NIPPON SUISAN GAKKAISHI
Online ISSN : 1349-998X
Print ISSN : 0021-5392
ISSN-L : 0021-5392
Advance online publication
Displaying 1-7 of 7 articles from this issue
  • HIDEAKI YAMADA, IWAO TANITA
    Article type: Original
    Article ID: 23-00038
    Published: 2024
    Advance online publication: February 20, 2024
    JOURNAL FREE ACCESS ADVANCE PUBLICATION

     Zostera japonica is an intertidal seagrass with a wide latitudinal distribution extending from tropical to temperate zones. We examined the distributional characteristics of Z. japonica in a subtropical intertidal zone. In a lagoon-like calm area with low current velocity and short emersion duration, Z. japonica had long vegetative shoots, high above-ground and below-ground biomasses, and sparse shoot density, compared to those in sites around the upper and lower distributional limits. At sites around the upper and lower distributional limits, shoot length of vegetative shoots, as well as above-ground and below-ground biomasses, showed moderate differences between June 2019 and February 2021. In the main distribution area with dense meadows, shoot length and above-ground biomass reached maximum values during June to August, while total shoot density increased during the winter season, suggesting that the above-ground biomass mainly depends on shoot length. The density of reproductive shoots indicated a high value only in February, implying that sexual reproduction occurs during a short duration around the lowest temperature period. Therefore, the progress of global warming may cause a decline of reproductive effort in subtropical populations.

    Download PDF (1691K)
  • TOMOYA YOSHIMITSU, TADASHI TOKAI, DAISUKE SHIODE, FUXIANG HU
    Article type: Original
    Article ID: 23-00042
    Published: 2024
    Advance online publication: February 20, 2024
    JOURNAL FREE ACCESS ADVANCE PUBLICATION
    Supplementary material

     Research gillnets use combinations of different gillnet mesh sizes to avoid the effect of mesh selectivity on the body length distribution of fish caught. In this study, pooled relative sampling efficiencies (PRSEs) for body length were obtained by assuming various gillnet selectivity curve parameters when the common ratio or common differences between mesh sizes were held constant in the available gillnet mesh sizes for research gillnets, and the conditions under which the PRSEs were kept nearly constant over the length range of target fish species for survey were examined. As a result, the PRSEs for body length were observed to be constant to some extent only when the common ratio between mesh sizes remained constant in the cases of gillnet selectivity parameters with large optimum relative length (6.0 to 7.0) and a medium 50%-selection relative length range (2.5 to 4.5). In the cases of narrow 50%-selection relative length range, the PRSEs for body length often showed a multimodal shape. Possible countermeasures in such cases include using a smaller common ratio between mesh sizes, adjusting the number of gillnets of a given mesh size, or correcting the length composition of the fish caught by mesh selectivity.

    Download PDF (1557K)
  • GO KATAYOSE, NAOSHI SATO, TAKASHI ASAHIDA
    Article type: Original
    Article ID: 23-00043
    Published: 2024
    Advance online publication: February 20, 2024
    JOURNAL FREE ACCESS ADVANCE PUBLICATION

     The sandy surf zone at Urahama beach was substantially altered on 11 March 2011, as a result of a powerful tsunami and land subsidence. Although the zone disappeared immediately after the tsunami, a rejuvenated sandy beach and intertidal area emerged a few months later. Prior to the tsunami, 9 orders, 27 families, and 41 species of larval and juvenile fish were collected using a seine net from January 2003 to December 2005. The dominant species of larval and juvenile fishes primarily comprised eurythermal and cold-water species, reflecting the geographical characteristics of the larval and juvenile fish fauna. Nonmetric multidimensional scaling results revealed seasonal changes in the species composition. Post-tsunami, at least 44 species of larval and juvenile fishes were collected during 2012–2015, with this collection indicating changes in species composition and an increase in the diversity index. These findings were supported by cluster analysis results, based on Jaccard’s coefficient of community, and the ecological characteristics of the dominant species. Overall, these results suggest that environmental changes, particularly the increased introduction of stones and seaweeds in the new intertidal area, markedly influenced changes in larval and juvenile fish fauna.

    Download PDF (1710K)
  • EIJI TANAKA
    Article type: Original
    Article ID: 23-00050
    Published: 2024
    Advance online publication: February 20, 2024
    JOURNAL FREE ACCESS ADVANCE PUBLICATION

     Theoretical models of monthly catch and stock size in weight were derived using a continuous recruitment model and the models were applied to monthly data of catch and catch per unit effort (CPUE) for the stock of white shrimp Pasiphaea japonica in Toyama Bay in order to estimate annual stock size of the shrimp from 2012 to 2021. Unknown parameters were estimated by simultaneously minimizing the residual sum of squares (RSS) of the catch data and RSS of the CPUE data. Estimates of the annual average of stock size were increasing. Estimated rates of annual catch to sum of weight of annual recruits and stock size at the beginning of the year were 0.53 in 2013 and 0.33 in 2021; the rates were gradually decreasing. Recruitment peaked in July and from November to December. The results and modification of the estimation are discussed.

    Download PDF (983K)
  • TAKAO HAYASHIDA, KOGEN OKITA, KENTARO HIGUCHI, HIROSHI HASHIMOTO, TAKE ...
    Article type: Short Paper
    Article ID: 23-00052
    Published: 2024
    Advance online publication: February 07, 2024
    JOURNAL FREE ACCESS ADVANCE PUBLICATION
  • ATSUSHI IKEGAMI, YUTO SASAKI, YUKI TAKAHASHI, HITOSHI MAENO, SHIGERU A ...
    Article type: Short Paper
    Article ID: 23-00023
    Published: 2024
    Advance online publication: February 07, 2024
    JOURNAL FREE ACCESS ADVANCE PUBLICATION
  • KEIGO YAMAMOTO, HIROSHI OIKAWA
    Article type: Original
    Article ID: 23-00039
    Published: 2024
    Advance online publication: February 07, 2024
    JOURNAL FREE ACCESS ADVANCE PUBLICATION

     Ark shell and Japanese cockle collected in 2014 and 2015 were dissected into four parts (muscle, mantle/adductor, gill, and viscera) and paralytic shellfish toxins contained in each part were analyzed. In ark shell, paralytic shellfish toxins were distributed in all four parts and were abundant in the muscle, mantle/adductor and viscera. In Japanese cockle, the toxins were abundant in the gill and viscera, and very low in the muscle. The percentage of toxic components was high in GTX2 and GTX3 in both species. In ark shell, STX tended to be high in the early stage of poisoning as well, except in the viscera. STX in Japanese cockle was high only in the gill. These results suggest that in ark shell, the toxic components diffuse from the viscera to the whole body shortly after causative toxic algae appeared, whereas in Japanese cockle, the toxic components migrate only to the gills where they are converted to STX.

    Download PDF (2168K)
feedback
Top