NIPPON SUISAN GAKKAISHI
Online ISSN : 1349-998X
Print ISSN : 0021-5392
ISSN-L : 0021-5392
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Volume 82, Issue 1
Displaying 1-26 of 26 articles from this issue
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Foreword
Originals
  • Habitat use and diet of larvae and juveniles of the goby Tridentiger brevispinis in the profundal and littoral zones in Lake Kitaura, Ibaraki Prefecture, Japan
    WATARU HYAKUNARI, MAO SHIBATA, KOUKI KANOU, SEIJI USUI, SEIYA KANEKO, ...
    2016 Volume 82 Issue 1 Pages 2-11
    Published: 2016
    Released on J-STAGE: February 03, 2016
    Advance online publication: December 22, 2015
    DOIhttps://doi.org/10.2331/suisan.15-00047
    JOURNAL FREE ACCESS
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     The goby Tridentiger brevispinis is a common benthic fish in the lakes and swamps of temperate Japan and is commercially important for local fisheries. The distribution, migration and food habits of larvae and juveniles of the species in Lake Kitaura, Ibaraki Prefecture, central Japan were investigated in the profundal (6-7 m depth) and littoral (0.5-1 m depth) zones, from April 2010 to March 2012. Within a few days of hatching, preflexion larvae were dispersed throughout the surface and middle layers in the profundal zone, pelagic juveniles thereafter aggregating in the bottom layer. Newly-settled and benthic juveniles subsequently migrated from the profundal to the littoral zone. The major food components of juveniles changed from planktonic (cladocerans and cyclopoid copepods) to benthic items (gammaridean amphipods, chironomid larvae and filamentous algae) with the inshore migration. Analyses of the relationships between benthic juvenile density and a variety of environmental variables in the littoral zone, using generalized linear models, indicated that the depth of undercut bank at the reed belt edge and the mud content of sediment were the most significant determinants of juvenile densities. This suggested that reed belts in the littoral zone are an important nursery habitat for benthic juveniles of the goby.
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  • Essential characteristics of aquatic environment for ayu habitats
    JUN-ICHI TSUBOI, YUYA TAKAGI
    2016 Volume 82 Issue 1 Pages 12-17
    Published: 2016
    Released on J-STAGE: February 03, 2016
    Advance online publication: December 25, 2015
    DOIhttps://doi.org/10.2331/suisan.15-00027
    JOURNAL FREE ACCESS
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     We investigated essential factors of the establishment of stocked ayu, Plecoglossus altivelis by going underwater with a snorkel to count the number of ayu individuals and measure the microhabitat in 25 rivers in Hokkaido, Honshu, and Kyushu. In our analysis, three factors were selected as explanatory variables for the number of ayu observed: 1) smaller river width, 2) higher frequency of boulders (over 25 cm in major axis) on the river bed, and 3) higher frequency of exposed boulders. These factors should be taken into account when making management decisions on stocking sites. The number of ayu individuals observed by snorkeling also positively correlated with catch per unit effort of “Tomozuri” angling in the Naka River. Therefore, the number of individuals counted by underwater observation may be an appropriate index of the abundance of ayu as a target for angling.
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  • Effect of cross breeding with domesticated males on smolting in masu salmon Oncorhynchus masou
    KAZUMASA OHKUMA, KATSUYA FUKUDA, TADAYOSHI TOJIMA, IKUO ONO
    2016 Volume 82 Issue 1 Pages 18-27
    Published: 2016
    Released on J-STAGE: February 03, 2016
    Advance online publication: December 25, 2015
    DOIhttps://doi.org/10.2331/suisan.15-00036
    JOURNAL FREE ACCESS
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     The rehabilitation of masu salmon resources, which have been declining for a long time, is strongly desired by coastal fishermen, especially in the Japan Sea region of northern Japan. Meanwhile, inland fisheries cooperatives release large numbers of riverine masu salmon, so-called “yamame”, which have been domesticated through many generations and show high growth and low smolting rates. Genetic contamination and the resulting reduction of smolting rate by the supposed cross-breeding of native anadromous female masu with the released male yamame are a serious issue. In this study, we experimentally bred anadromous female masu and male yamame, to investigate the effects on the smolting ratio. Regarding the maturation rate for young of the year (YOY) males, a higher rate was found in the Okutama-bred (OKT) group in five out of six compatible pairs, of which three were statistically significant (p<0.05, chi-square test). As for the smolting ratio of male fish, the Chitose-bred(CTS) group showed a higher rate than the OKT group in all six pairs, and five pairs were significantly different (p<0.01, chi-square test). Among the CTS group, almost all female fish were smoltified in every group, and the smolting rate of each group reflected the difference in smolting rate of male fish.
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  • Effects of bleeding on the volatile flavor compounds in skipjack tuna
    SEIICHI HIRATSUKA, YOSHITAKA HANEDA, KYOKO KOIZUMI
    2016 Volume 82 Issue 1 Pages 28-32
    Published: 2016
    Released on J-STAGE: February 03, 2016
    Advance online publication: December 22, 2015
    DOIhttps://doi.org/10.2331/suisan.15-00042
    JOURNAL FREE ACCESS
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     The volatile flavor compounds in ordinary muscles with and without bleeding of skipjack tuna Euthynnus pelamis were analyzed by gas chromatograph-mass spectrometry (GC/MS) and compared. The contents of aldehydes and alcohols in ordinary muscle of skipjack tuna with bleeding were significantly lower (p<0.05) than those without bleeding. The aldehydes and alcohols were generated when the blood and lipid separated from the skipjack tuna were incubated in phosphate buffer (pH 6.0) for 2 days at 5°C. However, they were not generated in one side of blood and lipid. The aldehyde and alcohol levels both increased with blood concentration in the range from 0 to 100 μL by the reaction of 100 mg of lipid. These results suggest that the aldehydes and alcohols from the skipjack tuna might be generated by the reaction of blood and lipid. Moreover, the bleeding of skipjack tuna could be effective for reducing fish odor.
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Abstracts of Original Papers
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