NIPPON SUISAN GAKKAISHI
Online ISSN : 1349-998X
Print ISSN : 0021-5392
ISSN-L : 0021-5392
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Volume 75, Issue 5
Displaying 1-50 of 61 articles from this issue
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Technical Achievement Award in Fisheries Science 2008
Originals
  • Diel differences of catch, and swimming behavior in willowy flounder Tanakius kitaharai
    KUNIHIRO FUJIWARA, TOSHIAKI MIYAJIMA, ATSUSHI YAMASAKI
    2009 Volume 75 Issue 5 Pages 779-785
    Published: 2009
    Released on J-STAGE: January 17, 2010
    DOIhttps://doi.org/10.2331/suisan.75.779
    JOURNAL FREE ACCESS
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      This paper describes the diurnal differences of catch trends and behavioral patterns of willowy flounder Tanakius kitaharai. A beam-trawl net equipped with an underwater video camera was used to investigate these changes in the T. kitaharai population off Tango Peninsula. The catch was smaller in the daytime than at night. The video footage revealed that approximately 80% of observed individuals swam at night and approximately 90% were at rest during the day. These results suggest that individuals of this species are rarely caught when they are settled on the sea bed. Therefore, the T. kitaharai catch in a beam-trawl net carried out during the day and catch efficiency during the night would underestimate the actual resources of this species.
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  • Toxicity and antibacterial activity of silver ions in the rearing water of Japanese eel eggs and larvae
    AKIHIRO OKAMURA, YOSHIAKI YAMADA, NORIYUKI HORIE, NAOMI MIKAWA, TOMOKO ...
    2009 Volume 75 Issue 5 Pages 786-792
    Published: 2009
    Released on J-STAGE: January 17, 2010
    DOIhttps://doi.org/10.2331/suisan.75.786
    JOURNAL FREE ACCESS
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      To apply the antibacterial activity of silver ions to the rearing of Japanese eel Anguilla japonica larvae, we tested the effects of exposure to silver ions on hatching, survival and growth in eel larvae. Hatching rate of eggs was significantly decreased at a silver nitrate concentration of higher than 0.1 mg/L in rearing water (p<0.01), whereas the survival rates of 0 or 5-day-old larvae were not influenced by exposure to the same condition for 120 hours. However, the survival rates of those larvae were decreased by exposure to 1 mg/L silver nitrate for more than 24 hours. During long-term rearing experiments, the number of bacteria on the wall of the rearing tank was significantly reduced by intermittently (four times a day) adding silver nitrate (max. 1 mg/L) to rearing water, and larval survival rate at the early stage (5 to 60-day-old) became significantly higher than that in the normal rearing method (p<0.05). Growth was not influenced by adding silver nitrate, and six larvae in the silver-added tank finally metamorphosed into glass eels without any morphological anomalies. These results suggest that the use of silver ions in rearing eel larvae can facilitate the efficient production of artificial glass eels.
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  • Model test of trawl gear with a net-mouth opening device based on modified Tauti's law
    TAISEI KUMAZAWA, FUXIANG HU, SHIGERU FUWA, KIMIAKI NAGAMATU, HIROMI KI ...
    2009 Volume 75 Issue 5 Pages 793-801
    Published: 2009
    Released on J-STAGE: January 17, 2010
    DOIhttps://doi.org/10.2331/suisan.75.793
    JOURNAL FREE ACCESS
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      For model testing of trawl gear utilizing an opening device such as an otter board, the ratio in area of the model opening device to the full-scale device was proposed based on modified Tauti's law. A sea trial with a full-scale midwater trawl net of 27.44 m in total length and model experiment with 1/10 scale model were conducted. Two otter board models of different scale were used for the model experiment: otter board model I of 1/60 area scale based on the modified Tauti's law, and model II of 1/100 area scale based on the original Tauti's law. As a result, a distinct difference both in the distance of the two otter boards and in net-mouth height was found between the converted values from the model test with model II based on Tauti's law and the observed values in the full-scale sea trial. In contrast, no such difference was observed in the results of model I. In addition, it was verified that the speed ratio based on the modified Tauti's law was useful for predicting the drag of the test trawl gear with opening device.
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  • Effects of adult white-spotted charr Salvelinus leucomaenis and masu salmon Oncorhynchus masou masou on focal points, distribution area and foraging frequency of both juveniles in a small tributary of a Japanese mountain stream
    TAKEHIKO UENO, YUUKI TANAKA, TAKASHI MARUYAMA
    2009 Volume 75 Issue 5 Pages 802-809
    Published: 2009
    Released on J-STAGE: January 17, 2010
    DOIhttps://doi.org/10.2331/suisan.75.802
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      We conducted experimental field observations to investigate the effects of the presence of adult white-spotted charr Salvelinus leucomaenis and masu salmon Oncorhynchus masou masou on the behavioral response of both juveniles in a small tributary of a Japanese mountain stream. Juveniles (small-size charr, large-size charr and large-size masu salmon) were released into three experimental areas, respectively, and their focal points, size of distribution area obtained with movement tracing and feeding frequency were recorded, under three treatments e.g., juvenile only, juvenile with an adult charr and juvenile with an adult masu salmon for each species. In only juvenile treatments, the focal points and distribution area spread all over the experiment areas for both species. In the presence of adult fishes, the focal points of juveniles shifted to near-shore margins which were significantly shallower and lower in water velocity. Moreover, the size of distribution area per fish and feeding frequency were decreased significantly. These results suggest that juveniles can be affected ecologically by the presence of adult fish in a small tributary of a Japanese mountain stream.
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  • Carbon flow through the food web established on an artificial fish reef
    KOICHI HARAGUCHI, TAMIJI YAMAMOTO, TAKAYUKI KATAYAMA, OSAMU MATSUDA
    2009 Volume 75 Issue 5 Pages 810-818
    Published: 2009
    Released on J-STAGE: January 17, 2010
    DOIhttps://doi.org/10.2331/suisan.75.810
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      Artificial fish reefs have been deployed in the inner part of Ago Bay, where intensive pearl oyster culturing occurs, in order to clarify the carbon flow through the food web and mineralization of organic matter on the reefs. The reefs consist of steel frame and polyethylene mesh cages in which pearl oyster shells are stuffed. The tops of the reefs are situated in the middle of the water column under the pearl oyster raft so that trapped organic particles decompose in aerobic conditions. We monitored carbon content in the sediments under the reefs in addition to benthic fauna and fish, for ca. 7 months during 2006-2007. Budget analyses revealed that decomposition of organic matter by macrobenthos respiration was 16-61% and removal of organic matter through the food web, in terms of feeding by top predators (e.g., fish), was 27-72% from summer through fall. In winter, however, the removal rate of organic matter decreased to 20-70% of that in the warm season. In conclusion, artificial fish reefs help reduce the organic matter in aquaculture areas via decomposition occurring in the water column and enhance the growth of top predators in the bay.
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  • Age at maturity, spawning season and spawning frequency of threeline grunt Parapristipoma trilineatum along the south-western coast of Kii Peninsula, Japan, as determined by gonadal histological observation
    RYU DOIUCHI, YO YOSHIMOTO
    2009 Volume 75 Issue 5 Pages 819-827
    Published: 2009
    Released on J-STAGE: January 17, 2010
    DOIhttps://doi.org/10.2331/suisan.75.819
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      The age at maturity, spawning season and spawning frequency of threeline grunt Parapristipoma trilineatum occurring along the south-western coast of the Kii Peninsula, Japan, were investigated. Histological observations of gonads demonstrated that no females at age 1 year and all females over 2 years were mature, compared with all males over 1 year. Seasonal changes in ovarian maturation, together with seasonal occurrence of postovulatory follicles, suggested that the spawning season in the region was from May to August, peak spawning occurring in June. Seasonal changes in gonadosomatic index (GSI) differed slightly from the former in females over 3 years, peaking in May and dropping in June, thereby indicating a rapid deposition of yolk from April to May, followed by highest spawning activity in June. Decreased GSI in June seemed attributable to the increased number of individuals in which gonad weight had temporarily decreased due to high spawning activity. The estimated spawning frequency in each month between May and August was 0.17, 0.51, 0.26 and 0.19, respectively.
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  • Effect of maternal diet on survival and life history parameters of next generations in the rotifer Brachionus plicatilis sp. complex
    MASAHIKO KOISO, MASAYO YOSHIKAWA, HIROSHI KUWADA, ATSUSHI HAGIWARA
    2009 Volume 75 Issue 5 Pages 828-833
    Published: 2009
    Released on J-STAGE: January 17, 2010
    DOIhttps://doi.org/10.2331/suisan.75.828
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      The effect of maternal diet on the survival rate and life history parameters of next generations in the rotifer Brachionus plicatilis sp. complex was investigated. Maternal rotifers as well as their offspring were individually cultured successively to the 5th generation in three feeding patterns, including the feeding of Nannochloropsis oculata alone (N), baker's yeast alone (Y), and feeding of baker's yeast to the 1st generation and N. oculata to the next generations (YN). In the Y-rotifers, survival rate, development time and spawning interval of the 1st and 2nd generations were significantly inferior to those of the N-rotifers, and all individuals died in the 3rd generation. As for YN-rotifers in the 2nd generation, survival rate decreased by 20% compared with N-rotifers, and development time and spawning interval were 1.1-1.2 times longer. These results suggest that the effect of maternal diet influenced even next generations by affecting the quality of amictic eggs.
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  • An artificial midlayer seafloor-Evaluation of reducing sinking particulate load from suspended oyster culture from an initial half-year observation
    TAMIJI YAMAMOTO, SHOHEI SASADA, KOICHI HARAGUCHI
    2009 Volume 75 Issue 5 Pages 834-843
    Published: 2009
    Released on J-STAGE: January 17, 2010
    DOIhttps://doi.org/10.2331/suisan.75.834
    JOURNAL FREE ACCESS
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      An artificial midlayer seafloor (AMS) was settled in July 2005 to promote aerobic decomposition of sinking organic matter from suspended oyster culture in Etajima Bay, Japan. The AMS consisted of a steel frame and polyethylene mesh cages in which oyster shells were stuffed. The top of the AMS was 3 m from the seabed so that organic particles from the suspended oyster culture decomposed under aerobic conditions. Particulate matter, benthic fauna and flora on the AMS as well as sediments under the AMS were monitored for 6 months from July 2005 to January 2006. During the first 4 months after deployment, carbon content in the sediments under the AMS was decreased. Based on the budget analyses of carbon, it was estimated that 6-8% of the sinking particulate carbon was trapped on the AMS and 5-10% was reduced by bacterial decomposition. As a result, it was estimated that 6-9% of sinking particulate carbon was reduced. From 5 months and onward, however, the removal rate of particulate matter decreased. This could be due to a decrease in bacterial decomposition activity in the winter season, and additional particulate load by increases in attached algae and suspension feeder on the AMS.
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  • Determination of the geographic origin of Japanese eel products by inorganic analysis
    SATOSHI HATTORI, YASUHARE KIMURA, YASUHARU TAKASHIMA, YUJI HOUMURA
    2009 Volume 75 Issue 5 Pages 844-848
    Published: 2009
    Released on J-STAGE: January 17, 2010
    DOIhttps://doi.org/10.2331/suisan.75.844
    JOURNAL FREE ACCESS
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      A technique to determine the geographic origin of Japanese eel products was developed based on the analyses of 250 samples from Japan and China. Five elements (Mn, Fe, Zn, Sr and Ba) in samples were determined by using inductively coupled plasma mass spectrometry (ICP-MS). We developed five linear discriminant analysis (LDA) models for each production ground calibrated with concentrations of elements chosen by backward stepwise regression. These LDA models distinguished the origin of eel products with 85-94% certainty, and with 85-93% certainty in the validation test by 10-fold cross validation.
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