NIPPON SUISAN GAKKAISHI
Online ISSN : 1349-998X
Print ISSN : 0021-5392
ISSN-L : 0021-5392
Volume 71, Issue 1
Displaying 1-13 of 13 articles from this issue
Originals
  • TERUMI NAGAI, SATOSHI OTANI, TAIJU SAITO, SHINGO MAEGAWA, KUNIO INOUE, ...
    2005 Volume 71 Issue 1 Pages 1-9
    Published: 2005
    Released on J-STAGE: June 08, 2005
    JOURNAL FREE ACCESS
      To elucidate the effects of blastoderm graft for chimeric-fish production on further development, transplantations of upper, lower or entire part of blastoderm were performed onto the animal part of host embryos during the blastula stage in zebrafish. In the case of upper, all resultant chimeric embryos developed normally, while in the lower part, many acephalic embryos appeared. When the entire blastoderm was transplanted, many resultant embryos showed normal phenotype with extra cell-mass, while a few had double axis. vas mRNA, one of the markers of PGCs, also kept the expressions in both donor and recipient blastomeres in transplantation of the entire blastoderm. Donor PGCs were frequently detected at germinal anlagen in histological sections of 6-day larvae developed from transplantations of lower and entire blastoderm, but seldom in those of the upper part. These results might suggest that graft transplantation was effective for production of germ-line chimera, but sometimes caused un-regulaory differentiation of graft cells under the community effect.
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  • TAKASHI SUZUKI, HAJIME NAGANO, TORU KOBAYASHI, KOUICHI UENO
    2005 Volume 71 Issue 1 Pages 10-15
    Published: 2005
    Released on J-STAGE: June 08, 2005
    JOURNAL FREE ACCESS
      We investigated species composition, distribution and seasonal changes in the number of larvae and juveniles of crucian carps in the reed zone of Lake Biwa using RAPD markers. A total of 973 larvae and juveniles were collected from the reed zone in a total of nine samplings conducted from April to July, 2002. In the first sampling, 868 larvae and juveniles, mainly preflexion larvae, were collected, and it was found that Gengoroubuna and Ginbuna are distributed within the reed zone. However, Nigorobuna distributed between the center and close to the shore within the reed zone. After the first sampling, larvae and juveniles, mainly postflexion larvae, were collected close to the shore in the reed zone, and most of those were Nigorobuna.
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  • TOSHIHIRO WATANABE
    2005 Volume 71 Issue 1 Pages 16-23
    Published: 2005
    Released on J-STAGE: June 08, 2005
    JOURNAL FREE ACCESS
      To investigate size selectivity of lost traps for the red queen crab Chionoecetes japonicus, a comparative fishing experiment was conducted west of the Oki islands in the Sea of Japan, in which commercially-used traps having a mesh size of 150 mm, traps having circular escape vents with a 90,100 and 110 mm inner diameter, and traps having a small mesh size (34 mm) were utilized. A soaking time of approximately six months was used to evaluate the size selectivity when traps were lost. The size selectivity curves of these traps were estimated by the SELECT model using the likelihood of a multinomial distribution from the proportions taken in the experimental traps catch to the total catch of each carapace width class. The 50 percent retention carapace width of commercially-used traps and the selection range (difference from 75% to 25% retention carapace width) were estimated to be 100.8 mm and 3.4 mm, respectively. The majority of the crabs of carapace width smaller than 99 mm escaped from the commercially-used traps. Ghost fishing does not occur for females because most of the females are smaller than 90 mm carapace width. However, the male crabs of carapace width larger than 103 mm would be retained in the commercially-used traps, then isolated from the population.
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  • KOJI SAIURA, TADASHI TOKAI
    2005 Volume 71 Issue 1 Pages 24-32
    Published: 2005
    Released on J-STAGE: June 08, 2005
    JOURNAL FREE ACCESS
      The boat seine fisheries target mainly anchovy larvae, Engraulis japonica, in the western sea area of the Kii Channel. The current codend is made of minnow netting of which the mesh size, 260 kei (the number of twine in the webbing of 50 cm width) is too fine even for anchovy larvae, and therefore enlargement of the mesh size is required. Experimental cone nets made of minnow netting of three mesh sizes (260, 240, 220 kei) were covered with fine mesh net (mesh material is nylon and mesh size is 0.45 mm). Four towings of each mesh size net, making a total of 12, were carried out. Selectivity curves of each towing for anchovy larvae were estimated with an extended SELECT model for analyzing body size (total length) distributions of the sample from the cone net and cover net catch. In case of a small catch without clogging, the l50 values (the length of 50% retention) of 240 and 220 kei mesh size were 10.5-12.5 mm and 11.0-14.3 mm, respectively. However clogging occurred with large catch volume and then the l50 became smaller than 10 mm, which is equivalent to the l50 of 260 kei mesh size. The boat seine fishing gear has a large cylinder-shaped codend of 1.3 m in diameter and 16 m in length. The cylinder-shaped nets were recognized as being superior for maintaining high filtration efficiency, but clogging over the codend meshes is still unknown. To determine an appropriate mesh size for anchovy larvae, the mesh selectivity should be confirmed under real fishing operation of boat seine fisheries.
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  • FUXIANG HU, MICHIRU SHIGA, KOSUKE YOKOTA, DAISUKE SHIODE, TADASHI TOKA ...
    2005 Volume 71 Issue 1 Pages 33-38
    Published: 2005
    Released on J-STAGE: June 08, 2005
    JOURNAL FREE ACCESS
      To develop mitigation measures for reduction in incidental catch of seabirds in tuna longline fisheries, the hook sinking speed in ten types of branch lines used by Japanese tuna longline vessels was investigated. Also, to improve sinking speed of the hook, two new techniques were tested: material of 10 m line close to the hook was altered from polyamide monofilament to fluorocarbon; and a weight of 15-60 gw was added to the hook. The average sinking speed of the hooks from 0 to 10 m in depth varied from 0.16 to 0.23 m/s in the ten types of branch lines. However, assuming the speed of the fishing vessel for casting is 10 knots, no hook of the ten types sank deeper than 10 m within 150 m from stern, that is, the effective area of the bird-scaring streamer (Tori-pole). The sinking speed of the hook with fluorocarbon line was 1.6 times faster than that with polyamide monofilament. The hook with additional weight of 45 gw sank almost two times faster than the conventional one.
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  • HIDEYUKI YAMASHITA
    2005 Volume 71 Issue 1 Pages 39-43
    Published: 2005
    Released on J-STAGE: June 08, 2005
    JOURNAL FREE ACCESS
      This paper investigates the length distribution of red tilefish Branchiostegus japonicus in catch and the fishing grounds of bottom and vertical longline fisheries in the East China Sea. Monthly data of landed red tilefish were taken by category stratified by fish size at the Nagasaki fish market. Information about the fishing grounds of the landing boats was also taken from fishermen. Experimental fishing with the standard gear commercially used by two fisheries was conducted in several fishing areas, in order to investigate the effect of gear and fishing ground on the length distribution. From the results, the Likelihood Ratio (LR) test using frequency of the size categories in catch showed a significant difference (5% significance level) of the frequency between the fisheries. The LR test using data of length distribution from the experimental catch rejected the effect of the fishing gear (5%). On the other hand, according to the information from the fishermen, two longline fisheries usually covered different fishing areas, and the LR test using data of length distribution by areas supported the effect of the area (5%). The difference of operating area is likely to be the main cause of the length distributions.
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  • TAKANORI MIZUTANI, YASUSHI HARADA, HIDEYUKI YAMASHITA, KEISUKE YAMAMOT ...
    2005 Volume 71 Issue 1 Pages 44-53
    Published: 2005
    Released on J-STAGE: June 08, 2005
    JOURNAL FREE ACCESS
      Diel variability in the catch composition of a bottom trawl survey in the East China Sea is analyzed using the results of sixteen (eight in the day and eight at night) operations. Of several fishes including the Japanese common flying squid, the average catch weight and number were larger at night. Of several fishes including swordtip squid and yellow sea bream, they were larger during the day. A small difference in average size between day and night was observed in Thamnaconus hypargyreus, Japanese horse mackerel, and male and female of Ovalipes punctatus. The average number of species caught was larger at night. It is also suggested that, by operating in both day and night, the number of species appearing in the survey catch can be increased without increasing the number of operations.
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  • IN-OK KIM, TAE-HYUN JO, CHANG-DOO PARK, TADASHI TOKAI
    2005 Volume 71 Issue 1 Pages 54-59
    Published: 2005
    Released on J-STAGE: June 08, 2005
    JOURNAL FREE ACCESS
      This paper presents size selectivity of dredge bagnet for a clam, equilateral Venus Gomphina melanaegis using cover-net fishing experiments with test bagnets of four mesh sizes; 24, 30, 41, 47 mm and covernet of 13 mm mesh size. In the master curve analysis process, master curve equation of mesh selectivity for the clam was estimated to be r(R)=1/[1+exp (-8.63R+5.13)], where R is the ratio of shell length to mesh size. Also, size selectivity was estimated, of a sieve with grid of 12.5 mm bar spacing currently used on the fishing boat deck by fishermen to sort larger size clams from smaller ones of no commercial value. Shell width of the 50 percent retention was 12.7 mm, close to 12.5 mm bar spacing of the grid. This means that the size selectivity of the on-deck sieve was a kind of contact selection. Bar spacing of the grid should be enlarged to retain the clams of commercial size over 35 mm shell length on the on-deck sieve. Enlargement in mesh size of bagnet and other methods to avoid catching small clams of no commercial value were also discussed.
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  • NAOTO HONDA, KAORU FUJITA
    2005 Volume 71 Issue 1 Pages 60-67
    Published: 2005
    Released on J-STAGE: June 08, 2005
    JOURNAL FREE ACCESS
      Smallmouth bass Micropterus dolomieu is an introduced fish native to North America. This fish has been rapidly spreading its habitat in Japan recently due to illegal introductions. It is necessary to capture smallmouth bass efficiently to conserve the aquatic ecosystems. Field experiments were conducted in Lake Aoki to investigate the time zone during which the smallmouth bass were efficiently captured by gillnets, while reducing the bycatch of native fishes. Motion detectors and acceleration sensors were put on gillnets to record the time when fishes were captured. Motion detectors and acceleration sensors record the motion caused by fishes entangled on the gillnet. Fish capture time for each individual was estimated from these time-series data. Eighty-six percent of the smallmouth bass were captured from sunrise to sunset. On the other hand, 91 percent of the crucian carp Carassius sp. and 92 percent of the common carp Cyprinus carpio were captured from sunrise to sunset. It is possible to reduce the bycatch of fish such as crucian carp and common carp by soaking the gillnet in the daytime.
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  • TATSUHITO YOSHIOKA, NOZOMU OGINOME, NAOYUKI UCHIDA
    2005 Volume 71 Issue 1 Pages 68-73
    Published: 2005
    Released on J-STAGE: June 08, 2005
    JOURNAL FREE ACCESS
      The sliced fushi manufactured from the raw materials caught by pole and line (SK-PL) and purse seine (SK-PS) were examined in terms of yield of powder in the manufacturing process, bulk, pressure-resistant strength, and inosine 5′-monophosphate (IMP) content, and the muscle tissues of both katsuobushi were also analyzed histochemically using eosin-Y staining.
      In comparison with SK-PS, SK-PL yielded a significantly lower percentage of the powder (p<0.05), and possessed a significantly higher value (p<0.05) in the bulk, the pressure-resistant strength, and the IMP content, indicating that SK-PL had clearly higher quality than SK-PS.
      Histochemical analysis revealed that the ratio of eosin-Y positive components (EPC) remaining in muscle cells of SK-PL was higher than that of SK-PS. We also found that the EPC-existing situation index (ASPC) estimated from the quantity and the quality of EPC in muscle cells was closely correlated with the yield of powder, the bulk, and the IMP content of the sliced fushi.
      These results suggested that the ASPC was a suitable index to judge the quality of katsuobushi, and a useful tool for studying the development of the manufacturing process to produce a high quality katsuobushi from the raw materials caught by purse seine.
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  • TUGIYO YUKINO, MASAHIRO HAYASHI, YOSHIKAZU INOUE, JUNKO IMAMURA, NAOKI ...
    2005 Volume 71 Issue 1 Pages 74-79
    Published: 2005
    Released on J-STAGE: June 08, 2005
    JOURNAL FREE ACCESS
      Nutritional fortification of Spirulina with docosahexaenoic acid (DHA) was attempted. Fish oil, DHA-ethyl and free DHA were supplemented into the culture of Spirulina as a source of DHA. Exogenous DHA in triglycerides and ethyl ester were not taken up into Spirulina cells. However, the cells took up the DHA in free form from the culture media. The cells without supplementation with DHA did not contain DHA in the cellular fatty acids. The DHA content of the cells was greatly increased by supplementation with DHA into the culture media. It reached to 70.2% of the total fatty acid in the cells.
      DHA was mainly incorporated into the neutral lipids such as monoglycerides and diglycerides in the cells. Free fatty acids were slightly detected in the DHA-fortified cells. A small amount of DHA was also incorporated into glycolipid and phospholipid fractions. Sulfoquinovosyldiacylglycerol in the DHA-fortified Spirulina contained 9.1% of DHA in the total fatty acid. However, only 1-2% of DHA were incorporated into the other polar lipids.
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