NIPPON SUISAN GAKKAISHI
Online ISSN : 1349-998X
Print ISSN : 0021-5392
ISSN-L : 0021-5392
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Volume 76, Issue 3
Displaying 1-46 of 46 articles from this issue
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Obituary
Prize Winners of the Japanese Society of Fisheries Science Awards 2009
Scientific Achievement Award in Fisheries Science 2009
Originals
  • Review of bycatch mitigation measures in tuna longline fishery
    MASASHI KIYOTA, KOSUKE YOKOTA
    2010 Volume 76 Issue 3 Pages 348-361
    Published: 2010
    Released on J-STAGE: July 07, 2010
    DOIhttps://doi.org/10.2331/suisan.76.348
    JOURNAL FREE ACCESS
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      This review classifies and explains the bycatch mitigation measures in tuna longline fishery based on their functional mechanism across bycatch species. In longline fishery bycatch mortality occurs through a common process that typically follows these stages: 1) fishing operations overlap with the distribution of non-target animals; 2) non-target animals perceive the baited hook (or hooked fish) as food and approach it; 3) contact with the fishing gear; 4) become hooked or entangled; and 5) die. Mitigation measures block one or several stages of this process to reduce the bycatch and resultant mortality by avoiding the spatio-temporal overlap (time and area closure, and modification of gear configuration and operational pattern), by diminishing perception and attraction of baited hooks (night setting, offal control, and blue-dyed bait), by interrupting the physical contact between non-target animals and fishing gear (bird-scaring line, line weighting, underwater and side setting, and deterrent methods using aversive stimuli), by preventing hooking (hook and bait modification), and by reducing post-hooking mortality (safe release with rescue devices). Since there is no panacea for every occasion, combined use of complementary methods that fit the actual situation of fishing operation enhances the effectiveness of mitigation. The experience and innovation of fishermen are important in developing and improving the mitigation measures.
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  • Acoustic biomass estimate of California headlightfish Diaphus theta, off eastern Hokkaido, Japan
    HIROKI YASUMA, TATSUKI OHSHIMA, SATOSHI HONDA, KAZUSHI MIYASHITA, ICHI ...
    2010 Volume 76 Issue 3 Pages 362-369
    Published: 2010
    Released on J-STAGE: July 07, 2010
    DOIhttps://doi.org/10.2331/suisan.76.362
    JOURNAL FREE ACCESS
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      California headlightfish Diaphus theta is the most abundant mesopelagic fish in the subarctic Pacific. Day- and nighttime field acoustic data and biological samples were obtained in January 2000, in the Pacific area off eastern Hokkaido to estimate fish density and total biomass of D. theta. Sound scattering layers composed mainly of immature D. theta (63 mm length on average) were widely distributed around the shelf edge (>300 m water depth). Relatively dense schools were observed below the depth of 250 m during the daytime, although the schools were scattered widely above 50 m depth during the nighttime. Fish density was estimated to be 17.3 g/m2 on average, which was more than several times higher than that estimated by conventional methods such as net sampling gears. Total biomass in the survey area (2,083 km2) was estimated to be about 35,900 t.
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  • Egg eyeing rates and physical characteristics of spawning redds of stocked amago salmon Oncorhynchus masou ishikawae in a stream
    TETSUYA TOKUHARA, DAISUKE KISHI, TORU HARA, HIROSHI KUMAZAKI
    2010 Volume 76 Issue 3 Pages 370-374
    Published: 2010
    Released on J-STAGE: July 07, 2010
    DOIhttps://doi.org/10.2331/suisan.76.370
    JOURNAL FREE ACCESS
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      We released mature male and female amago salmon Oncorhynchus masou ishikawae reared in a hatchery into a small stream in central Japan and surveyed the location of spawning sites, water depth, current velocity, substrate size and the egg eyeing rates in the redds in 2007.
       The redds were observed only at the pool ends and in riffles. The average water depth was 20.5±9.0 cm (Mean±SD). Averages of surface and bottom velocity were 22.7±9.1 cm/sec and 16.1±10.7 cm/sec, respectively. Preferred substrate size was fine pebbles of 16-32 mm. The average egg eyeing rate in the redds was calculated to be 90.6%. As a result, physical characteristics of redds and egg eyeing rates observed in our study were similar to the values of wild fish reported in previous studies.
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  • Effects of nutrient deprivation on photosynthetic pigments and ultrastructure of chloroplasts in Porphyra yezoensis
    CHIKA UEKI, AKIO MURAKAMI, TOSHIAKI KATOH, NAOTSUNE SAGA, TAIZO MOTOMU ...
    2010 Volume 76 Issue 3 Pages 375-382
    Published: 2010
    Released on J-STAGE: July 07, 2010
    DOIhttps://doi.org/10.2331/suisan.76.375
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      To understand the “chlorosis” in the thalli of Porphyra yezoensis, we examined the reduction of photosynthetic pigments and the changes in ultrastructures of cells and organelles. In two-week culture in the media without N, P or Fe, all thalli gradually discolored. Photosynthetic pigments (chlorophyll a, phycoerythrin and phycocyanin) extensively reduced, though the degree and the pattern of the reduction varied according to deprived nutrients. While the chloroplasts shrank due to the nutrient deprivation, the vacuoles swelled and the starch grains accumulated in cytoplasm.
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  • Estimating the spawning escapement of pink salmon Oncorhynchus gorbuscha using the area-under-the-curve method in the Rusha River of the Shiretoko Peninsula, Hokkaido Island
    YUYA YOKOYAMA, YOSUKE KOSHINO, KOTA MIYAMOTO, HIDEAKI KUDO, SHUICHI KI ...
    2010 Volume 76 Issue 3 Pages 383-391
    Published: 2010
    Released on J-STAGE: July 07, 2010
    DOIhttps://doi.org/10.2331/suisan.76.383
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      Pacific salmon Oncorhynchus spp. plays a role in sustaining the biodiversity and production of the terrestrial ecosystem. Accurate estimation of the escapement and spawning dynamics is important for the quantifying the effect of salmon on the riparian ecosystem. The objective of this paper is to estimate accurately the escapement and spawning dynamics of wild pink salmon O. gorbuscha at the Rusha River in the Shiretoko World Natural Heritage area in 2006-2008. The escapement of pink salmon was estimated by the area-under-the-curve method (AUC) with the standard error based on the bootstrap method. The estimated escapement indicated appropriate results. The carrying capacity of spawning redds, however, was far lower than escapements in the available spawning area.
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  • Effects of temperature and NaCl content on production of taste-active components in heshiko during the aging process of salted mackerel with rice bran
    YASUYUKI KOSAKA, YUKA KINOSHITA, TOORU OOIZUMI, YOSHIAKI AKAHANE
    2010 Volume 76 Issue 3 Pages 392-398
    Published: 2010
    Released on J-STAGE: July 07, 2010
    DOIhttps://doi.org/10.2331/suisan.76.392
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      Effects of temperature and NaCl content on changes in viable count as well as production of taste-active components, lactic acid (LA), free amino acids (FAA), and acid soluble peptides (ASP) in the flesh portion of heshiko were investigated through the aging process of salted mackerel with rice bran. The viable count in GYP agar plate containing 2.5 or 10.0% NaCl under either the aerobic or anaerobic cultivation condition gradually increased with aging period irrespective of the temperature. The elevation of the aging temperature from 10°C to 30°C barely affected the changes of viable count and slightly increased the production of LA, while the production of FAA and ASP was promoted depending on the temperature during the aging process. On the other hand, the reduction of the amount of NaCl added remarkably increased the viable count and the production of LA depending on the actual NaCl content in rice bran, while the increases of FAA and ASP were dependent on the NaCl content in the flesh part of heshiko. These results suggested that the production mechanism of FAA and ASP was different from that of LA and was independent of microbial growth during the processing of heshiko.
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