NIPPON SUISAN GAKKAISHI
Online ISSN : 1349-998X
Print ISSN : 0021-5392
ISSN-L : 0021-5392
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Volume 71, Issue 6
Displaying 1-29 of 29 articles from this issue
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  • Food selectivity of seven-band grouper Epinephelus septemfasciatus larvae fed different sizes of rotifers
    YUKARI TANAKA, YOSHITAKA SAKAKURA, HISASHI CHUDA, ATSUSHI HAGIWARA, SU ...
    2005 Volume 71 Issue 6 Pages 911-916
    Published: 2005
    Released on J-STAGE: December 05, 2005
    DOIhttps://doi.org/10.2331/suisan.71.911
    JOURNAL FREE ACCESS
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      We investigated feeding selectivity on different sizes of rotifers (lorica length 90-241 μm) of seven-band grouper Epinephelus septemfasciatus larvae. Larvae ranging from 2.0 mm in standard length (SL, first feeding) to 3.0 mm SL positively selected 101-160 μm rotifers, while larvae ranging from 3.0-4.0 mm SL selected 121-180 μm rotifers. Fish bigger than 4.0 mm SL showed a preference for over 160 μm rotifers. In seedling production of this species, small-sized rotifers (<160 μm) are necessary during the first feeding (<3.0 mm SL), and large-sized rotifers (≧160 μm) are appropriate for larvae bigger than 3.0 mm SL.
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  • The early detection of Olpidiopsis sp. (Oomycetes, Chromista) which causes damage to Nori cultivation using a PCR.
    KAZUNARI YOKOO, SATOSHI SEKIMOTO, YOSHIO KAWAMURA, DAISUKE HONDA
    2005 Volume 71 Issue 6 Pages 917-922
    Published: 2005
    Released on J-STAGE: December 05, 2005
    DOIhttps://doi.org/10.2331/suisan.71.917
    JOURNAL FREE ACCESS
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      Chytrid disease, which is caused by Olpidiopsis sp., damages Nori cultivation every year. We have developed a polymerase chain reaction (PCR) based technique for the detection of Olpidiopsis sp. from the seawater in Nori culture farms. The PCR primers used here are Olpidiopsis sp. specific and encompass a 420 bp (1st PCR) and 256 bp (2nd PCR) region from the 18S rDNA gene of Olpidiopsis sp. The PCR was performed using supernatant seawater, after incubating for 60 minutes in seawater of 35 psu salinity. Zoospores of Olpidiopsis sp. were detected 14 days before detection by bio-assay method, and 33 days before finding by inspection under a microscope. From the results, the technique developed in the present study is useful for the early detection of Olpidiopsis sp. in the field.
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  • Ability of Amphiascus sp. (Copepoda, Harpacticoida) to remove fouling diatoms on conchocelis-bearing oyster shells in nori culture
    TAKAYUKI MINE, YOSHIO KAWAMURA, HIROSHI UEDA
    2005 Volume 71 Issue 6 Pages 923-927
    Published: 2005
    Released on J-STAGE: December 05, 2005
    DOIhttps://doi.org/10.2331/suisan.71.923
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      Shell-boring conchocelis of nori Porphyra was incubated for 6 weeks with a harpacticoid copepod Amphiascus sp., which is sometimes observed to propagate in cultivation tanks of the conchocelis, to evaluate the ability of the copepod to remove fouling diatoms on the shells. In the control tank without the copepod, diatoms on the shells increased exponentially and changed the white color of the shells to brown during the experiment. The density of the copepods including nauplii on the shells increased to 5.3 animals/cm2 for 6 weeks of culture. They suppressed the amount of fouling diatoms to about 1/6 of that in the control tank at the end of the experiment and the shell color was not changed except for the marginal area of the shell. Conchocelis after 6 weeks of culture was significantly longer in the experimental tank than in the control tank although its length was not different between the tanks for the initial 5 weeks. The nutrient concentrations such as PO4 dropped more in the control tank. These results indicate that the copepod can effectively remove fouling diatoms from conchocelis-bearing shells, and so adding this copepod in conchocelis-culture tanks may reduce shell-cleaning labor in nori culture.
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  • Light perception capability of pallial eyes in Japanese moon scallop Amusium japonicum as determined by electroretinogram
    TOYOMI KANMIZUTARU, KAZUHIKO ANRAKU, SHOUJI TOYODA
    2005 Volume 71 Issue 6 Pages 928-934
    Published: 2005
    Released on J-STAGE: December 05, 2005
    DOIhttps://doi.org/10.2331/suisan.71.928
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      Electroretinograms (ERGs) were recorded from the large and small pallial eyes of the scallop Amusium japonicum to determine their light perception capability. ERG recordings during the process from light to dark adaptations indicated that the light adapted eyes were completely adapted to the dark by 40 to 50 min, which was shorter than in fishes. Under two consecutive light stimulations at illuminances of 2.7 lx and 50 lx, the effect of the first stimulation on the second ERG response disappeared when the time interval between the two stimulations was longer than 20 s. Both eyes were sensitive to a wide range of spectra (433 to 700 nm) with a peak at around 470 to 520 nm, which was considered to be well adapted to the light environment of the shallow habitats of this species. ERGs were recorded under a flicker light of different flicker frequencies (0.05-10 Hz) to determine the critical fusion frequency (cff), which was 1.3 to 1.5 Hz. This much lower cff than found in fishes was considered to be due to adaptation for the detection of slow-moving objects.
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  • Length-based stock assessment and fisheries management of hair crab Erimacrus isenbeckii in Funka Bay, Hokkaido, Japan
    EIJI MIHARA, HIROSHI YAMAGUCHI, YUJI UEDA, TAKASHI MATSUISHI
    2005 Volume 71 Issue 6 Pages 935-941
    Published: 2005
    Released on J-STAGE: December 05, 2005
    DOIhttps://doi.org/10.2331/suisan.71.935
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      The hair crab fishery in Funka Bay, Hokkaido, has adopted a total allowable catch system. In order to examine management policy, a length-based population analysis (LPA) including yield per recruit (YPRL) was conducted on the hair crab in Funka Bay. LPA is effective for assessing fish stocks with uncertain aging characteristics. YPRL was developed for this study, as a method of calculating the YPR using parameters for each length class, which are estimated by LPA, instead of parameters for each age. The LPA model followed the population dynamics of this stock. Estimated abundance remained comparatively stable, but showed no recovery trend. As a result of YPRL, the fishing mortality coefficient, which is used for calculating total allowable catch, was 60% of F0.1, a sufficiently safe value. Consequently, we concluded that fisheries management should continue to be based on the existing reference points.
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  • Effects of oocyte diameter on ovulation time, quantity and quality of eggs in yellowtail Seriola quinqueradiata in inducing ovulation with HCG
    HISASHI CHUDA, TAKAHIRO NAKAO, TOSHIHISA ARAKAWA, MICHIYA MATSUYAMA
    2005 Volume 71 Issue 6 Pages 942-946
    Published: 2005
    Released on J-STAGE: December 05, 2005
    DOIhttps://doi.org/10.2331/suisan.71.942
    JOURNAL FREE ACCESS
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      Effects of initial oocyte diameter on ovulation time, quantity and quality of eggs in yellowtail, Seriola quinqueradiata, in inducing ovulation with HCG were examined. After measuring the oocyte diameter through ovarian biopsy, all fish (n=33) were divided into three groups according to their oocyte size: 650-700, 700-750, and 750-800 μm, and injected with HCG (500 IU/kg BW). Ovulation was induced in All the fish of the three groups, and the relationship between elapsed time until ovulation (T, hr) and oocyte diameter (D, μm) was represented as follows: T=-0.082D+105.99 (R2=0.51). 530 thousand eggs per fish could be obtained from fish with oocyte diameter over 700 μm, while only half the number of eggs could be collected from fish with oocyte diameter of 650-700 μm. High fertilization rates of over 90% could be obtained from all three groups regardless of the initial oocyte diameter when the artificial insemination had been performed just after ovulation. However, the hatching rates rose with the increase of initial oocyte diameter. Thus, measuring the initial oocyte diameter before the HCG injection enables estimation of the ovulation time, number and quality of ovulated eggs in yellowtail.
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  • Acoustic identification of scattering layer by Maurolicus japonicus around the Oki Islands, Sea of Japan
    TADANORI FUJINO, KAZUSHI MIYASHITA, ICHIRO AOKI, SHINYA MASUDA, RYOUSU ...
    2005 Volume 71 Issue 6 Pages 947-956
    Published: 2005
    Released on J-STAGE: December 05, 2005
    DOIhttps://doi.org/10.2331/suisan.71.947
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      We examined threshold-setting methods to identify Maurolicus japonicus SL (Scattering Layer) in the Sea of Japan. Acoustic survey data were collected in several months (May, June, Aug., Sep., and Oct.) from 2000 to 2003 around the Oki Islands, southwest of the Sea of Japan. The results showed the following threshold-setting method to be appropriate: to set the value as the lower limit SV threshold obtained by subtracting 10 dB from the averaged maximum SV of the water column. The depth range extracted by this method matched the existence of M. japonicus confirmed by the bottom and midwater trawl sampling. This method corresponds to the change of packing density by seeking the threshold baseline from the M. japonicus SL.
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  • Gel forming ability of walleye pollack frozen surimi-protein and its concentration dependency
    SEIICHI KITAKAMI, YURIKO MURAKAMI, KOSAKU YASUNAGA, NOBORU KATO, KEN-I ...
    2005 Volume 71 Issue 6 Pages 957-964
    Published: 2005
    Released on J-STAGE: December 05, 2005
    DOIhttps://doi.org/10.2331/suisan.71.957
    JOURNAL FREE ACCESS
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      Frozen surimi was thawed, mixed with 10-150% water by weight, and the mixtures were ground with 3.0%NaCl. The salt-ground meats were preheated at 25°C and subsequently heated at 90°C for 30 min. Breaking strength (BS) and breaking strain (bs) of the gels were measured as a function of preheating time, and gel stiffness was calculated as Gs=BS/bs. The results were: (1) The maximum values of BS and Gs of the heated gels exponentially rose with the increase in protein concentration in the gels, whereas the increasing modes of bs values were different from with those of BS and Gs. However, it was clear that the maximum levels of all these measures were higher in the order of the gels from 2nd<2nd (special)<A<SA grade. (2) There was a close positive correlation between the maximum values of BS and Gs of the two-step heated gels ranging in protein concentration from 7 to 17%. The linear relations and their slopes were different depending on the grades of frozen surimi.
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