NIPPON SUISAN GAKKAISHI
Online ISSN : 1349-998X
Print ISSN : 0021-5392
ISSN-L : 0021-5392
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Volume 81, Issue 4
Displaying 1-46 of 46 articles from this issue
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Foreword
2014 Awards of Excellence for Science Papers
Achievement Award for Young Scientist in Fisheries Science 2014
Originals
  • Relationship between catch per unit effort and density of Japanese common squid Todarodes pacificus under squid jigging boat
    TAKAFUMI SHIKATA, JUNICHI MOCHIHIRA, YOSHIMI TAKAO, KAZUHIRO SADAYASU, ...
    2015 Volume 81 Issue 4 Pages 659-666
    Published: 2015
    Released on J-STAGE: August 15, 2015
    DOIhttps://doi.org/10.2331/suisan.81.659
    JOURNAL FREE ACCESS
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      Night-time squid jigging operations were conducted by the R/V Hakusan-maru (167 gross tons) equipped with 78 metal halide lamps (234 kW) in the Sea of Japan, and the changes in catch per unit effort (CPUE) and density of Japanese common squid Todarodes pacificus under the boat during operations were investigated. The squid density was measured using a quantitative echosounder. CPUE increased with increasing squid density during operations, but the increase of CPUE slowed down when CPUE was extremely high. The rise in CPUE with increasing squid density greatly differed by operation. The relationship between CPUE and squid density (S) was expressed as CPUE=A・S/(B−1+S), where A is an upper limiting CPUE and B is catchability of the squid. This relationship suggested that CPUE would hardly decrease under considerably high squid density conditions even though the squid density was somewhat decreased by reduced lighting, so additional operations were conducted to test this prediction. The squid density was increased by reducing the number of lit lamps in the middle of operation and CPUE was often increased. These results indicate that reduced lighting is effective to save energy (fuel) without reducing squid catch.
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  • Overwintering mortality of juvenile ayu Plecoglossus altivelis altivelis and environmental factors in Lake Biwa
    AKIHISA SAKAI, TAKAHIRO USUKI, YOSHITAKA KATAOKA
    2015 Volume 81 Issue 4 Pages 667-673
    Published: 2015
    Released on J-STAGE: August 15, 2015
    DOIhttps://doi.org/10.2331/suisan.81.667
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      The characteristics of overwinter mortality of juvenile ayu Plecoglossus altivelis altivelis were studied in Lake Biwa in 1999 and 2002-2010. The positive correlation between CPUE of ayu in set nets in February and April was significant except for 2006, when heavy mortality occurred during February to April. In 2006, the water temperature was the lowest in the 10 years, and plankton biomass was at a relatively low level from January to April. The condition of ayu in mid-February 2006 was relatively poor. The heavy mortality during the 2006 winter may have resulted from low-temperature stress and deterioration of nutritional status.
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  • Catch characteristics of bottom and pelagic longline fisheries for ocellate puffer Takifugu rubripes in the western part of the Sea of Japan
    TAKASHI KATAYAMA
    2015 Volume 81 Issue 4 Pages 674-680
    Published: 2015
    Released on J-STAGE: August 15, 2015
    DOIhttps://doi.org/10.2331/suisan.81.674
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      This study investigated the catch characteristics of bottom and pelagic longline fisheries for ocellate puffer Takifugu rubripes using catch data obtained in the western part of the Sea of Japan. The effects of gear type, fishing area and month on CPUE (number caught/100 hooks) and sex ratio (ratio of females) were analyzed by multiple regression analysis and logistic regression analysis, respectively. As a result of the multiple regression analysis for CPUE, the model including gear, area, month and interaction of gear and month as explanatory variables was selected as the best one. The logistic regression analysis for sex ratio found that the model including gear, area, month, interaction of gear and area, and interaction of area and month as explanatory variables was optimal. It is known that CPUE is lower and the size of individuals is bigger for the bottom longline fishery than the pelagic longline fishery. Furthermore, the sex ratio of fish caught depends on the fishing area whereas no such tendency is shown in the pelagic longline fishery. The results of this study confirm the empirical knowledge of previous studies that catch characteristics clearly differ between the two longline fisheries.
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  • Estimation of diets and food sources of juvenile marbled sole in Sengen Bay, Seto Inland Sea, Japan, based on carbon and nitrogen stable isotope ratios
    YASUSHI ITO, TSUKASA YOSHIDA, CHIZURU HARIMA
    2015 Volume 81 Issue 4 Pages 681-687
    Published: 2015
    Released on J-STAGE: August 15, 2015
    DOIhttps://doi.org/10.2331/suisan.81.681
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      A study with carbon and nitrogen stable isotope analysis was conducted for inferring the diets and food sources of juvenile marbled sole Pseudopleuronectes yokohamae. A field investigation was conducted inside Sengen Bay, the Seto Inland Sea, Japan. The bottom of Sengen Bay has a mix of dotted seaweed bed areas and muddy sand bed areas. In both bed types, juveniles with a total length of about 15 mm fed on Harpacticoida, and sedimentary organic matter was the source of the food chain. Juveniles with a total length exceeding 30 mm in the dotted seaweed beds fed on benthic, sessile and phyla animals, whereas the juveniles in the muddy sand areas fed on only benthos. Particulate organic matter was the food source in both areas.
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  • Growth patterns and sex ratios of Conger japonicus and C. erebennus in Tokyo Bay
    SATOSHI KATAYAMA, SEIJI AKIYAMA, YUKIKO SHIMOMURA, HIROAKI KUROGI
    2015 Volume 81 Issue 4 Pages 688-693
    Published: 2015
    Released on J-STAGE: August 15, 2015
    DOIhttps://doi.org/10.2331/suisan.81.688
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      Ages of the eels Conger japonicus (n=189) and C. erebennus (n=448) in Tokyo Bay were determined by otolith sectioning. The estimated age range of C. japonicus specimens was 1+ to 6+ yr (modal range 2+ to 4+ yr), and of C. erebennus 0+ to 11+ yr (modal range 5+ to 8+ yr). Many C. erebennus taken measured over 1000 mm in total length and were more than 6+ yr. C. erebennus is therefore characterized as a large-sized eel in comparison with C. myriaster, for which size, age estimations and growth patterns are well documented. Males of C. japonicus and C. erebennus accounted for 2-6% of the specimens sampled in this study, suggesting that the population in Tokyo Bay is composed predominantly of females.
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  • Estimating the threshold amount of adductor muscle arginine phosphate content required for recovery of vitality in the scallop Mizuhopecten yessoensis
    TADAAKI TAKEDA, IZUMI SAKURAI, KIMIHIKO MAEKAWA, HISANORI NOZAWA
    2015 Volume 81 Issue 4 Pages 694-700
    Published: 2015
    Released on J-STAGE: August 15, 2015
    DOIhttps://doi.org/10.2331/suisan.81.694
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      The Japanese scallop Mizuhopecten yessoensis, which is a major fisheries resource in Japan, is farmed in coastal areas such as Lake Saroma in Hokkaido. Recently, mass die-offs of cultured Japanese scallops have been frequently observed at Lake Saroma. Our previous results suggested that arginine phosphate concentration in the adductor muscle can be a good predictor of scallop die-off. However, when Japanese scallops are reared in a stressful environment such as high water temperature, low salinity, or anoxia and then returned to their normal rearing environment, some individuals have been found to recover, while others die. This study aimed to determine whether arginine phosphate may be an indicator for predicting which individuals recover and which die. The results suggested that the scallops would die without recovering when arginine phosphate levels decreased to approximately 5 μmol/g or lower, even if they were returned to the normal rearing environment.
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  • Effect of giant jellyfish Nemopilema nomurai as supplemental feed on threadsail filefish Stephanolepis cirrhifer
    YUKO MIYAJIMA-TAGA, REIJI MASUDA, AYAKO KURIHARA, YOH YAMASHITA, TOSHI ...
    2015 Volume 81 Issue 4 Pages 701-714
    Published: 2015
    Released on J-STAGE: August 15, 2015
    DOIhttps://doi.org/10.2331/suisan.81.701
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      We conducted a 30-day feeding experiment on threadsail filefish Stephanolepis cirrhifer to evaluate the efficacy of giant jellyfish Nemopilema nomurai on the growth and body composition of the filefish. Four treatments were prepared: starved (control, S), fed only jellyfish (J), fed only pellets (control, P), and fed both jellyfish and pellets (JP). Threadsail filefish consumed the giant jellyfish as much as 5.6 and 4.1 times their own body weight per day in the J and JP treatments, respectively. Fish in the S treatment had 68% mortality, whereas the J treatment had no mortality. Fish in the JP treatments showed significantly faster growth than those in the P treatment. The giant jellyfish contained a high ratio of n-6 highly unsaturated fatty acids, especially arachidonic acid as well as free amino acids, especially taurine. The high contents of these acids reflected those of fish body composition. These results showed that feeding giant jellyfish for threadsail filefish improved their growth and body composition, and we therefore recommend the use of jellyfish as supplemental feed for stock enhancement or aquaculture.
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  • Hatchery-reared Japanese eel Anguilla japonica larvae ingest various organic matter formed as part of marine snow
    TSUTOMU TOMODA, HIROAKI KUROGI, MASANORI OKAUCHI, MASAAKI KAMOSHIDA, H ...
    2015 Volume 81 Issue 4 Pages 715-721
    Published: 2015
    Released on J-STAGE: August 15, 2015
    DOIhttps://doi.org/10.2331/suisan.81.715
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      We observed the feeding incidence of Japanese eel Anguilla japonica larvae of 5-28 days post-hatch (dph) using various organic matter formed as part of marine snow. Food organisms such as microalgae (Rhodomonas sp., Isochrysis galbana, Cyclotella sp., and Chaetoceros calcitrans) and appendicularian Oikopleura dioica were raised as the primary food source of marine snow. In algal feeding trials, 10-28 day-old eel larvae ingested algal cells and transparent exopolymer particles (TEP) produced during the exponential growth phase. Furthermore, the feeding incidence of the larvae showed an increasing trend within the range of 40-100% with larval age (dph) and algal cell concentration. In appendicularian feeding trials, 9-day-old eel larvae ingested a larval tadpole body and abandoned house wreckage. The aforementioned gel-like particles were excreted smoothly out of the end of the mid-hind gut during observation. These results indicate that hatchery-reared Japanese eel larvae ingest organic matter formed as part of marine snow as well as natural eel larvae. The gelatinous substances from microalgae and appendicularian may be available as initial food sources for Japanese eel larvae because of their physical properties (buoyancy, suspensibility, absorption, aggregability, and flexibility) in seawater.
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