NIPPON SUISAN GAKKAISHI
Online ISSN : 1349-998X
Print ISSN : 0021-5392
ISSN-L : 0021-5392
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Volume 72, Issue 2
Displaying 1-21 of 21 articles from this issue
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  • Catch fluctuations of the brackish water clam Corbicula japonica in Kiso estuaries, central Japan
    TOMOMI MIZUNO, HIDEO SEKIGUCHI
    2006 Volume 72 Issue 2 Pages 153-159
    Published: 2006
    Released on J-STAGE: March 28, 2006
    DOIhttps://doi.org/10.2331/suisan.72.153
    JOURNAL FREE ACCESS
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      Based on monthly catch-effort data of the brackish water clam Corbicula japonica in Kiso estuaries, central Japan, for 7 years from 1996 to 2002, monthly and yearly averaged daily CPUE (kg/boat/day) of the clam was calculated. Then, fluctuations of yearly averaged CPUE of the clam, which was regarded as an index of the annual quantity of recruits, was examined. Daily CPUE of the clam increased from spring to summer and then decreased toward winter, every year, in both the Ibi/Nagara and Kiso Rivers. For the Ibi/Nagara River, annual catch of the clam has tended to decrease recently while this was not the case for stock size and its recruits. This suggests that the recent decrease of annual catch of the clam may be driven by some factors operating not before but after the recruitment. On the other hand, for the Kiso River, annual catch of the clam did not tend to decrease, although its fluctuations were marked. There were high significant relationships between annual catch and yearly averaged daily CPUE (an index of the quantity of recruits) of the clam. This suggests that catch fluctuations of the clam may be driven by annual quantity of recruits.
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  • Effects of temperature and salinity on the growth of four harmful red tide flagellates occurring in Isahaya Bay in Ariake Sound, Japan
    TOSHIFUMI YAMATOGI, MASAO SAKAGUCHI, MITSUNORI IWATAKI, KAZUMI MATSUOK ...
    2006 Volume 72 Issue 2 Pages 160-168
    Published: 2006
    Released on J-STAGE: March 28, 2006
    DOIhttps://doi.org/10.2331/suisan.72.160
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      Three harmful red tide causative raphidophytes Chattonella antiqua (Hada) Ono, Chattonella marina (Subrahmanyan) Hara et Chihara and Heterosigma akashiwo Hada, and a dinoflagellate Cochlodinium polykrikoides Margalef were isolated from Isahaya Bay, Japan in 2003-2004. The growth characteristics of these four clonal cultures were examined in 60 different combinations of temperature (10-32.5°C) and salinity (16-36) under a light intensity of 80 μmol/m2/s. C. antiqua reproduced at 15-32.5°C and 16-36 PSU, and the maximum growth rate was 0.99 day-1 at 30°C and 32 PSU. C. marina reproduced at 12.5-32.5°C and 16-36 PSU. The maximum growth rate was 0.83 day-1, which was obtained at 30°C and 24 PSU. H. akashiwo reproduced at 10-32.5°C and 16-36 PSU. The maximum growth rate was 1.14 day-1 at 25°C and 24 PSU. C. polykrikoides reproduced at 10-32.5°C and 16-36 PSU. The maximum growth rate was 0.56 day-1 at 27.5°C and 32 PSU. Four red tide flagellates examined in this study appeared to be euryhaline. The optimum temperatures for maximum growth were different in each species and these conditions clearly corresponded with recent red tide occurrences in Isahaya Bay. Compared with growth conditions previously reported, four isolates from Isahaya Bay are likely to tolerate relatively higher temperature.
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  • Ontogenetic changes in tolerance for environmental stress in Japanese flounder Paralichthys olivaceus during early development
    YUKINORI SHIMADA, TAKAHITO SHIKANO, TADAHISA SEIKAI
    2006 Volume 72 Issue 2 Pages 169-173
    Published: 2006
    Released on J-STAGE: March 28, 2006
    DOIhttps://doi.org/10.2331/suisan.72.169
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      Ontogenetic changes in physiological tolerance during larval development of Japanese flounder Paralichthys olivaceus were examined relative to a variety of environmental stresses as follows: freshwater, high salinity (salinity range: 30-55), high water temperature (temperature range: 20-36°C) and formalin (concentration range: 0-0.6%). Highest stress tolerance was shown by newly hatched larvae (1 day after hatching), and then decreased drastically until 10 days after hatching. We considered that the high sensitivity to external environmental stresses at 10 days after hatching was caused by the development of the mouth and opercula. Patterns of tolerance change during the early life stages differed depending on the environmental stresses.
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  • Mesh selectivity of gillnet for pointhead flounder Cleisthenes pinetorum
    KEN-ICHI WAKAYAMA, YASUZUMI FUJIMORI, KAZUHIKO ITAYA, OSAMU MURAKAMI, ...
    2006 Volume 72 Issue 2 Pages 174-181
    Published: 2006
    Released on J-STAGE: March 28, 2006
    DOIhttps://doi.org/10.2331/suisan.72.174
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      Fishing experiments were carried out in Ishikari Bay, Hokkaido using a bottom gillnet with eight different mesh sizes to estimate the mesh selectivity for pointhead flounder Cleisthenes pinetorum. A total of 957 pointhead flounder were caught. The SELECT analysis with maximum likelihood method was used to fit the different functional models, the normal, lognormal, and bi-normal model. The catch data except for entangling catch was used for calculation. The bi-normal model was found to fit the data best. For the selectivity curve on the bi-normal model, the relative length (the ratio of fish length to mesh size) with the maximum efficiency was obtained as 1.87.
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  • Influence of water temperature and rearing density on thymus development of cultured ayu Plecoglossus altivelis altivelis, and relation between the thymus volume
    HIDEO HARA, MICHITAKA YAMAMOTO, SEIICHI MURAKI, SATOSHI MIWA
    2006 Volume 72 Issue 2 Pages 182-185
    Published: 2006
    Released on J-STAGE: March 28, 2006
    DOIhttps://doi.org/10.2331/suisan.72.182
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      We investigated the effects of water temperature and rearing density on the development of the thymus in juvenile ayu Plecoglossus altivelis altivelis from three different origins, Shiga, Toyama and Kanagawa. The thymus volume of the ayu that had been reared at high water temperature (about 20°C) was significantly smaller than that of the ayu reared at low water temperature (about 15°C). Rearing density ranging from 0.58 to 10.95 kg/m3 water at the end of the experiment did not affect the thymus development.
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  • Advanced spawning of yellowtail Seriola quinqueradiata as early as December by manipulations of both photoperiod and water temperature
    KAZUHISA HAMADA, KEIICHI MUSHIAKE
    2006 Volume 72 Issue 2 Pages 186-192
    Published: 2006
    Released on J-STAGE: March 28, 2006
    DOIhttps://doi.org/10.2331/suisan.72.186
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      The present study examined the combined effects of photoperiod and temperature control on the ovarian maturation and human chorionic gonadotropin (HCG)-induced spawning of yellowtail Seriola quinqueradiata, with the aim of achieving advanced spawning as early as December. In experiments conducted from 2002 to 2004, the daylength was set to 8 hours (8L16D) for 10 days followed by a 10-hour daylength extension to 18 hours (18L6D) for the next 80 days under controlled water temperature that was maintained at 19°C before the injection of HCG. Female broodstock kept under these controlled conditions were induced to mature more rapidly than those kept under natural conditions. Neither controlled photoperiod nor controlled water temperature was sufficient to induce the maturation of fish. During these 3 years, fish kept under both controlled conditions were able to spawn in advance during December, with the total eggs produced per female ranging from 87×103 to 1000×103. Survival rates for the first 10 days of the rearing experiments of larvae at first spawning obtained in 2002 and 2004 were 14.1 and 36.7%, respectively. These values were similar to those obtained during the spawning season in April. This experiment showed that manipulations of both photoperiod and water temperature are effective in accelerating the maturation of female yellowtail broodstock and that good quality eggs may be obtained as early as December after HCG injection.
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  • Growth kinetics and paralytic shellfish poisoning toxin production in phosphorus-limited cultures of Alexandrium catenella
    ATSUSHI MATSUDA, TOSHITAKA NISHIJIMA, KIMIO FUKAMI, MASAO ADACHI
    2006 Volume 72 Issue 2 Pages 193-200
    Published: 2006
    Released on J-STAGE: March 28, 2006
    DOIhttps://doi.org/10.2331/suisan.72.193
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      The effects of phosphorus deficiency on the growth and PSP toxin production by an axenic clone culture of Alexandrium catenella TNY7 were examined under semi-continuous culture conditions.
       The specific growth rate (μ) diminished with decreasing cell quota for phosphorus (QP). The relationship between μ and QP was described by the Droop equation. The calculated maximum specific growth rate and minimum cell quota for phosphorus were 0.79day-1 and 0.28 pmol/cell, respectively. Toxin content per cell increased with decreasing specific growth rate. When phosphorus limitation in the cells was the most severe, the highest toxin content per cell (92.3 fmol/cell) was obtained. The highest toxin content per cell was approximately 4 to 6 times higher than in nutrient sufficient conditions and 22 times higher than in nitrogen deficient conditions. Toxin composition and ratio remained constant independent of specific growth rate and phosphorus limitation in the cells.
       Phosphorus limitation is one of the most important environmental factors which increase the total toxin per cell of A. catenella. Phosphorus limited cells of A. catenella may have some effect on increase in toxin content of shellfish in natural waters.
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  • Fishing efficiency estimated based on the abundance from virtual population analysis and bottom-trawl surveys of Pacific cod Gadus macrocephalus in the waters off the Pacific coast of northern Honshu, Japan
    YUJI UEDA, YOJI NARIMATSU, TSUTOMU HATTORI, MASAKI ITO, DAIJI KITAGAWA ...
    2006 Volume 72 Issue 2 Pages 201-209
    Published: 2006
    Released on J-STAGE: March 28, 2006
    DOIhttps://doi.org/10.2331/suisan.72.201
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      Fishing efficiency is one of the most important parameters to estimate population size using the swept area method based on bottom-trawl surveys. In the present study, the fishing efficiency of the stock of Pacific cod Gadus macrocephalus in the waters off the Pacific coast of northern Honshu, Japan was estimated based on the abundance obtained from virtual population analysis. Fishing efficiencies were estimated to fit the population size obtained from the swept area method to that obtained from virtual population analysis. Fishing efficiency was estimated as 0.54 for 1-year-old and 0.12 for 2-year-old fish, which had a significant difference. This is because, the fishing efficiency of 2-year-old fish was mainly affected by encounter rate to fishing gear caused by the difference of distribution area among the fish of different ages; many of the 2-year-old and over fish distributed on un-trawlable parts, e.g. rough-bottomed reefs.
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  • Reproductive biology of the grenadier Coelorinchus jordani (Gadiformes, Macrouridae) in Kagoshima Bay, southern Japan
    JUN OHTOMI, RYUICHI SAKATA
    2006 Volume 72 Issue 2 Pages 210-216
    Published: 2006
    Released on J-STAGE: March 28, 2006
    DOIhttps://doi.org/10.2331/suisan.72.210
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      Population biological aspects of the macrourid fishes (Gadiformes) have not been sufficiently examined yet. The reproductive biology of the grenadier Coelorinchus jordani (Macrouridae) was studied using a large number of specimens which were collected in Kagoshima Bay, at 115-227 m in depth, by a commercial bottom trawler. Ovarian maturity stages were divided into three categories based on macroscopic visual examination of ovaries: stage I (undeveloped: oocytes invisible), stage II (early ripe: oocytes visible but not hydrated) and stage III (ripe: presence of hydrated oocytes). The size at sexual maturity of females was estimated to be 35 mm in pre-anal length. In the present study, females with stage-III ovaries which contained the hydrated oocytes were defined as mature females. Based on the seasonal changes in the gonado-somatic index and occurrence of the mature females, the spawning season of C. jordani was estimated to continue almost all year round with its minor peaks in spring and autumn. Percentage occurrence of mature females tended to be higher in the shallow area (less than 200 m in depth) than the deep area (above 200 m in depth) in the bay.
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  • Population structure, condition factor and relative growth of the grenadier Coelorinchus jordani (Gadiformes, Macrouridae) in Kagoshima Bay, southern Japan
    JUN OHTOMI
    2006 Volume 72 Issue 2 Pages 217-222
    Published: 2006
    Released on J-STAGE: March 28, 2006
    DOIhttps://doi.org/10.2331/suisan.72.217
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      In order to examine the sex ratio, body size composition, condition factor and relative growth, a total of 1638 specimens of the grenadier Coelorinchus jordani (Gadiformes, Macrouridae) was collected from Kagoshima Bay, southern Japan, at 115-227 m in depth, using a commercial bottom trawler. Proportions of males and females were not significantly different in the shallow area (less than 200 m in depth), while in the deep area (above 200 m in depth), males had a significantly higher proportion than females. C. jordani had a sexual dimorphism in body size. The body size was significantly greater in the shallow area than the deep area for both sexes. Small individuals less than 20 mm in pre-anal length occurred only in the deep area. The condition factors of both males and females changed with seasonal oscillation. The symmetric relationship between pre-anal length and total length was represented by significantly different equations between sexes. The relationship between pre-anal length and body weight was described by a double-logarithmic linear equation without significant difference between sexes.
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  • Effects of ripening temperature on the chemical and microbiological characteristics of salmon Izushi
    MASANORI SASAKI, YUJI KAWAI, MAMORU YOSHIMIZU, HARUO SHINANO
    2006 Volume 72 Issue 2 Pages 223-230
    Published: 2006
    Released on J-STAGE: March 28, 2006
    DOIhttps://doi.org/10.2331/suisan.72.223
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      The effects of ripening temperature on the chemical and microbiological characteristics of Izushi made of chum salmon (Oncorhynchus keta) were investigated. Izushi were ripened for a cumulative temperature 280°C•d at 5, 10, 15 and 20°C. When ripened at higher temperatures, total acid, volatile basic nitrogen, free amino acid, aerobic bacteria, and lactic acid bacteria obviously increased in Izushi products, and pH values and yields of the products were reduced. For lactic acid bacteria, Leuconostoc mesenteroides was dominant in the Izushi at every ripening temperature. In the Izushi ripened at 5°C, Saccharomyces cerevisiae was dominant for yeast, whereas yeast was not detected in that ripened at 10, 15 and 20°C. In sensory evaluation, Izushi ripened at higher temperatures were not so acceptable as those ripened at at lower temperatures. These results suggested that high-quality salmon Izushi might be produced by ripening at lower temperature for a long period.
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  • Effect of inoculation with starter cultures of yeast and lactic acid bacterium on the chemical and microbiological characteristics of salmon Izushi
    MASANORI SASAKI, YUJI KAWAI, MAMORU YOSHIMIZU, HARUO SHINANO
    2006 Volume 72 Issue 2 Pages 231-238
    Published: 2006
    Released on J-STAGE: March 28, 2006
    DOIhttps://doi.org/10.2331/suisan.72.231
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      Two microbial strains of yeast Saccharomyces cerevisiae IZS-Sc1 and lactic acid bacterium Leuconostoc mesenteroides subsp. cremoris IZS-Lmc1 were inoculated into salmon Izushi as starter cultures for ripening. The strains had previously been isolated from ripened Izushi at 5°C. After Izushi had been ripened for a cumulative temperature of 280°C•d at 5, 10, 15 and 20°C, investigation of chemical and microbiological characteristics and organoleptic observations were carried out for the ripened Izushi. Inoculation of starter cultures accelerated ripening of Izushi. In the 5°C-ripened Izushi, the inoculated species were dominant, occupying 93-100%, and an organoleptically higher evaluation was obtained. For the Izushi ripened at 10, 15 and 20°C, yeast was not detected as well as in those without inocula and a tendency toward excessive ripening was observed. The Effect of ripening temperature on the characteristics of Izushi samples inoculated with starter cultures was closely similar to the effect on those without inocula.
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