NIPPON SUISAN GAKKAISHI
Online ISSN : 1349-998X
Print ISSN : 0021-5392
ISSN-L : 0021-5392
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Volume 72, Issue 5
Displaying 1-37 of 37 articles from this issue
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  • Stock size fluctuations and recruitment characteristics of Japanese flounder Paralichthys olivaceus in the coastal waters off Iwate Prefecture Pacific coast of northern Honshu, Japan
    TOMOAKI GOTO
    2006 Volume 72 Issue 5 Pages 839-849
    Published: 2006
    Released on J-STAGE: September 22, 2006
    DOIhttps://doi.org/10.2331/suisan.72.839
    JOURNAL FREE ACCESS
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      Stock sizes of wild and hatchery-reared flounder Paralichthys olivaceus in the coastal waters off Iwate Prefecture, Pacific coast of northern Honshu, Japan were estimated using VPA from 1990 to 2004. Biomass of wild stock fluctuated between 65 tons and 252 tons, with a continuous increase up to 200 tons from 1994 to 1997 and a continuous decrease after 2002. Biomass of hatchery-reared stock fluctuated between 8 tons and 63 tons, and the current level remained relatively low although a large number of hatchery-reared fishes over a million individuals have been released annually since 2001. The survival rate of hatchery-reared fish might be related to the released number because a negative correlation was represented between them. In wild fish, recruits increased in 1996, 1999 and 2000, but recently decreased to the lowest level. In the present waters, the recruits might be influenced by the coastal water temperature dominated by Tsugaru Warm Current during the pelagic larval period because its level was significantly correlated to spawning success (RPS), that was significantly correlated to the water temperature at 50 m depth in the most coastal region off northern Iwate in July.
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  • Evaluation of VPA estimates of population size of brown sole Pleuronectes herzensteini in northern Hokkaido, Japan
    KAZUTAKA SHIMODA, MIZUE MUROOKA, KAZUHIKO ITAYA, NOBORU HOSHINO
    2006 Volume 72 Issue 5 Pages 850-859
    Published: 2006
    Released on J-STAGE: September 22, 2006
    DOIhttps://doi.org/10.2331/suisan.72.850
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      Evaluation of population size estimates from VPA (back calculation), VPA (forward calculation) and ADAPT VPA of brown sole Pleuronectes herzensteini population in northern Hokkaido, Japan were investigated by retrospective analysis. Relative error between population size by VPA based on eight years of fishing data and estimated population size by three methods of VPA based on one year of fishing data were -54~+109% in VPA (back calculation), -41~+59% in VPA (forward calculation) and -53~+54% in ADAPT VPA. Relative error of age one by VPA (forward calculation) was the lowest of the three methods. At age three to six, relative error by VPA (back calculation) and ADAPT VPA were lower than that of VPA (forward calculation). Relative error of age two and seven showed no different between the methods. We tried to calculate the population size of age one to two by VPA (forward calculation) and over age three by VPA (back calculation). Relative error by the new method was -26~+5%.
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  • Population dynamics of a dragonet Repomucenus valenciennei in Ise Bay, central Japan
    TERUYOSHI NARITA, MONTHON GANMANEE, HIDEO SEKIGUCHI
    2006 Volume 72 Issue 5 Pages 860-872
    Published: 2006
    Released on J-STAGE: September 22, 2006
    DOIhttps://doi.org/10.2331/suisan.72.860
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      Based on long-term observation data (from April 1993 to December 2002) on megabenthos in Ise Bay, central Japan, seasonal and interannual variations in abundance, biomass and spatio-temporal distributions were examined for the dragonet Repomucenus valenciennei dominating in the bay. Then, to examine when and where their recruits are located within the bay, recruits were collected using small-size trawl nets from May 2000 to December 2002. The abundance and biomass of the dragonet decreased in summer when oxygen-poor water developed in the bay, and increased from autumn to next spring when the oxygen-poor water disappeared. Recruits were mainly located in the innermost part of the bay in spring to winter, particularly in winter. According to the cohort separation based on body length histograms, the decrease of the dragonet abundance in summer was induced by avoiding the oxygen-poor water or by high mortality due to the oxygen-poor water. On the other hand, the increase of the dragonet abundance from autumn to next spring was due to recruitment.
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  • Broodstock management and egg collection from reared wild-broodstock of Japanese flounder Paralichthys olivaceus fed commercial extruded pellets
    YASUSHI HONDO, NAOTO MURAKAMI, KEIICHI MUSHIAKE, TATSUO TSUZAKI
    2006 Volume 72 Issue 5 Pages 873-879
    Published: 2006
    Released on J-STAGE: September 22, 2006
    DOIhttps://doi.org/10.2331/suisan.72.873
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      Wild Japanese flounder Paralichthys olivaceus, captured by set-net fishery and reared on raw fish for about 2 years, were divided into two groups. One was fed frozen raw fish (RF group) and the other was fed commercial formula feed (FF group) in each tank for 8 months and 20 months in 2002 and 2003, respectively, before egg collection at the Miyazu Station of the National Center for Stock Enhancement. Broodstock in each group were induced by manipulations of both water temperature and photoperiod conditions to accelerate the maturation, and eggs were collected from each broodstock by induced spawning. Parameters of the FF group such as total number of eggs, fertilization rate, hatching rate, and survival rate of the larvae were compared with those of the RF group. The spawning results from the FF group in both years was slightly inferior to those from the RF group, but the activity, growth and survival rate of the larvae were almost the same. These results indicated that FF was efficacious for broodstock management of Japanese flounder and their egg collection.
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  • Overwintering habitat and low-temperature tolerance of the young mudskipper Boleophthalmus pectinirostris
    TAKESHI TAKEGAKI, TAKAHIRO FUJII, ATSUSHI ISHIMATSU
    2006 Volume 72 Issue 5 Pages 880-885
    Published: 2006
    Released on J-STAGE: September 22, 2006
    DOIhttps://doi.org/10.2331/suisan.72.880
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      The effect of low temperature on size-dependent overwinter mortality in the young (mainly age 0 and 1 year) mudskipper Boleophthalmus pectinirostris was examined by field investigation of overwintering habitat and acute cold-tolerance experiments. The young mudskipper were found from 5.0-55.0 cm in mud depth at Rokkaku River, Saga Prefecture and 4.5-39.0 cm at Tojin River, Kumamoto Prefecture. There was no significant correlation between body size and overwintering depth, showing that young mudskippers use shallow-mud habitats where the temperature sometimes declines to the lethal level, irrespective of size. In the cold-tolerance experiments (3°C, 5°C and 7°C), the fish died earlier under lower temperature condition but no size difference of mortality rate was detected under all temperature conditions. Thus, the size difference of overwinter mortality is probably not due to overwintering depth and acute cold tolerance.
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  • Predation of stocked hatchery-reared juveniles of ocellate puffer Takifugu rubripes in salt pond mesocosm
    DAISUKE SHIMIZU, KAZUTAKA SAKIYAMA, YOH-ICHI TAKAHASHI
    2006 Volume 72 Issue 5 Pages 886-893
    Published: 2006
    Released on J-STAGE: September 22, 2006
    DOIhttps://doi.org/10.2331/suisan.72.886
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      To investigate the effect of predation on the post-release mortality of hatchery-reared juveniles of the ocellate puffer Takifugu rubripes, we reared fish in an experimental salt pond (5,300 m2) with or without predators. The pond was divided into halves, one with 30 sea bass, Lateolabrax sp. (30 cm in mean total length), which is an experimental section, the other (control section) with no predators. Three hundred juveniles (mean standard length, 30 mm) were released into each section of the pond. The survival rate of the juveniles decreased remarkably in the presence of the bass, indicating that predation immediately after release is an important mortality factor. The size of the juveniles and the degree of loss of caudal fin at the time of release showed no influence on growth of juveniles after release or on their survival.
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  • Distribution of white-spotted conger eel Conger myriaster and hagfish Eptatretus burgeri in the shallow region of Tokyo Bay
    MAMI HARADA, TADASHI TOKAI, KEIICHI UCHIDA, TAKAMICHI SHIMIZU
    2006 Volume 72 Issue 5 Pages 894-904
    Published: 2006
    Released on J-STAGE: September 22, 2006
    DOIhttps://doi.org/10.2331/suisan.72.894
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      This study describes distributions of white-spotted conger eel Conger myriaster as a main target species and hagfish Eptatretus burgeri as an incidental catch species for eel-tube fishery. In the shallow region of Tokyo Bay, young conger eels of total length smaller than 35 cm, which are called “meso-anago” by fishermen, are caught and released because of their lower commercial value. For conger eel of marketable size, young conger eel and hagfish, daily catch per unit effort (CPUE, catch weight in kg per one tube gear) was obtained from the logbook of an eel-tube fishing boat during the period from 1994 to 2002, and stratified by the rectangles of 2′ latitude by 2′ longitude. The spatial distribution of monthly average value in the daily CPUE was analyzed. Young conger eels entered the eel-tube fishing ground in August and their bycatch started. Conger eels exceeding 35 cm total length began to be landed in November, and then dispersed over the whole fishing ground. While conger eels were distributed in almost the whole shallow region of Tokyo Bay, hagfish was concentrated in an area of over 30 m deep around the Nakanose shallow, the southwest area of the fishing ground, and its distribution seemed to be constrained by the salinity. Some other factors are also discussed.
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  • Genetic population structure of the spear squid Loligo bleekeri based on mitochondrial DNA
    KINGO ITO, TAKASHI YANAGIMOTO, YOKO IWATA, HIROYUKI MUNEHARA, YASUNORI ...
    2006 Volume 72 Issue 5 Pages 905-910
    Published: 2006
    Released on J-STAGE: September 22, 2006
    DOIhttps://doi.org/10.2331/suisan.72.905
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      The sequence of the mitochondrial DNA noncoding region 4 (mtDNA NC4) was analyzed to investigate the genetic population structure of the spear squid Loligo bleekeri using 545 individiduals captured at six sites around Japan. MtDNA NC4 sequences of 506-528 bp were determined. A total of 55 variable nucleotide sites were detected, defining 48 haplotypes. The average haplotype diversity (0.670) and average nucleotide diversity (0.003) indicated a low level of genetic diversity in the spear squid. Analysis of molecular variation (AMOVA) indicated that most of the genetic variation was distributed within populations. The analysis of haplotype frequency distribution and FST values showed no significant difference among the six sampling sites. These data indicate no genetic structuring of spear squid population around Japan.
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  • The mechanism and oxygen gas inhibition of the degradation of trimethylamine-N-oxide in walleye pollack muscle during storage
    MEIKO KIMURA, NORIO TAKEUCHI, HISANORI NOZAWA, TORU MIZUGUCHI, IKUO KI ...
    2006 Volume 72 Issue 5 Pages 911-917
    Published: 2006
    Released on J-STAGE: September 22, 2006
    DOIhttps://doi.org/10.2331/suisan.72.911
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      The inhibitory effect of oxygen gas on the degradation of trimethylamine-N-oxide (TMAO) to dimethylamine (DMA) and formaldehyde in walleye pollack muscle during storage was investigated. At 5°C storage, the formation of DMA in the muscle was markedly inhibited in oxygen gas than in nitrogen gas, air and vacuum. In the case of frozen storage at −5 and −10°C, oxygen gas effectively inhibited DMA formation. At −20°C, oxygen gas also inhibited DMA formation if improved gas supply to muscle tissue was provided. It was found that optimum pH of DMA formation was neutral in walleye pollack muscle during frozen storage at −20°C which was similar to that of TMAOase-like activity mediated by aspolin, but differed greatly from the optimum pH 5.5 in vitro for non-enzymic reaction carried out in a frozen solution containing TMAO, Fe2+ and cysteine.
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  • Influence of killing procedures and storage temperatures on post-mortem changes in the muscle of cultured three-line grunt Parapristipoma trilineatum
    AKIRA OKAMOTO, YUKI HAMADA, KATSUTAKA MIURA, TAKESHI NONAKA, KOICHI KU ...
    2006 Volume 72 Issue 5 Pages 918-923
    Published: 2006
    Released on J-STAGE: September 22, 2006
    DOIhttps://doi.org/10.2331/suisan.72.918
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      In order to evaluate the effect of different killing methods (instant, struggled, temperature shock and spinal cord destruction) and storage temperatures (iced, 5, 10, 15, 20°C) on postmortem changes in the muscle of the cultured three-line grunt, the adenosine triphosphate (ATP), inosine monophosphate (IMP) concentrations, K-value and rigor index were investigated. A primary study on killing procedures showed that the spinal cord destruction method was the best, since the ATP concentrations resulted in a slow decrease and IMP concentrations, K values and rigor index showed slow increases respectively. For the storage temperature study, two fish groups with different culture temperatures, winter and summer, were used. When the changes in ATP, IMP, K-values and rigor index were compared, fish cultured at winter temperatures had relatively slower variations than those cultured at summer temperatures. Regarding the storage temperature tests, the 10°C storage resulted in slower increases in K-values and rigor index. From these results, it can be concluded that the spinal cord destruction method and storage at 10°C, regardless of culture temperature, were the most effective in delaying post-mortem changes of the three-line grunt even 24 h after postmortem.
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