Research activity information

• Application of satellite remote sensing data for predicting the occurrence of hypoxia at the seabed: a case study in Funka Bay, Japan
  Hiroto Abe; Akihiro Sasaki; Hiroji Onishi; Atsushi Ooki; Tetsuya Takatsu; Takahiro Iida; Naoto Kobayashi; Keiichiro Sakaoka; Tsubasa Chujo; Soya Sakuma; Shintaro Ohno
  International Journal of Remote Sensing, 1, 22, Informa UK Limited, 09 Jan. 2026
  Scientific journal
• Transport and modification processes of dense Soya Current Water in the boundary region between shelf and basin areas off Abashiri
  千葉 彩; 堀尾 一樹; 磯田 豊; 小林 直人
  海の研究, 30, 2, 15, 46, 日本海洋学会, Mar. 2021, [Peer-reviewed]
  Japanese
• Observation and model experiments on an internal-wave packet accompanied by streak bands over the sill topography of Tsugaru Strait
  Yamaguchi Takuya; Isoda Yutaka; Itoh Umihiko; Mukai Touru; Kobayashi Naoto
  Oceanography in Japan, 29, 3, 71, 90, The Oceanographic Society of Japan, 2020, [Peer-reviewed]
  Japanese,

  The Synthetic Aperture Radar (SAR) around the western entrance of the Tsugaru Strait has yielded well-defined images of an internal-wave packet accompanied by two or three surface-streaks (surface convergence within the same water mass), which is active during the stratified season, and whose wavelength is in the order of several hundred meters. Most of the waves in the packet were observed near the topographically shallow parts of the sill. Temporal changes were repeatedly observed in the internal waves confined to the sill using a high-frequency echosounder profiler within one-day in the summer 2017. The acoustic images suggest that a wave packet of extraordinary amplitude (> 150 m) has developed transiently around the downstream side of the sill at the ascending passage flow. This wave packet consists of two or three successive streak bands, with very disturbed sea surface conditions overlying wave troughs, i.e., strong downwelling areas. The dynamics of such waves developing over the sill is studied through a fully nonlinear nonhydrostatic numerical model. The vertical fluid stratification and temporal change of the barotropic passage flow were adjusted to approximate our observation conditions. The results suggest that the wave packet is effectively amplified near the downstream side of the sill, where the Froude number becomes a critical point, because upstream propagating waves on the sill slope stagnate and overlap efficiently. In this dynamical process, however, even if the wave grows to large amplitude, it does not form a well-organized solitary wave, but is rather scattered due to the strong dispersion of waves.

• Isoprene production in seawater of Funka Bay, Hokkaido, Japan
  Atsushi Ooki; Ryuta Shida; Masashi Otsu; Hiroji Onishi; Naoto Kobayashi; Takahiro Iida; Daiki Nomura; Kota Suzuki; Hideyoshi Yamaoka; Tetsuya Takatsu
  Journal of Oceanography, 75, 6, 485, 501, Springer Science and Business Media LLC, Dec. 2019, [Peer-reviewed]
  Scientific journal
• Annual and seasonal changes in the assemblage of planktonic copepods and appendicularians in Funka Bay before and after intrusion of Coastal Oyashio Water
  Hideyoshi Yamaoka; Tetsuya Takatsu; Kota Suzuki; Naoto Kobayashi; Atsushi Ooki; Mitsuhiro Nakaya
  Fisheries Science, Sep. 2019, [Peer-reviewed]
  English, Scientific journal
• Numerical experiments of surface clockwise circulation in Funka Bay during early summer
  Kobayashi Naoto; Isoda Yutaka; Horio Kazuki
  Oceanography in Japan, 28, 4, 51, 74, The Oceanographic Society of Japan, 2019, [Peer-reviewed], [Lead author]
  Japanese,

  A current system consisting of surface clockwise circulation is the most remarkable feature observed in Funka Bay during early summer. The present study investigates its formation process using a numerical model driven by the following three factors during the typically strati fied season, i.e., (1) freshening of coastal water because of river discharge, (2) density inflow of Tsugaru Gyre water, and (3) surface heat flux. It was found that the "topographic heat accu mulation effect" resulting from surface heating is essential for the genesis of the surface clock wise circulation. Because of the surface offshore flow generated by the thermal contrast be tween the shallow coastal and deep central regions, a weak anti-clockwise geostrophic flow is initially formed. Nevertheless, with continuous thermal forcing, after a few months, this offshore flow gradually reinforces the upslope transport of cold dense water. When the cooling resulting from the dense water upslope dominates in comparison to the downward heating resulting from vertical diffusivity around the coastal sea bottom, the coastal water is relatively colder than the offshore surface water. Therefore, shallowing of the interface toward the coast drives the geos trophic flow proceeding along the coast to the left-handed side. In response to this change, an isolated clockwise circulation begins to establish from the surface layer of the northern bay head, while an initially formed anti-clockwise flow migrates to the deeper region.

• Observations and model experiments of the diurnal eddy of the Cold Water Belt along the offshore side of the Soya Warm Current
  Iida Hiroyuki; Isoda Yutaka; Kobayashi Naoto; Horio Kazuki
  Oceanography in Japan, 27, 4, 155, 174, The Oceanographic Society of Japan, 2018, [Peer-reviewed]
  Japanese,

  The detailed distributions of flow, temperature fields, and the temporal change of diurnal eddies accompanied with the Cold Water Belt (CWB) are observed by CTD and one-day repeated XBT/ADCP measurements across the Soya Warm Current (SWC) in the summer of 2016. Saline water originating from the Japan Sea Intermediate Water (JSIW) was found below the CWB. Tracer experiments using numerical models predict the offshore-side water of the SWC is supplied by onshore advection and upwelling of the deeper JSIW. The nearly homogeneous JSIW is taken into a counter-clockwise isolated eddy, which is periodically generated by the diurnal tidal current around the Soya Strait and is advected downstream along the offshore side of the SWC. Therefore, the majority of the water below the CWB, which is weakly stratified, is composed of this eddy street.

• Seasonal variation of volatile organic iodine compounds in the water column of Funka Bay, Hokkaido, Japan
  Yusaku Shimizu; Atsushi Ooki; Hiroji Onishi; Tetsuya Takatsu; Seiji Tanaka; Yuta Inagaki; Kota Suzuki; Naoto Kobayashi; Yoshihiko Kamei; Kenshi Kuma
  JOURNAL OF ATMOSPHERIC CHEMISTRY, 74, 2, 205, 225, Jun. 2017, [Peer-reviewed]
  English, Scientific journal
• Inflow process of low potential vorticity water originating from the intermediate waters of the Japan Sea into the Tsugaru Strait
  Ida Satoki; Yamashita Shinji; Isoda Yutaka; Kobayashi Naoto
  Oceanography in Japan, 25, 4, 101, 122, The Oceanographic Society of Japan, Jul. 2016, [Peer-reviewed]
  Japanese, Based on hydrographic observations of the inflow pathway from the Japan Sea into the Tsugaru Strait, we find that upwelled cold water originating from the intermediate waters of the Japan Sea is concentrated along the narrow shelf to the west of Hokkaido; its modified water is transported into the strait via horizontal advection through a counterclockwise circulation. The dynamics of this inflow process are investigated using barotropic numerical models that incorporate realistic bathymetry. The primary driving force of the current system is the sea level difference across the strait. The numerical modeling experiments simulate the observed pathway, which is nearly conservative following low potential vorticity and originates from a thick water column in the offshore deep area. This pathway is highly sensitive to local bottom topography such that the Mastumae Caldron has a major impact on the formation of the counterclockwise circulation. If the shelf topography along the west coast of Hokkaido had a gentler slope, a southward coastal current with high potential vorticity along the shelf could be established after the northward passage of shelf wave disturbances generated at the strait. However, the actual topographic condition, i.e., a steep slope, drastically slows the propagation speed of shelf waves and strongly suppresses the genesis of a southward coastal current. Therefore, the inflow water into the strait must be supplied by onshore advection of deeperwaters, which results in the inflow pathway being characterized by low potential vorticity.
• Regeneration dynamics of iron and nutrients from bay sediment into bottom water of Funka Bay, Japan
  Nanako Hioki; Kenshi Kuma; Yuichiroh Morita; Daichi Miura; Atsushi Ooki; Seiji Tanaka; Hiroji Onishi; Tetsuya Takatsu; Naoto Kobayashi; Yoshihiko Kamei
  JOURNAL OF OCEANOGRAPHY, 71, 6, 703, 714, Dec. 2015, [Peer-reviewed]
  English, Scientific journal
• Effects of hypoxia on the feeding intensity and somatic condition of the blackfin flounder Glyptocephalus stelleri in Funka Bay, Japan
  Yuta Inagaki; Tetsuya Takatsu; Takao Uenoyama; Noriko Yoneda; Shinichi Yokoyama; Yoshihiko Kamei; Naoto Kobayashi; Toyomi Takahashi
  FISHERIES SCIENCE, 81, 4, 687, 698, Jul. 2015, [Peer-reviewed]
  English, Scientific journal
• Production and sea-to-air flux of organic iodine gases associated with degradation of organic matter after diatom bloom in coastal sea area
  Shimizu Yusaku; Ooki Atsushi; Kuma Kenshi; Onishi Hiroji; Kamei Yoshihiko; Kobayashi Naoto
  Abstracts of Annual Meeting of the Geochemical Society of Japan, 62, 89, 89, GEOCHEMICAL SOCIETY OF JAPAN, 2015
  Japanese, CH₂I₂、C₂H₅Iなど揮発性有機ヨウ素化合物（volatile organoiodine compound:VOI）は、海から大気へヨウ素を供給するキャリアーとして機能する。本研究では、VOIと生物生産性や有機物分解との関係を調べるために、北海道噴火湾で2012年3月から2014年12月の隔月に海水を採取し、海水中VOI濃度をパージ＆トラップ-ガスクロマトグラフ-質量分析法で測定した。
  春季植物プランクトンブルーム終了後の5月以降にVOI濃度は急激に増加し始め、6月から7月に年間ピークに達した。ピーク深度はVOI成分により異なった。このようなピーク深度の違いは、生成メカニズムの違いを示しており、こうした海水中VOIの生成メカニズムの違いは、大気への放出特性にも反映されると考えられる。
• Inverse Estuary Circulation in Mutsu Bay-(1) Hydrographic Observations during the Summer-time-
  河野航平; 磯田豊; 工藤勲; 藤原将平; 有田駿; 小林直人; 吉田達; 扇田いずみ; 高津哲也
  海と空, 90, 1, 11, 16, 海洋気象学会, 31 Aug. 2014, [Peer-reviewed]
  Japanese, Scientific journal
• Improved growth of flathead flounder Hippoglossoides dubius in hypoxic waters in Funka Bay, Japan
  Yuta Inagaki; Tetsuya Takatsu; Masafumi Kimura; Yota Kano; Toyomi Takahashi; Yoshihiko Kamei; Naoto Kobayashi; Tatsuaki Maeda
  FISHERIES SCIENCE, 80, 4, 725, 734, Jul. 2014, [Peer-reviewed]
  English, Scientific journal
• Time series observation of volatile organoiodide compounds in Funka Bay, Hokkaido
  Shimizu Yusaku; Ooki Atsuhi; Kuma Kenshi; Oonishi Hiroji; Kamei Yoshihiko; Kobayashi Naoto
  Abstracts of Annual Meeting of the Geochemical Society of Japan, 61, 202, 202, GEOCHEMICAL SOCIETY OF JAPAN, 2014
  Japanese, CH₂I₂などの海水中の揮発性有機ヨウ素化合物(Volatile organoiodine compound；VOI)は、海洋から大気へのヨウ素の主なキャリアーとして知られるが、生成過程などは明らかになっていない。本研究では、VOIと生物生産性や有機物分解との関係を明らかにするため、VOIと生物化学パラメータのモニタリングを行った。北海道噴火湾にて、VOI（CH₂I₂、CH₃I、CH₂ClI）濃度や、生物科学パラメータの定点測定を、2012年3月から2014年6月まで行った。春季の植物プランクトンブルームが終焉し、植物プランクトンが老化、死滅する時期に、VOIが多量に生成されることがわかった。CH2I2増分が2013年は2012年の半分であったことより、VOI生成量には経年差がみられた。
• Seasonal variations of bromoform distribution in the Funka Bay
  OOKI Atsushi; MIWA Kazuji; ONISHI Hiroji; KAMEI Yoshihiko; KOBAYASHI Naoto; KUMA Kenshi
  Bunseki Kagaku, 62, 12, 1071, 1078, Dec. 2013, [Peer-reviewed]
  Japanese, Scientific journal
• The Kyucho passing through the bay mouth of Funka Bay-(3) Numerical model experiment II-
  小林直人; 磯田豊; 高津哲也; 木村修; 亀井佳彦
  海と空, 88, 3, 57, 63, 海洋気象学会, 22 Mar. 2013, [Peer-reviewed], [Lead author]
  Japanese, Scientific journal
• The Kyucho passing through the bay mouth of Funka Bay-(2) Numerical model experiment I-
  小林直人; 磯田豊; 高津哲也; 木村修; 亀井佳彦
  海と空, 88, 2, 43, 48, 海洋気象学会, 30 Nov. 2012, [Peer-reviewed], [Lead author]
  Japanese, Scientific journal
• The Kyucho passing through the bay mouth of Funka Bay-(1) Data analysis-
  小林直人; 磯田豊; 小林雅行; 佐藤千鶴; 木村修; 山口秀一; 高津哲也; ROSA Ana Luisa
  海と空, 88, 1, 9, 20, 海洋気象学会, Jul. 2012, [Peer-reviewed], [Lead author]
  Japanese, Scientific journal
• Intrusion of the Oyashio water into the eastern mouth of Tsugaru Strait in early summer, 2003
  Hiroshi Kuroda; Yutaka Isoda; Hidetaka Takeoka; Kenshi Kuma; Satoshi Honda; Hiromi Matsuura; Yukiyo Saitoh; Hyoe Takata; Shoei Iwade; Taku Wagawa; Naoto Kobayashi
  CONTINENTAL SHELF RESEARCH, 32, 36, 46, Jan. 2012, [Peer-reviewed]
  English, Scientific journal
• The Kyucho occurred off Kameda Peninsula, Hokkaido, at the end of May, 2006
  小林直人; 磯田豊; 小林雅行; 佐藤千鶴; 木村修; 山口秀一; 高津哲也; ROSA Ana Luisa
  北海道大学水産科学研究彙報, 58, 3, 29, 41, 北海道大学大学院水産科学研究院 = Research Faculty of Fisheries Sciences, Hokkaido University, Feb. 2009
  Japanese, A large damage to fishing set-nets caused by the Kyucho occurred off Kameda peninsula on 30 May, 2006. Such Kyucho seldom occurs in this area and hence it is unusual phenomenon. Two current-meters setting off Usujiri located at Kameda peninsula and off Shiraoi faced the Hidaka Bay captured this sudden and swift current. The meteorological and oceanographical conditions in 2005 without the Kyucho and those in 2006 with the Kyucho were compared. The difference in both years was the oceanic stratification. That is, the surface halocline was thinly formed by a large quantity of rainfall water accompanied by the atmospheric disturbance on 28 May in 2006, before the Kyucho occurrence. In the case of such discontinuity subsurface thinner layer than usual, we will expect that the particle velocity of wind-induced internal Kelvin wave increases, but its phase propagation speed rather decreases. In fact, the observed surface current velocity (0.3-1.2 m/s) is almost as same as the estimated propagation speed (0.3-0.8 m/s).
• Processes Influencing Iron Distribution in the Coastal Waters of the Tsugaru Strait, Japan
  Yukiyo Saitoh; Kenshi Kuma; Yutaka Isoda; Hiroshi Kuroda; Hiromi Matsuura; Taku Wagawa; Hyoe Takata; Naoto Kobayashi; Seiya Nagao; Takeshi Nakatsuka
  JOURNAL OF OCEANOGRAPHY, 64, 6, 815, 830, Dec. 2008, [Peer-reviewed]
  English, Scientific journal
• Tsushima Warm Current Water inflow to Tsugaru Strait
  中嶋與文; 磯田豊; 松浦宏美; 和川拓; 相木智一; 矢部いつか; 高田兵衛; 久万健志; 小林直人; 矢幅寛
  海と空, 84, 1, 1, 16, 海洋気象学会, 30 Jun. 2008, [Peer-reviewed]
  Japanese
• Transportation of pointhead flounder Cleisthenes pinetorum larvae in Funka Bay and its vicinity
  栗藤亜希子; 平岡優子; 高津哲也; 伊村一雄; 小林直人; 亀井佳彦
  水産海洋研究, 69, 3, 145, 155, 水産海洋学会, Aug. 2005, [Peer-reviewed]
  Japanese

• Water mass redistribution and consequent vertical mixing due to passage-flow over the sill-topography at the western entrance of the Tsugaru Strait
  Yamane Towa; Isoda Yutaka; Nishioka Yu; Echigo Yurika; Fujii Yu; Wakita Masahide; Yamazaki Tomoyasu; Kobayashi Naoto; Iida Takahiro; Kaneko Hitoshi, 北海道大学水産科学研究彙報, 74, 1, 35, 58, 04 Aug. 2024
  Extensive hydrographic observations traversing the Tsugaru Strait using a research vessel were carried out in spring 2021 and summer 2022. In both seasons, in addition to the inflow of Tsushima Warm Current Water from the western entrance of the strait, water mass originating in the middle layer of the Japan Sea, i.e., Japan Sea Intermediate Water (JSIW), intruded into the strait from the bottom layer on the Hokkaido (northern) side. In the downstream of the sill-topography located at the western entrance, density stratification rapidly weakened, concurrently with disappearance of JSIW properties. In order to investigate key physical drivers of the observed water mass distribution and its modification, the numerical experiments were conducted on stratified fluid passing over a trapezoidal-shaped sill feature in the channel model with a simple rectangular cross section. Even without the sill, vertical circulation, which is accompanied by upwelling along Hokkaido (northern) coast and density inversion near the sea bottom, is formed by the northward bottom Ekman flow caused by the eastward passage-flow. When the silltopography is added to this, vertical circulation is further enhanced by driving of“ pseudo-bottom Ekman flow” on both its upstream and downstream slopes. Near the Hokkaido (northern) coast in the downstream of the sill, offshore (southward) surface flow connected to coastal upwelling moves the velocity maximum of the passage-flow to the Aomori (southern) side. Density inversion reaching the sea surface from the sea bottom expanded off Hokkaido (northern) coast locally, and the gravitationally unstable vertical mixing occurred there. These results suggest that sill-topography promotes water mass redistribution and local vertical mixing associated with vertical circulation on the transverse section, resulting in active water mass modification even in short channels such as the Tsugaru Strait., Faculty of Fisheries Sciences, Hokkaido University, Japanese
• Spawning ground selection and larval feeding habits of Arabesque greenling Pleurogrammus azonus around the Matsumae Peninsula, Japan
  Tetsuya Takatsu; Tomoaki Toyonaga; Shin’ya Hirao; Eri Ooka; Naoto Kobayashi; Mitsuhiro Nakaya, Fisheries Science, 90, 3, 435, 452, 03 Apr. 2024, [Peer-reviewed]
  Springer Science and Business Media LLC
• Long-lived Clockwise Topographic Separation Vortices with Strong Vertical Circulation at the Eastern Outlet of the Tsugaru Strait
  ISHIZAKI Yuuya; ISODA Yutaka; TAYA Koushiro; KOBAYASHI Naoto, Bulletin on Coastal Oceanography, 61, 1, 1, 19, Aug. 2023, [Peer-reviewed]
  Coastal Oceanography Research Committee, the Oceanographic Society of Japan, Japanese
• Vertical circulation induced by negative shear flow at the downside of Ooma-zaki in the Tsugaru Strait
  Asano Ryuta; Isoda Yutaka; Kobayashi Naoto; Nakamura Tomohiro; Itoh Kaoru, Bulletin of Fisheries Sciences, Hokkaido University, 70, 1, 63, 76, 24 Aug. 2020
  北海道大学大学院水産科学研究院, Japanese
• 陸奥湾における1989-2019年マダラ着底稚魚分布密度調査による加入量予測
  高津哲也; 中屋光裕; 神山晃汰; 亀井佳彦; 小林直人; 飯田高大; 野呂恭成, 水産海洋研究, 84, 3, 2020, [Peer-reviewed]
• Numerical experiment for a westward tail of the Tsugaru Gyre along the Hidaka shelf slope
  Naoto Kobayashi; Yutaka Isoda; Keijiro Asahi; Faculty of Fisheries Hokkaido University; Graduate School of Fisheries Science Hokkaido University; Graduate School of Fisheries Science Hokkaido University, 海の研究 = Umi no Kenkyu (Oceanography in Japan), 24, 5, 171, 187, 15 Sep. 2015, [Peer-reviewed]
  単純化した陸棚地形上への流入水の挙動に関わるf平面σ座標系数値モデル実験によって,初夏に津軽Gyreが日高湾陸棚斜面上に侵入したときに生じることが最近の海洋観測で確認された分岐流の形成・発達過程を調べた。成長を続ける津軽Gyreが侵入する北部陸棚斜面域には海底捕捉モードと表層捕捉モードの2種類の低周波擾乱が同時に存在し,斜面上の下層水柱は連続的に押し縮められ,負の相対渦度を生成する。その結果として,侵入域の西側ではほぼ順圧もしくは海底捕捉の時計回り渦流擾乱が形成され,分岐域から陸棚斜面に沿って西方へ伝播する。侵入域の東側では反時計回りの渦流擾乱が形成され,沖合の底層低温水を沿岸域へ定常的に供給する。この現象は津軽Gyreが北岸境界に沿った鏡像効果によって東方移動することを抑える働きをする。このようにして,分岐直後の渦流は日高湾陸棚斜面に沿って西方へ引き延ばされる津軽Gyreにまで発達することがわかった。A recent hydrographic survey indicated that a local bifurcation of the Tsugaru Gyre, which appeared over the Hidaka shelf slope in early summer, accompanied a clockwise, small eddy. To examine the bifurcation's formation and development processes, we performed a numerical experiment using an f-plane σ-coordinate model with idealized shelf topography. During the stage at which the Tsugaru Gyre grew and intruded into the northern shelf slope area, the lower-layer water column on the slope was continuously contracted to induce a negative relative vorticity. As a consequence, the nearly barotropic or bottom-trapped motion with clockwise rotation emanated west of the intrusion area and then propagated westward along the slope. This motion was associated with two types of low-frequency waves characterized by surface and bottom intensifications. On the contrary, an anti-clockwise eddy formed east of the intrusion area and stably fed on the offshore bottom cold water into the coastal area. These processes suppressed the eastward shift of the Tsugaru Gyre by the mirror effect of the lateral boundary. Thus, the above-mentioned small eddies were found to dominate the Tsugaru Gyre, shifting westward along the Hidaka shelf slope., 日本海洋学会, Japanese
• The bifurcation of the Tsugaru Gyre over the Hidaka shelf slope
  小林 直人; 太田 紗生; 磯田 豊, 海と空 = Sea and sky, 90, 1, 1, 10, Aug. 2014, [Peer-reviewed]
  海洋気象学会, Japanese
• 北海道西岸沖のホタテ貝種苗生産を支える産卵及び浮遊幼生の輸送過程
  磯貝 安洋; 磯田 豊; 下野 学; 小林 直人; 工藤 勲; 干場 康博, 北海道大学水産科学研究彙報 = Bulletin of Fisheries Sciences, Hokkaido University, 60, 2, 23, 37, Dec. 2010
  北海道大学大学院水産科学研究科, Japanese
• Seasonal Variations of Surface Flow Patterns in the Nemuro Strait
  MORI Fumihiro; ISODA Yutaka; ABE Syoko; KOBAYASHI Naoto; YAHABA Hiroshi; ISOGAI Yasuhiro; Fumihiro Mori; Yutaka Isoda; Syoko Abe; Naoto Kobayashi; Hiroshi Yahaba; Yasuhiro Isogai; Graduate School of Environmental Science Hokkaido University; Graduate School of Fisheries Sciences Hokkaido University; Graduate School of Environmental Science Hokkaido University; Faculty of Fisheries Sciences Hokkaido University; Graduate School of Fisheries Sciences Hokkaido University; Graduate School of Fisheries Sciences Hokkaido University, Oceanography in Japan, 19, 2, 89, 110, 15 Mar. 2010, [Peer-reviewed]
  根室海峡における表層流の季節変化を記述するために,長期の実測表層流(ADCPとGEK),風向風速,沿岸水位,沿岸水温,スナップショットの海洋観測データの解析を行なった。表層流が一年周期の正弦曲線で表現できるような季節変化は海峡南端付近にみられ,5-8月は北太平洋側から海峡内方向への流入,他の月は海峡側から北太平洋への流出を示した。しかしながら,この流入流出は海峡内における流れパターンの季節変化とは必ずしも連動していないようである。北西風が卓越する冬季の海峡内では南下する海峡通過流が示されたが,この南下流は風駆動による吹送流が海峡南端の流出流と一時的に繋がった流れと推測される。他の季節は春と秋に極大をもつ南西風が卓越する時期である。春季の海峡北部にある深い水深の海域(知床半島の南側)では,北側で北上流,南側で南下流となる二分岐流が形成され,この流れパターンは安定して秋季まで継続する。二分岐後の北上流は春と秋に南西風が強まる時期に同期して強まる傾向を示すことから,この二分岐流は吹送流として説明できる可能性が示唆される。一方,二分岐後の南下流は,夏季の海峡中間部の浅瀬付近から現れ,秋季には海峡南部で支配的となる西流によって次第に分断されていくようにみえる。Long-term direct current velocity (GEK and ADCP), wind, coastal sea level, coastal water temperature and snapshot hydrographic data were used to describe the typical seasonal variations of surface flow patterns in the Nemuro Strait. At the southern end of the Strait, we find a remarkable seasonal change with a clear one-year cycle in the inflow into the Strait (May to August) and the outflow to the North Pacific (other months). However, it seems that such in/outflow variation never synchronize with the seasonal flow patterns in the Strait. During the winter season when the northwesterly wind brows, we infer that the southward wind-induced passage-flow through the Strait may transiently connect to the outflow at the southern end of the Strait. During the other seasons when the southwesterly wind is intensified at two times in spring and autumn, stable bifurcation flow (i.e., the northern northward and southern southward branch flows) forms around the deeper area at the northern part of the Strait (i.e., south of the Shiretoko peninsula). Since the northward branch flow strengthens at the corresponding season of intensified southwesterly wind, one possible mechanism of bifurcation flow is the wind-driven current. On the other hand, the southward branch flow is gradually interrupted by the westward flow, which begins to appear around the shallower area at the central part of the Strait in summer and dominates at the southern Strait in autumn., 日本海洋学会, Japanese
• Seasonal Variations of Shelf Circulation in Hidaka Bay, Hokkaido, Japan, with an Interpretation of the Migration Route of Juvenile Walleye Pollock
  ROSA ANA LUISA; ISODA YUTAKA; KOBAYASHI NAOTO, Journal of oceanography, 65, 5, 615, 626, 01 Oct. 2009, [Peer-reviewed]
  Oceanographic Society of Japan, English
• Tsushima Warm Current Water inflow to Tsugaru Strait
  NAKAJIMA Yobun; ISODA Yutaka; MATSUURA Hiromi; WAGAWA Taku; AIKI Tomokazu; YABE Itsuka; TAKATA Hyoue; KUMA Kenshi; KOBAYASHI Naoto; YAHABA Hiroshi, 海と空, 84, 1, 1, 16, 30 Jun. 2008, [Peer-reviewed]
  海洋気象学会, Japanese
• Water mass modification process of the passage-flow waters through the Tsugaru Strait
  松浦宏美; 磯田豊; 黒田寛; 久万健志; 斉藤雪美; 小林直人; 相木智一; 和川拓; 矢部いつか; 干場康博, 海と空, 83, 1, 21, 35, 2007, [Peer-reviewed]
• Seasonal Variations of the Flow Pattern and Water Masses off Kameda Peninsula, Hokkaido
  Kobayashi Naoto; Isoda Yutaka; Kuroda Hiroshi; Kimura Osamu; Yamaguchi Hidekazu; Onishi Mitsuyo; Rosa Ana Luisa, Bulletin on coastal oceanography, 44, 1, 59, 67, 2006, [Peer-reviewed], [Lead author]
  Seasonally varying nearshore currents, which have not been described in the oceanographic literature, are believed to exist off Kameda Peninsula, Hokkaido; a northwestward current called the "Shikabe-jio", and a southeastward current called the "Esan-jio". The purpose of this study is to describe these currents quantitatively and to examine the relationship between seasonal variations in currents and water mass distribution by analyzing CTD and ADCP data. We have confirmed the seasonal variation of flow patterns with opposite current direction, i.e., the baroclinic southwestward flow (Esan-jio) from spring to summer and the barotropic weak northwestward flow (Shikabe-jio) in winter. Tsugaru Warm Current Water appears off the Peninsula with transitional changes of current in autumn, but rapidly replaces Oyashio Water in winter., 日本海洋学会沿岸海洋研究部会, Japanese
• Development of a Simultaneous Chemiluminescent Immunoassay for Bigeye Tuna, Thunnus obesus, Vitellogenin
  AMANO Haruna; FUKADA Haruhisa; FUJITA Toshiaki; KOBAYASHI Naoto; SAKAOKA Keiichirou; HARA Akihiko, 水産増殖, 52, 3, 293, 300, 2004, [Peer-reviewed]
  ハイドロキシルアパタイトおよびゲル濾過カラムを用いて、Vgの構成成分である卵黄蛋白Lvをメバチマグロ卵巣から精製した。精製Lvはゲル濾過において300kDa、SDS-PAGEでは105kDaであった。Lvを抗原とした特異抗体は、Western blottingでは雄血清とは反応せず、雌血清とのみ特異的に反応した。雌血清で観察されたバンドは210kDaであり、Vgであると考えられた。精製Lvをスタンダードとしアクリジニウム標識抗体を用いて、simultaneous CLIAによるメバチマグロVg測定系を確立した。測定範囲は0.97－1000 ng／mlであり、卵抽出液と雌血清の希釈系列は精製Lvスタンダードカーブと平行性を示した。アッセイ内およびアッセイ間変動係数は10％未満であった。さらに、本測定系はクロマグロ、キハダマグロおよびブリと免疫交叉性を示した。ハワイ沖で捕獲したメバチマグロ雌魚では7個体中3個体からVgが検出され、雄個体からVgは検出されなかった。, 水産増殖談話会, Japanese
• Quick-Offer of Current Information using T/V ADCP -Program for Quality Contral of ADCP Data-
  Kobayashi Naoto; Isoda Yutaka; Takatsu Tetsuya; Yamaguchi Shuichi; Kimura Osamu, Bulletin of Fisheries Sciences, Hokkaido University, 55, 2, 97, 103, 2004, [Lead author]
  Hokkaido University, Japanese
• Wave Fluctuation with the Passage of a Depression
  YONETA Kunisaburo; MEGURO Toshimi; KAJIWARA Yoshiyuki; SAKAOKA Keiiciro, Bulletin of Fisheries Sciences, Hokkaido University, 53, 1, 51, 55, 2002
  Hokkaido University, English
• Wave Fluctuation with the Passage of a Depression
  Bulletin of Fisheries ･ Sciences, Hokkaido University, 53, 1, 51, 55, 2002
• Results of the 2001 Salmon Research Cruise of the Hokusei Maru
  NPAFC Doc., 548, 2001
• Results of 2000 Salmon Research Cruise of the Hokusei Maru
  NPAFC Doc., 486, 2000
• Characteristics of standard methods of Norpac net towing in the high latitude sea area II. Overtowing under rough sea conditions and estimation of zooplankton abundance
  ODATE Tsuneo; SAKAOKA Keiitiro; KAJIWARA Yoshiyuki; IMAI Keiri; KOBAYASHI Naoto; MEGURO Toshimi; FUKUTI Mitsuo, Bulletin of the Plankton Society of Japan, 46, 2, 134, 142, 1999
  日本プランクトン学会, Japanese
• Baroclinic Flow Referred to the 3000 m Reference Level across the 180゜ Transect in the Sabarctic North Pacific
  Ohtani Kiyotaka; Onishi Hiroji; Kobayashi Naoto; Anma Gen, Reprinted from Bulletin of the Faculty of Fishries Hokkaido University, 48, 3, 53, 64, 1997
  Hokkaido University, English

• THE OCEANOGRAPHIC SOCIETY OF JAPAN

• 北海道大学水産学部附属練習船による海洋漁業調査
  2001
• 北海道大学水産学部附属練習船による海洋漁業調査
  2000

• Verification of the turbulence and light-intensity hypotheses on larval survival of flathead flounder
  Grants-in-Aid for Scientific Research
  2008 - 2011
  TAKATSU Tetsuya; ISODA Yutaka; KOBAYASHI Naoto
  Faster-growing larvae of flathead founder Hippoglossoides dubius in the initial feeding stage showed higher survival rate than slower-growing ones within cohort in Funka Bay, Hokkaido. The larvae of 2007 year-class that experienced warm-water-temperature condition showed the fastest growth in 2007-2011 year-classes. Contrary to expectations, the 2008 year-class that showed slowest-growing in larval stage became a strong year class in mature stage. Growth rate in the initial feeding stage was weakly correlated with wind speed as a turbulence indicator however did not with water temperature, global solar radiation, or density of copepod nauplii as principal prey for flathead founder larvae. Match-mismatch and growth-mortality hypotheses in initial feeding stage have some degree of validity but are insufficient to explain the variability seen in recruitment. The survival in later stage may determine the recruitment success.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, 20580189
• 北海道亀田半島東岸沖で発生した急潮現象
  2006
  2006年5月29日から30日にかけて、北海道南西部に位置する亀田半島の鹿部から川汲に至る沿岸海域で、北側から順に漁業施設が破損する被害が発生した。このとき、亀田半島東岸沖では鹿部から恵山方向へ向かう非常に強い南東流であったことが漁業者から報告されている。しかし、このような急潮の発生報告は過去にはほとんどなく、この海域で急潮が発生することは非常に珍しい。この急潮が発生した初夏の平均的な海況は、主に雪解け水による表層付近の塩分躍層の発達が特徴であり、その表層の平均流は弱い南東流(0.2～0.5kt)である(小林ほか、2006)。本研究の目的は、2005年に限って、なぜ急潮が発生したのか、その原因および発生メカニズムを調べることにある。
  Competitive research funding
• 北海道亀田半島沖の恵山潮と鹿部潮
  2005
  Competitive research funding
• Study on the sampling properties of the plankton nets.
  Grants-in-Aid for Scientific Research
  2000 - 2002
  SAKAOKA Keiichiro; YONETA Kunisaburo; SHIGA Naonobu; MEGURO Toshimi; BOWER John; YAMAMOTO Jun
  Plankton nets have been used for as a method for collecting the plankton. Especially, the NORPAC-NET is widely used in order to keep the compatibility of the data and there are many long-term data based on the NORPAC samples. NORPAC-NET sampling is easy to operate, the wire angles often exceed 40 degrees when sea condition is rough. These would suggest that these samples were estimated over or less than the normal condition. Then, this study investigates the collection characteristic of the NORPAC net and the property of the long-term data set. Furthermore, the present study examines other plankton net, MTD-Net, Bongo-Net and the retention on the survey-net mesh.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, 12660158
• 練習船ＡＤＣＰデータの品質管理処理と迅速な海流情報提供システムの開発
  Competitive research funding
• 津軽暖流と親潮の係留観測
  Competitive research funding
• 高緯度海域におけるノルパックネット標準採集の特性-その2 荒天下に起こる過剰曳網とプランクトン現存量評価
  Competitive research funding
• Characteristics of standard methods of Norpac net Towing in the high latuliude sea area II.Overtowing under vough sea condirious and estimation of zooplankton abundance.
  Competitive research funding