Pacific stock of the Japanese anchovy Engraulis japonicus in order to estimate its annual rate of predation mortality by the Pacific stocks of chub mackerel Scomber japonicus and spotted mackerel Scomber australasicus. Data used in this analysis were catch-at-age and absolute abundance estimates by egg production survey for the anchovy stock from 1995 to 2018, and existing biomass estimates of the two stocks of mackerel. The natural mortality coefficient of the anchovy stock is assumed to be a linear function of the sum of biomass of the mackerel stocks. Unknown parameters are estimated by maximizing log-likelihood using the abundance estimates and theoretical ones by VPA with the constraint that the mean of natural mortality coefficients over the years is equal to the empirical value of the coefficient used in past studies. The results showed that estimates of the annual rate of predation mortality increased from 0.06 (per year, 95%CI: 0.03-0.09) in 1995 to 0.43 (0.28-0.54) in 2018. Appropriateness of the estimates and future data collection for incorporating predation into models of natural mortality were discussed.

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  • Phenology and environmental characteristics of two Sargassum species (Fucales), S. hemiphyllum and S. glaucescens, from Kagoshima Bay, Japan
    TAKAHIRO KURAHORI, HIROMORI SHIMABUKURO, TADAMITSU IGARI, RYUTA TERADA
    Article type: Originals
    2022 Volume 88 Issue 1 Pages 12-19
    Published: January 15, 2022
    Released on J-STAGE: February 02, 2022
    Advance online publication: November 26, 2021
    DOIhttps://doi.org/10.2331/suisan.21-00028
    JOURNAL FREE ACCESS
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    　The phenology and environmental characteristics of two brown algae, Sargassum hemiphyllum and S. glaucescens (Fucales), were investigated at Yamagawa, Ibusuki, Kagoshima Bay, Japan. Their vertical distributions in the upper subtidal zone were determined using the line transect method. The two species were found on the rocks and cobbles at a depth of 2 m in the upper subtidal zone. S. hemiphyllum (Sh) occurred at a slightly shallower depth than S. glaucescens (Sg). The two species grew well in February as the seawater temperature reached its lowest at 14℃, and Sh reached a maximum length of more than 2 m in May and matured in June. In contrast, Sg matured in July through August with a maximum length of 1.5 m, suggesting that their maturation periods were slightly different. After the maturation of Sh, new primary laterals (branches and leaves) for the next year's growth were already present; however, other parts including branches, leaves, vesicles, and receptacles that had emerged previously were completely withered by the end of summer. As for Sg, whole portions including the rhizoids were withered after their maturation, indicating the disappearance of large Sargassum assemblages from the study site during the summer through early winter.

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Short Paper
Highlights in Fisheries Science Research
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Abstracts of Original Papers
Letter from Board of Directors
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