NIPPON SUISAN GAKKAISHI
Online ISSN : 1349-998X
Print ISSN : 0021-5392
ISSN-L : 0021-5392
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Volume 74, Issue 4
Displaying 1-18 of 18 articles from this issue
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Achievement Award for Young Scientist in Fisheries Science 2007
Originals
  • Growth of the juvenile red snow crab Chionoecetes japonicus in Toyama Bay estimated from carapace width frequency distribution
    TSUNEO MAEDA, RYO TSUJIMOTO
    2008 Volume 74 Issue 4 Pages 592-597
    Published: 2008
    Released on J-STAGE: July 28, 2008
    DOIhttps://doi.org/10.2331/suisan.74.592
    JOURNAL FREE ACCESS
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      Red snow crab Chionoecetes japonicus were collected from the central part of Toyama Bay at the depth of about 1,000-1,250 m by a beam trawl in summer and winter from 2000 to 2006, in order to investigate their growth in the juvenile stage. Carapace width (CW) measurement revealed six modes of size-frequency distribution in the range of 5-40 mm CW in both males and females. Dividing into the six normal distributions, the mean size in CW in each one was estimated to be 6.4, 9.2, 13.3, 18.0, 25.4 and 33.7 mm in males, and 6.5, 9.0, 12.7, 17.9, 24.3 and 32.6 mm in females, which were thought to mean CW at the 3rd to 8th instars, respectively. There was a tendency for crabs in the 4th and 6th instars to occur dominantly in summer and in the 5th instar to do so in winter.
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  • Inhibitory effects of centric diatoms on the growth of the dinoflagellate Akashiwo sanguinea
    TADASHI MATSUBARA, SOU NAGASOE, YASUHIRO YAMASAKI, TOMOYUKI SHIKATA, Y ...
    2008 Volume 74 Issue 4 Pages 598-606
    Published: 2008
    Released on J-STAGE: July 28, 2008
    DOIhttps://doi.org/10.2331/suisan.74.598
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      Results of a four-year study on phytoplankton in Hakozaki Harbor, Hakata Bay, Japan indicated that Akashiwo sanguinea (Hirasaka) Hansen et Moestrup was the cause of frequent blooms during the late fall period when centric diatoms such as Skeletonema costatum and genus Chaetoceros declined. In laboratory experiments, the growth of A. sanguinea was found to be strongly inhibited in bi-algal cultures with S. costatum and Chaetoceros didymum, but just slightly with Asterionella japonica. Furthermore, when A. sanguinea was cultured in nitrogen and phosphorus enriched filtrates with media on which S. costatum and C. didymum had grown densely, the growth rate of A. sanguinea in the filtrates was significantly lower than that in fresh control medium. These results suggest that in spring and summer allelopathy of bloomed centric diatoms was an important factor that inhibited the growth of A. sanguinea but in the late fall when the cell density of these diatoms declined, A. sanguinea could form blooms.
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  • Characteristics of fractional phosphorus distribution in sediment of fish farming area at Lake Kasumigaura, Japan
    YUICHI ISHII, NOBUYUKI KOMATSU, SATOSHI HARIGAE, TOHRU YABE, KEIJI WAT ...
    2008 Volume 74 Issue 4 Pages 607-614
    Published: 2008
    Released on J-STAGE: July 28, 2008
    DOIhttps://doi.org/10.2331/suisan.74.607
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      The distribution of phosphorus fractions in bottom sediment at a fish (carp) farming area and a non-farming area in three shallow eutrophic lakes, Nishiura, Kitaura and Sotonasakaura, and the characteristics of sediment at a carp farming area were examined. The total fractional phosphorus content in sediments at the carp farming area was relatively high. The inorganic phosphorus fraction, especially HCl-reactive phosphorus (HCl-RP) and citrate-dithionite-bicarbonate-reactive phosphorus (CDB-RP), was high in the sediment of the carp farming area. According to principal component analysis for the content rate of six phosphorus fractions in sediment, the sediments of the carp farming area were interpreted as those of the non-farming area to which HCl-RP was added. It was suggested that the fish feed (fish meal) and/or excrement accumulated in sediment under the fish cage.
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  • Evaluation of the stocking efficiency of giant cuttlefish Sepia latimanus hatchlings through marking experiments
    SHIGEKI DAN, KATSUYUKI HAMASAKI, TAKASHI YAMASHITA, MASAKAZU OKA, SHUI ...
    2008 Volume 74 Issue 4 Pages 615-624
    Published: 2008
    Released on J-STAGE: July 28, 2008
    DOIhttps://doi.org/10.2331/suisan.74.615
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      To evaluate the stocking effectiveness of giant cuttlefish hatchlings, 25-62 thousand individuals were annually marked on the cuttlebones with Alizarin red S and stocked into Urasoko and Kabira Bays of Ishigaki Island, Okinawa, southernmost Japan from 2001 to 2003. The giant cuttlefish caught by small set-nets in the bays and the cuttlebones collected from a fish market and five coastal beaches were examined to detect the marked cuttlebones and to measure the growth of released individuals. Released cuttlefish were caught in the bays where they were released from autumn in the release year to the spring two years later, and the proportion of released cuttlefish in catches ranged from 4.5 to 18.0%. The cuttlebones with marks were mainly collected on the beaches around the release sites. Based on these results, recapture rates and the yield per released individual were estimated at 0.02-0.08% and 0.24-1.28 g, respectively.
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  • Temperature effects of rotifer Brachionus plicatilis mass culture on rearing efficiency of larval Japanese flounder Paralichthys olivaceus
    TSUTOMU TOMODA, MASAHIKO KOISO, YASUHIRO SHIMA
    2008 Volume 74 Issue 4 Pages 625-635
    Published: 2008
    Released on J-STAGE: July 28, 2008
    DOIhttps://doi.org/10.2331/suisan.74.625
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      This study investigated the suitable temperature for mass culture of the rotifer, Brachionus plicatilis, in order to optimize the rearing of Japanese flounder, Paralichthys olivaceus, in terms of larval growth and vitality. Two-day batch cultures of rotifers were prepared daily at three graduated temperatures (18°C, 23°C, 28°C). Rotifers were harvested on day 2 from the start of cultivation, and then enriched at 18°C, the same temperature as larval rearing. Rotifers were supplied to the flounder larvae until 19 days post hatching (dph) at each temperature. Rotifers cultured at 23°C and 28°C had higher ratios of immature individuals, and their physiological state (e.g. egg ratio) after enrichment was poor. During 15-20 dph, larvae fed rotifers cultured at 18°C showed higher performance in growth and morphological development than those fed rotifers cultured at 23°C and at 28°C. All groups of larvae at 20 dph were evaluated according to starvation tolerance tests, when the larvae that had been fed 28°C rotifers had the lowest survival (P<0.05). The thermal difference between rotifer mass culture and larval rearing had a large influence on the rearing efficiency of Japanese flounder larvae.
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  • Distribution of egg production of Japanese anchovy, Engraulis japonicus, in the Seto Inland Sea, Japan, from 1980 to 2005
    NAOAKI KONO, HIROMU ZENITANI
    2008 Volume 74 Issue 4 Pages 636-644
    Published: 2008
    Released on J-STAGE: July 28, 2008
    DOIhttps://doi.org/10.2331/suisan.74.636
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      Egg production of Japanese anchovy, Engraulis japonicus, in the Seto Inland Sea was estimated based on extensive egg census data from 1980 to 2005. The fluctuations in temporal and spatial distribution of anchovy egg production were analyzed to understand trends of adult stock and the relationship between egg production and sea surface temperature. From 1980 to 2005, the annual egg production in the Seto Inland Sea fluctuated between 153 trillion in 1993 and 1,146 trillion in 2002. Spawning occurred mainly for 5 months from May to September. Annual egg production was the largest in Iyo-Nada. Density of annual egg production was the largest in Osaka Bay. Anchovy eggs were detected in the SST range from 7.9 to 31.7°C, and more concentrated from 16.0 to 28.9°C. Mean SST from May to September tended to be lower than the 26-year mean from 1986 to 1993 and higher than in 1994 and after. The fluctuation of total egg production from May to September showed similar trends as that of the mean SST except for 1997 and 1998.
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  • Effects of photoperiod on survival, growth and feeding of seven band grouper Epinephelus septemfaciatus larvae
    KAZUHISA TERUYA, KENZO YOSEDA, MASAKAZU OKA, TOYOHIRO NISHIOKA, SYOJI ...
    2008 Volume 74 Issue 4 Pages 645-652
    Published: 2008
    Released on J-STAGE: July 28, 2008
    DOIhttps://doi.org/10.2331/suisan.74.645
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      The larvae of the seven band grouper Epinephelus septemfaciatus were reared until eight days post hatching in 500 L tanks under four different photoperiods: 24L:0D, 12L:12D, 6L:6D:6L:6D, and 0L:24D. Further, mass-culture experiments of the seven band grouper larvae were conducted until ten days post hatching using 100 kL tanks under natural photoperiod and 24L:0D conditions. The number of rotifers in larval guts and total length of larvae were examined at six-hour intervals. The best survival and growth of larvae were observed in 500 L tanks with 24L:0D photoperiod. In addition, larval survival rate was better in the 100 kL tank under the constant light condition. The seven band grouper larvae were suggested to be a visual feeder and their gut contents were clearly observed in tanks with 24L:0D photoperiod even during dark phases in other tanks. Therefore, it is considered that improved survival and/or growth of larvae in tanks under the constant light condition are attributed to the prolonged feeding period for larvae.
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  • Effects of ozonized seawater and povidone iodine on hatching rate of Japanese flounder Paralichthys olivaceuseggs
    KENGO OHTA, MASATO ARITAKI, KEN-ICHI WATANABE
    2008 Volume 74 Issue 4 Pages 653-659
    Published: 2008
    Released on J-STAGE: July 28, 2008
    DOIhttps://doi.org/10.2331/suisan.74.653
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      Effects of ozone produced residual oxidants and povidone-iodine on hatching rates of Japanese flounder eggs were examined. The morula stage eggs collected both in May and June during the spawning period were exposed to ozonized seawater including oxidants (total residual oxidants: TROs) at concentrations ranging from 0.1 to 1.0 mg/L for a period from 1 to 15 min.
       They were also exposed to seawater including povidone-iodine at concentrations ranging from 25 to 75 mg/L as available concentration of iodine (ACI) for the same period as the ozonized seawater. The hatching rate of eggs collected in May was nearly identical with that of the control eggs (p<0.05) when tested eggs were exposed to oxidants of less than 1.0 mg/L for 2 min, or to iodine of less than 75 mg/L of ACI for 15 min. On the other hand, the hatching rate of eggs collected in June was lower than that of eggs collected in May under the same test conditions. These results suggest that safe hatching conditions are influenced by the spawning phase. Safe treatment conditions for Japanese flounder eggs are TROs of 0.5 mg/L for 5 min and ACI of 50 mg/L for 15 min.
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  • Bloom of a large diatom Chaetoceros densus in the coastal area of Kagawa Prefecture from Harima-Nada to Bisan-Seto, the Seto Inland Sea, in February 2005: environmental features during the bloom and influence on Nori Porphyra yezoensis cultures
    KENICHI OYAMA, SADAAKI YOSHIMATSU, KEIJI HONDA, YUKITOSHI ABE, TOKISHI ...
    2008 Volume 74 Issue 4 Pages 660-670
    Published: 2008
    Released on J-STAGE: July 28, 2008
    DOIhttps://doi.org/10.2331/suisan.74.660
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      A large diatom Chaetoceros densus bloomed in the coastal area of Kagawa Prefecture from Harima-Nada to Bisan-Seto, the Seto Inland Sea, in February 2005. The maximum cell density of C. densus 90,000 cells/L was recorded in Harima-Nada in mid February. With the increase of this species, nutrients decreased rapidly in the area. Discoloration of Nori, Porphyra yezoensis, occurred mainly at Nori cultures in Harima-Nada. Nutrient levels were as high as or higher than those of typical years until the bloom event. Salinity was remarkably lower during the event than in typical year. This is the first report on the discoloration of cultured Nori caused by blooming of C. densus through nutrient depletion. Careful monitoring of plankton is needed for the prediction of blooming because even minor species may become dominant and cause bleaching of cultured P. yezoensis.
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  • Development of high-speed salting method for boiled and salted Undaria pinnatifida and Laminaria religiosa
    MUNENAKA ONODERA, YUMIKO YOSHIE-STARK, TAKESHI SUZUKI
    2008 Volume 74 Issue 4 Pages 671-677
    Published: 2008
    Released on J-STAGE: July 28, 2008
    DOIhttps://doi.org/10.2331/suisan.74.671
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      There was a negative correlation between water activity (aw) and NaCl content/moisture of boiled and salted Uudaria pinnatifida and Laminaria religiosa. Boiled and salted Uudaria pinnatifida processed by the recommended method to prolong the shelf life showed aw of 0.76 and NaCl content of 18.0%. It should be possible to evaluate sodium chloride content and water content by aw analysis. To shorten the processing time and to obtain uniform quality of seaweed products, the salting method in saturated solution was performed in this study. It took 48 hours and 18 hours to obtain sufficiently low aw of salted U. pinnatifida and L. religiosa by soaking in saturated NaCl solution. With mechanical stirring of the saturated NaCl solution for treating the seaweeds, only 1 hour was required to reach aw of 0.75. This salting method with stirring will shorten the salting time, and enable safe products to be provided.
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  • Denitrification and nitrogen fixation rates at tidal flats and coastal bottom areas
    TOHRU SEIKI, ETSUJI DATE, MITSUMASA OKADA
    2008 Volume 74 Issue 4 Pages 678-687
    Published: 2008
    Released on J-STAGE: July 28, 2008
    DOIhttps://doi.org/10.2331/suisan.74.678
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      We investigated both rates of denitrification and N2 fixation using intact sediment cores at tidal flats and coastal bottom areas, and the relationships between their activities and environmental factors, to clarify their roles on nitrogen budget in northern Hiroshima Bay. Foreshore tidal flats in islands acted as net sources of nitrogen for the adjacent aquatic environments for these two processes of denitrification and N2 fixation, because the rates of the latter were almost higher than those of the former. It is considered that this phenomenon represents a characteristic of tidal flats located in islands, where nitrate concentrations in the surrounding environmental waters are low. However, other tidal flats at estuaries in mainland areas demonstrated reverse relations: denitrification rates were always higher than N2 fixation rates, and coastal bottom areas also acted as a net sink on nitrogen budget as well as the estuarine tidal flats, showing that these places played important roles in removing nitrogen from surrounding aquatic environments through these two processes.
       In situ rates of denitrification and N2 fixation were in the ranges of 0.01-20, 0.01-3.8 mg-N m-2 d-1 at tidal flats, and 0.10-3.4, 0.08-0.59 mg-N m-2 d-1 at coastal bottom areas, respectively. Between in situ rates of denitrification (DN) and N2 fixation (FN), there was a negative allometric power relation expressed as the following equation: FN=0.32 DN-0.318. N2 fixation rates were significantly correlated with water temperatures, and denitrification rates also showed highly significant correlations to ambient nitrate concentrations in environmental waters. Denitrification abilities measured under the same incubation conditions in 0.5 mg-N l-1 of nitrate at 20°C did not show any significant correlations with numbers of denitrifying bacteria, differences in types of tidal flats and sediment qualities, but did with the density and biomass of macrobenthos. This suggests that benthos may have some important influences on the activities of denitrifying bacteria.
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  • Development of coagulant for dredging using sea alga; Preparation of algal paste and its coagulating effect for muddy water
    MAKIKO ENOKI, MICHISUKE SATO, KODAI KANEDA, RYOTA SEKIYAMA, AKIKO NAKA ...
    2008 Volume 74 Issue 4 Pages 688-693
    Published: 2008
    Released on J-STAGE: July 28, 2008
    DOIhttps://doi.org/10.2331/suisan.74.688
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      Sea algal paste was obtained by soaking brown alga in sodium carbonate solution and was found to have a flocculating effect on muddy water in the presence of calcium chloride as a cross linking agent. This technique does not involve the extraction of alginic acid and production of secondary waste. The sea alga paste obtained by soaking in sodium carbonate solution for five minutes at 70°C demonstrated an excellent flocculating effect, which did not depend on the density of muddy water. Stirring time after mixing all ingredients was found to affect the flocculation. Furthermore, the amount of sea alga paste and calcium chloride also influenced the coagulating effect.
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