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Hokkaido University Collection of Scholarly and Academic Papers (135.521 recursos)

HUSCAP (Hokkaido University Collection of Scholarly and Academic Papers) contains peer-reviewed journal articles, proceedings, educational resources and any kind of scholarly works of Hokkaido University.

????????????? = Bulletin of Fisheries Sciences, Hokkaido University

Mostrando recursos 1 - 20 de 81

  1. 大阪湾における麻痺性貝毒原因渦鞭毛藻Alexandrium tamarenseと珪藻Skeletonema sp.の栄養塩利用性の比較

    夏池, 真史; 山本, 圭吾; 中嶋, 昌紀; 澤山, 茂樹; 今井, 一郎
    Alexandrium tamarense is a toxic dinoflagellate known to cause paralytic shellfish poisoning to human and marine animals. Previous studies observed the depletion of macronutrients during the A.tamarense blooming periods in Osaka Bay, Japan, and suggest the different nutrient availabilities between surface and bottom layers allow A.tamarense to grow. In this study, the field observation and Algal growth potential(AGP) bioassay with A.tamarence and non-toxic, dominant diatom Skeletonema sp. in Osaka Bay are conducted to compare the nutrient availabilities during the period of A.tamarense occurrences in the Bay. The field observations confirmed the depletion of dissolved inorganic nitrogen, PO4-P, and SiO2-Si concentrations...

  2. Different Nutrient Availabilities of Surface and Bottom Water under Nutrient-depleted Conditions during Bloom Formation of the Toxic Dinoflagellate Alexandrium tamarense in Osaka Bay, Japan

    Natsuike, Masafumi; Shiraishi, Tomotaka; Ishii, Ken-Ichiro; Yamamoto, Keigo; Nakajima, Masaki; Sawayama, Shigeki; Imai, Ichiro
    Alexandriium tamarense is a toxic dinoflagellate known to produce neurotoxins cause paralytic shellfish poisoning to human and marine animals. To understand the growth dynamics of A.tamarense, the seasonal changes in A,tamarense vegetative cells and environmental factors were evaluated using monthly field observations at two fixed stations in Osaka Bay, Japan, from January to May 2008. Additionally, a bioassay with axenic A.tamarense clonal cultures was performed to determine the growth potentials and growth-limiting nutrients of seawater samples collected during the field observations. The density of A.tamarense increased from February to April, and depletions of dissolved phosphate and silicate were observed in...

  3. A new approach of determining gillnet selectivity based on the relationship between fish length and girth to estimate the length distribution of fish encountering a net

    Fujimori, Yasuzumi
    A method of estimating the length distribution of fish that encounter a gillnet based on selectivity curve using the length-girth relationship of the target fish was proposed for use in fish surveys. This method was verified in a tank experiment using gillnets for rainbow trout(Oncorhynchus mykiss) of known size composition. Data from on body part of fish caught, near the dorsal fin, were used to estimate the selectivity curve. The curves, expressed as a normal curve, of each mesh size had the same shape, even though each was estimated individually. Additionally, there was a complete linear relationship between the mean...

  4. 海底耕耘を活用したChattonella赤潮制御の試み

    今井, 一郎; 各務, 彰記; 小原, 静夏; 結城, 貴志; 小池, 一彦; 萩原, 悦子; 小川, 憲太; 米山, 弘行
    Diatoms are the most predominant phytoplankton group in the coastal sea and many planktonic diatom species produce resting stage cells in their life cycle to endure unfavorable conditions. These diatom resting stage cells play an important role in initiating the blooms. It is empirically known that diatom cells are sparse in water during the course of red tides of harmful flagellates such as dinoflagellates and raphidophytes. A promising strategy to control the occurrences of red tides by harmful flagellates is to artificially induce diatom blooms just before the development of red tides of harmful flagellates. There usually exist more than...

  5. 海底耕耘を活用した Chattonella 赤潮制御の試み

    今井, 一郎; 各務, 彰記; 小原, 静夏; 結城, 貴志; 小池, 一彦; 萩原, 悦子; 小川, 憲太; 米山, 弘行
    Diatoms are the most predominant phytoplankton group in the coastal sea and many planktonic diatom species produce resting stage cells in their life cycle to endure unfavorable conditions. These diatom resting stage cells play an important role in initiating the blooms. It is empirically known that diatom cells are sparse in water during the course of red tides of harmful flagellates such as dinoflagellates and raphidophytes. A promising strategy to control the occurrences of red tides by harmful flagellates is to artificially induce diatom blooms just before the development of red tides of harmful flagellates. There usually exist more than...

  6. 日本海風成循環流の季節変化に対する地形性ベータの影響

    朝日, 啓二郎; 磯田, 豊
    A two-layer analytic solution and the two-layer numerical model driven by the wind stress are used to explain the observed seasonal variation of horizontal circulation in the Japan Sea. Special attention is given to the topographic β-effect on the generation of bottom-trapped wave and surface-trapped wave activities on the planetary β plane. The positive curl of wind stress in the northern Japan Sea, where the planetary β in the lower layer is locally canceled by the topographic β, was found to play an important role in the seasonal change of abyssal circulation.

  7. 日本海風成循環流の季節変化に対する地形性ベータの影響

    朝日, 啓二郎; 磯田, 豊
    A two-layer analytic solution and the two-layer numerical model driven by the wind stress are used to explain the observed seasonal variation of horizontal circulation in the Japan Sea. Special attention is given to the topographic β-effect on the generation of bottom-trapped wave and surface-trapped wave activities on the planetary β plane. The positive curl of wind stress in the northern Japan Sea, where the planetary β in the lower layer is locally canceled by the topographic β, was found to play an important role in the seasonal change of abyssal circulation.

  8. 青森県むつ市沖から採集されたカグラザメHexanchus griseus

    河合, 俊郎; 木村, 克也; 川畑, 達; 神, 正人
    A single male specimen of a bluntnose sixgill shark, Hexanchus griseus(Bonnaterre, 1788), was collected from the western North Pacific, off Aomori Prefecture, northern Japan in January 2015. This is the first record of this species from Aomori Prefecture, and the northern-most record of this species around Japanese waters.

  9. 青森県むつ市沖から採集されたカグラザメ Hexanchus griseus

    河合, 俊郎; 木村, 克也; 川畑, 達; 神, 正人
    A single male specimen of a bluntnose sixgill shark, Hexanchus griseus(Bonnaterre, 1788), was collected from the western North Pacific, off Aomori Prefecture, northern Japan in January 2015. This is the first record of this species from Aomori Prefecture, and the northern-most record of this species around Japanese waters.

  10. Inter-oceanic differences in macrozooplankton biomas and community structure in four regions around Hokkaido Island, Japan : consequences for marine ecosystem structure

    Tomiyama, Kosuke; Matsuno, Kohei; Abe, Yoshiyuki; Shimada, Hiroshi; Yamaguchi, Atsushi
    Inter-oceanic differences in macrozooplankton(euphausiids, amphipods, cnidarians and chaetognaths) biomass and community structure were studied in four regions(northern Japan Sea, southern Okhotsk Sea, Donan and Doto areas of North Pacific) around Hokkaido Island. Whole zooplankton biomass ranged between 25 and 315 g WM m-2 and was significantly higher in the southern Okhotsk Sea. Macrozooplankton composed 5-15% of the whole zooplankton biomass. Across all macrozooplankton taxa, the number of species varied with region : the fewest species(2-4 species) were in the southern Okhotsk Sea, followed by the northern Japan Sea(3-5 species), and the most species(4-9 species) were in the Donan and Doto...

  11. Preliminary investigation of the relationships between environmental conditions and landings of North Pacific giant octopus(Enteroctopus dofleini) at Minamikayabe, Hokkaido

    Taguchi, Akira; Sawamura, Masayuki; Bower, John R.
    Relationships between environmental factors and fluctuations in landing of North Pacific giant octopus(Enteroctopus dofleini Wulker, 1910) at Minamikayabe town, Hakodate city, Japan, during 1985-2016 were analyzed using regression analysis. Annual landings ranged between 165 and 403 tons, with an average of 273 tons. The relationship between landings and temperature was significant in 9 of the 24 months examined; 7 of the 9 occurred in catches 3-4 years after the temperature was measured. Rainfall showed no significant relationship with catch amounts. The results of the regression analyses suggest that landings of E. dofleini were related to ocean temperature, especially to temperatures...

  12. Report of a twospot cusk Neobythites bimaculatus from Japan with rare ocellus pattern

    Ohashi, Shinpei; Miyamoto, Kei
    A specimen of twospot cusk Neobythites bimaculatus(237 mm in standard length) was collected in September 2014 from near Okinawa Island, southern Japan. This ophidiid species usually has two distinct ocelli on the dorsal fin and none on the anal fin. In addition, minor ocellus patterns are also known; they include a faint third ocellus rarely on the dorsal fin and two faint ocelli on the anal fin of a smaller specimen (73 mm in standard length). The present specimen possesses both a faint third ocellus on the dorsal fin and a single faint ocellus on the anal fin. This ocellus...

  13. トクビレ科ヤギウオPallasina barbata(Steindachner,1876)の繁殖生態と形態発育

    百田, 和幸; 宗原, 弘幸
    Aspects of the reproductive ecology and early life history of the tubenose poacher Pallasina barbata(Steindachner,1876) were clarified based on observations on the development of eggs without artificial insemination and on morphological changes of larvae and juveniles. The reproductive mode was identified as internal gametic association, which has been reported in several cottoids. The inferred spawning periods and hatching periods were May and March, respectively, suggesting the embryonic period lasted 10 months, which is near the longest known among the Agonids. The eggs were found in the sponge Mycale adhaerens. Newly-hatched larvae were in the flexion stage, and the notochord length(NL)...

  14. イカ内蔵のカドミウム除去に用いるキレート樹脂のカドミウム吸脱着特性

    杉崎, 篤; 喜多, 壮太; 丸山, 英男; 関, 秀司
    Characteristics of the cadmium adsorption and desorption of a chelating resin CR11 was studied. The Langmuir adsorption model modified for the competitive adsorption of cadmium ion and hydrogen ion was applied to describe the effect of pH on the cadmium adsorption of the chelating resin. The adsorption model well described the experimental data and the maximum adsorption capacity and the adsorption constants of cadmium ion and hydrogen ion were determined. The cadmium desorption efficiency form the chelating resin by an eluent(HCI solution) could also be predicted by the adsorption model. The cadmium removal from the eluent by electrolysis was examined...

  15. Iron requirements of Heterosigma akashiwo(Raphidophyceae), Heterocapsa circularisquama(Dinophyceae) and two common centric diatoms

    Fukuzaki, Koji; Yoshioka, Takahito; Sawayama, Shigeki; Imai, Ichiro
    Iron is increasingly recognized to play a key role in the growth of microalgae in various marine systems, but there is a paucity of knowledge about the physiological iron requirements of harmful algal species. This study aimed to elucidate the halfsaturation constant for growth(Ks) and the maximum growth rate(μmax) of four phytoplankton species with regard to iron concentrations. The four species were the fish-killing raphidophyte Heterosigma akashiwo, the bivalve-killing dinoflagellate Heterocapsa circularisquama, and the centric diatoms Ditylum brightwellii(large sized) and Chaetoceros didymus(small sized). We conducted incubation experiments with axenic cultures of the four species using a chemically defined synthetic medium....

  16. Trailing the Effectiveness of a Modified Trawl Net in the Northern Java Sea, Indonesia

    Pramitasari, Sulistyani Dyah; Okamoto, Junichiro; Yoshimura, Mika; Kimura, Nobuo
    Overfishing has occurred in several regions around Indonesia, including the Northern Java Sea, primarily due to the large number of artisanal fishers and fishing boats, and the use of "un-environmentally friendly fishing gear", such as trawl nets. Consequently, Presidential Decree No.39 was enacted on July 1, 1980, which prohibited trawl operations in Indonesia to reduce fishing and social conflicts, and to protect resources. Fishers have responded to this government regulation by modifying their gear to elude its enforcement. However, these modifications are oriented more economic than conservation benefits. To rectify this issue, an environmentally-frendly trawl net that enables resource conservation...

  17. 宗谷暖流域における反時計回り非線形渦流列の励起機構

    伊田, 智喜; 有田, 駿; 磯田, 豊
    The generation mechanism of anti-clockwise nonlinear eddy street along the Soya Warm Current is examined using the inflow-forced numerical model incorporating the simple shelf-slope topography. According to the conservation of potential vorticity, a strong positive vorticity is produced off the inflow entrance by vortex stretching as the water column is pushed out to deeper offshore. It rapidly grows up an isolated anti-clockwise circular eddy, i.e., a nonlinear eddy, during advection time traveling round the eddy. Therefore, this advection time controls the oscillated period, and each isolated eddy is periodically generated and stably advected downstream by the mean shear-flow. Such flow...

  18. 北太平洋風成循環流の季節変化に関する数値モデル実験

    舘野, 愛実; 藤原, 将平; 磯田, 豊; 朝日, 啓二郎
    A two-layer model ocean with Izu-Ogasawara Ridge(IOR) and the Emperor Seamounts(ESs), driven by seasonally varying wind stress, is used to explain the observed seasonal variations of barotropic and baroclinic response in the North Pacific. Since isostasy is achieved for annual mean state, the annually averaged subarctic and subtropical surface gyres are separated without any bathymetric influence. For a short time scale such as seasonal variation, the barotropic flow is inhibited from ascending the bottom slope because of the restriction of the potential vorticity conservation, and generates the baroclinic Annual Rossby Waves(ARW) through the impinging process on the shelf slope. The...

  19. Seasonal changes in mesozooplankton swimmer community and fecal pellets collected by sediment trap moored at the Northwind Abyssal Plain in the western Arctic Ocean

    Matsuno, Kohei; Yamaguchi, Atsushi; Fujiwara, Amane; Onodera, Jonaotaro; Watanabe, Eiji; Harada, Naomi; Kikuchi, Takashi
    In the western Arctic Ocean, the long sea ice coverage period prevents year-round seasonal zooplankton sampling by ordinary ship-board observation. To overcome these problems, the analysis of zooplankton swimmers in samples collected by a year-round moored sediment trap may be a powerful tool. In this study, we studied seasonal changes in zooplankton swimmer community and fecal pellets collected by a sediment trap moored at fixed depths(180-260m) of the Northwind Abyssal Plain in the western Arctic Ocean from October 2010 to September 2012. The fecal pellets were separated into four types : oval, cylinder, spherical and brown-colored pellets. The occurrence of...

  20. 北海道近海産マイナー魚28種の脂質特性

    中塚, 美紀子; 安藤, 靖浩
    Lipid content, lipid class composition, and fatty acid composition were determined for 28 minor marine fish species caught from the waters around Hokkaido, Japan. The samples include some rare fish such as dusky rockfish Sebastes variabilis "nagamenuke" and prowfish Zaprora silenus "bouzuginpo." Most samples had low lipid contents, and therefore, can be used in low-fat fish foods. In contrast, the fish of four species and the liver of eight species were rich in lipid as they contained triacylgycerols or diacylglycerylethers as major lipid classes. Such fatty fish can be used as a source of marine lipids. The liver of brown...

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