著者

笠井 久会 荒井 克俊

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.70, no.2, pp.113-118, 2020-12-23

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The student handbook (Gakubu-Annai or Gakusei-Binran) is distributed to all the freshman students in Hokkaido University at the first guidance class. This book provides various instructions on daily student life as well as general information for academic programs given by different undergraduate schools or faculties. In the chapter related to the Department of Fishing Science (DFS), Faculty of Fisheries, precondition sentence, female students are not suitable for DFS or similar sentences, was continuously found in the student handbook from 1980 to 1992. Such a statement presumably gave negative influence on female students, when choosing the undergraduate program to study. Although two female students graduated the department of Food Science and Technology, Faculty of Fisheries, for the first time in 1953, female students who graduated DFS first appeared in 1978. They decided to study fishing science despite the influence of the statement. Here, we examined the relationship between descriptions in the student handbook and percentages of female students in undergraduate and graduate programs of the Faculty of Fisheries Sciences, Hokkaido University.

著者

井黒 浩輔 今村 央

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.73, no.1, pp.27-32, 2023-08-04

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Three specimens of the birdbeak burrfish Cyclichthys orbicularis (Bloch, 1785) and a single specimen of the pelagic porcupine fish Diodon eydouxii Brissout de Barneville, 1846, collected from Usujiri, Hakodate, Hokkaido, Japan represent the first records from Hokkaido and northernmost records of both species. Together with Chilomycterus reticulatus (Linnaeus, 1758) and Diodon holocanthus (Linnaeus, 1758), diodontid species reported from Hokkaido. A single specimen, previously reported as a young individual of Ch. reticulatus, was reidentified as Cy. orbicularis.

著者

今井 圭理 渡邉 豊

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:13461842)

巻号頁・発行日

vol.65, no.2, pp.111-116, 2015-08-20

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Massive radioactive cesium was released to the North Pacific Ocean by the accident of the TEPCO Fukushima Dai-ichi Nuclear Power Plant from March 2011. Using the T/S "Oshoro-Maru" cruise, we started monitoring the concentration of radioactive cesium radioactive cesium(134Cs and 137Cs) in the North Pacific surface water from May 2011. Until December 2014, the samplings were carried out at 394 stations in the North Pacific Ocean including the Japan Sea and the Bering Sea. High concentration of radioactive cesium has been observed off Tohoku in 2011, and afterwards spread through the eastern side of the North Pacific by the Kuroshio Extension. In the most region, the radioactive cesium in the surface water reduced by less than the detection limit by the end of 2012. In order to clarify the spatiotemporal change of radioactive cesium in the ocean in future, the continuous monitoring by using the T/S "Oshoro-Maru" cruise be useful.

著者

三谷 曜子 岡崎 宏美 関口 圭子 宮下 和士

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:13461842)

巻号頁・発行日

vol.61, no.2-3, pp.65-74, 2011-12-26

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Killer whales Orcinus orca are cosmopolitan in distribution, but study sites are restricted to small geographic areas, primarily shore-based and boat-based studies focusing on nearshore areas. To contribute understanding about the biology of killer whales in pelagic areas, we created photographic identification catalogue of killer whales sighted during T/S Oshoro-maru cruise to the northern North Pacific, Bering Sea and Chukchi Sea in 2003, 2005-2009. For 6 years, 37 groups were found, containing 182 whales, and 29 individuals were identified from left side photos of dorsal fin. No individual was re-sighted within-year, nor between-year. And no matches were found between killer whales observed in Alaska, Russian far east seas, Kushiro and Shiretoko, Japan. Our result can serve as background information for the future study of pelagic killer whales.

著者

Hanamiya Yurika Murase Hiroto Matsuno Kohei Yamaguchi Atsushi

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.70, no.1, pp.77-89, 2020-08-24

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This study conducted diel vertical migration and active migration flux estimation of macrozooplanktonic amphipods and euphausiids at 0-250 m water column of the three stations in the western North Pacific during summer. For amphipods, 25 species belonging to 17 genera were identified. Their standing stock was 60-574 ind. m−2 during the daytime and 35-5,228 ind. m−2 at night-time. For euphausiids, 19 species belonging to 7 genera were identified. The standing stock of euphausiids was 80-382 ind. m−2 and 286-2,156 ind. m−2 during the day and at night, respectively. Feeding impacts during the night were estimated to be 0.19-11.76 mg C m−2 day−1 (amphipods) and 5.12-16.42 mg C m−2 day−1 (euphausiids). Respiration during the daytime accounted for 0.08-6.38 mg C m−2 day−1 (amphipods) and 2.33-7.70 mg C m−2 day−1 (euphausiids). The feeding impact and respiratory flux by active migration of macrozooplankton taxa were estimated as 8.34-28.18 mg C m−2 day−1 and 3.15-14.08 mg C m−2 day−1, respectively. These values corresponded to 3.7-12.4% of primary production (feeding impact) and 2.4-10.7% of sinking passive flux from the euphotic zone (respiratory flux). Thus, this study emphasizes the importance of active flux by macrozooplankton for vertical material flux in the western North Pacific.

著者

東 大聖 宗原 弘幸

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.71, no.2, pp.51-67, 2021-12-23

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We conducted SCUBA-based surveys of the larval and juvenile fish fauna in reef and seaweed areas in the inshore region of Usujiri, Hakodate, along the Pacific coast of southern Hokkaido, Japan, from 2019 to 2020. A total of 100 species in 10 orders and 44 families were identified based on morphological observations and DNA barcoding analyses of the cytochrome c oxidase subunit I (COI) gene. Of these species, two specimens of the labrid, Pseudolabrus sieboldi Mabuchi and Nakabo, 1997, one specimen of the cottid, Cottus hangiongensis Mori, 1930, two specimens of the blennid, Petroscirtes breviceps (Valenciennes, 1836), and one specimen of the gobiid, Pterogobius zacalles Jordan and Snyder, 1901, represent the first records of these four species in the study area. In addition, three specimens of the Stichaeid, Lumpenopsis pavlenkoi Soldatov, 1916, represent the first records captured during juvenile stages of this species, and one specimen of the pleuronectid, Lepidopsetta mochigarei (Snyder, 1911) represent the first juvenile captured in Usujiri of these species. The fish list is also added in this report.

著者

Yamaguchi Atsushi

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.71, no.1, pp.29-37, 2021-08-03

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Respiratory oxygen consumption rates (at the two temperatures of 0-50 m and 50-200 m depth strata) and day/night biomass in the top 50 m water column were determined on adult female Metridia pacifica at twelve stations in the western/ eastern subarctic Pacific and one station in the oceanic Bering Sea during summer. At each station, the respiration rates at 0-50 m depth temperatures were used to estimate ingestion rates during nighttime by assuming empirical carbon budget efficiencies, and rates at 50-200 m to estimate respiratory carbon flux during daytime. The abundance of the females in the upper 50 m at night varied between 27 and 5,422 inds. m−2 and no specimen was collected from the same layer at daytime throughout the stations. The size of the females varied regionally from 25 to 77 μg C ind.−1. As a result, diel vertical migrant biomass of the females varied greatly from one station to the next (1 and 309 mg C m−2). Weight-specific respiration rates of the females were 2.2-6.3 μl O2 mg C−1 h−1, which was a function of experiment temperatures and body mass (C) of the females. Taking into account of residence time at 0-50 m and 50-200 m in the day, daily population ingestion was estimated as 0.04-11.04 mg C m−2 day−1, which accounted for 0-2.4% of primary production at each station. Daily population respiration in the 50-200 m was calculated as 0.02-9.39 mg C m−2 day−1, which corresponds to 0-10% of the POC flux down from the euphotic zone.

著者

Abe Yoshiyuki Hildebrandt Nicole Matsuno Kohei Niehoff Barbara Yamaguchi Atsushi

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.70, no.1, pp.91-102, 2020-08-24

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We compared copepod abundance, biomass and community structure in the Atlantic sector (Fram Strait) and Pacific sector (Canada Basin) of the Arctic Ocean by using vertical stratified zooplankton samples collected from 0-1,000 m or 0-1,500 m during daytime in summer. Abundance and biomass were high at the surface layer and decreased with increasing depth in both regions. Abundance and biomass in the surface layer in the Fram Strait were 6-18 times higher than those in the Canada Basin. According to cluster analysis, the copepod communities were separated into three groups that varied vertically and included both locations. Regional differences were marked for Calanus finmarchicus, which was distributed only in the Fram Strait. In the Canada Basin, Spinocalanidae composed 56.1% of calanoid copepod abundance for the bathypelagic groups and also contributed 7.5% of abundance throughout the water column. The dominance of Spinocalanidae may reflect the oligotrophic environment in the Pacific sector of the Arctic Ocean.

著者

三宅 誠音 磯田 豊 今井 圭理 小熊 健治 澤田 光希

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.70, no.1, pp.1-11, 2020-08-24

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The shelf slope off Cape Erimo is very steep, and its slope width (L~30 km) is smaller than the internal radius deformation (λi~50 km). A simple model is used to investigate the dynamic response of Oyashio barotropic flow passing through this local steep slope area. Model results suggest that near-bottom Oyashio water cannot intrude from shelf area off Cape Erimo to Hidaka Trough, because inverse flow accompanied by the bottom trapped shelf wave is generated over the steep slope under the physical condition of L <λi. To confirm the existence of such inverse flow, hydrographic data at upstream and downstream both sides of shelf area off Cape Erimo were examined.

著者

泉 ひかり 萩原 聖士 玄 浩一郎 井尻 成保 足立 伸次

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:13461842)

巻号頁・発行日

vol.65, no.3, pp.125-130, 2015-12-20

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Removal of ribosomal RNAs(rRNA) from total RNA in eggs before preparation of a RNA library is required for the analysis of maternal mRNA using next-generarion sequencing ; this mRNA is essential for normal development. In mammals, the rRNA-depletion method is well-established and is already being used for the development of experiment kits. However, this method is not designed for other species, e.g., non-model organisms. In the current study, we attempted to remove rRNA from total RNA of Japanese eel Anguilla japonica, which is one of the most important aquaculture species in Japan. Removal was performed via hibridization-selection using mammalian probes from a commmercially available kit and/or an ordinally designed eel probe. Quantitative polymerase chain reaction(PCR) was performed to examine the depletion efficiency of 18S rRNA and 28S rRNA were comparative between each method, and >98% depletion was achieved. In addition, RNA-sequencing analysis using a next-generation sequencer and read-mapping analysis were carried out using the rRNA-depleted RNA, which was prepared using a mammalian probe, and mapping analysis revealed that rRNA reads were <1% of the total reads. These results suggest that an rRNA-depletion kit designed for a mammal can also be used for fish species.

著者

磯田 豊 荒巻 能史

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.70, no.2, pp.119-132, 2020-12-23

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Selecting the parameters to represent vertical distributions of potential temperature and carbon isotope of δ14C obtained over almost whole areas in the Japan Sea, the average age of deep circulation was calculated using vertical one dimensional multi-layered model. The model results suggest that the maximum age of 160 year appears near the depth of 2,000 m and a reasonable vertical diffusive coefficient is around 2 cm2s−1. A sinking volume transport to deep water below 1°C is estimated to be about 1.3 Sv (1 Sv = 106 m3s−1), which has the same order of magnitude as the inflow volume transport of the Tsushima Warm Current.

著者

Sugioka Rikuto Matsuno Kohei Takahashi Keigo D. Makabe Ryosuke Takahashi Kunio T. Moteki Masato Odate Tsuneo Yamaguchi Atsushi

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.71, no.1, pp.39-50, 2021-08-03

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Various zooplankton studies have been conducted in the Indian sector of the Southern Ocean, but studies investigating spatial changes in both meso- and macro-zooplankton populations are limited. To reveal the north-south change of the mesoand macro-zooplankton community structure and the population structure of large copepods, we investigated zooplankton communities collected by the Ocean Research Institute (ORI) net along the 110°E transect in the Indian sector of the Southern Ocean during the austral summer. The zooplankton abundance and biomass were high at the stations north of 60°S and was dominated by large copepods, especially Calanoides acutus. A cluster analysis identified four zooplankton community groups. The distribution pattern of the community groups is likely to be related to the frontal system. The population structure of the dominant species of C. acutus, Calanus propinquus and Rhincalanus gigas had a similar tendency ; early copepodite stages were abundant in the northern region, while late copepodite stages dominated in the southern region. The meridional changes in the population structure are explained by different reproduction periods in each region related to sea-ice melt timing.

著者

樋口 淳也 河合 俊郎 宇治 利樹 今井 圭理

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.71, no.1, pp.21-28, 2021-08-03

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Seven specimens of fishes and three specimens of crabs were collected with drifting algae by T/S Oshoro-maru from off the Pacific coast of Tohoku region, northern Japan. In fishes, a single specimen was identified as Histrio histrio (Linnaeus, 1758), five specimens as Oplegnathus punctatus (Temminck and Schlegel, 1844) and a single specimen as Stephanolepis cirrhifer (Temminck and Schlegel, 1850). In crabs, except a single specimen of megalopa, a single specimen was identified as Guinusia dentipes (De Haan, 1835) and a single specimen as Portunus (Portunus) sanguinolentus sanguinolentus (Herbst, 1783). Because previous northernmost records of P. (P.) sanguinolentus sanguinolentus were reported from Boso Peninsula in the Pacific Ocean and Akita Prefecture in the Sea of Japan, the present specimen represents the northernmost record of the species in the Pacific Ocean.

著者

Obata Kota Kawai Toshio Takatsu Tetsuya

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.71, no.1, pp.15-20, 2021-08-03

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The coloration of small individuals of Nozawa’s prickleback, Stichaeus nozawae is presented for the first time, based on a specimen (112 mm SL) collected by T/S Ushio-maru from the Funka Bay, Hokkaido. The specimen has obscure bands on dorsal, anal, caudal and pectoral fins. Although specimens of comparable sizes (57.4-168 mm SL) have obscure bands on these fins, most larger specimens (252-361 mm SL) have no bands on the caudal and pectoral fins. Most descriptions or images in previous studies, including the original description, were based on large specimens (220-450 mm SL), which have no bands on these fins. Thus, bands on caudal and pectoral fins of S. nozawae tend to disappear with growth

著者

Umezawa Ryuhei Urushibata Hirotaro Takahashi Eisuke Arai Katsutoshi Yamaha Etsuro

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.70, no.2, pp.133-144, 2020-12-23

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Production of sterile individuals is the key technique for surrogate propagation in teleosts. Sterile hybrids may be the ideal surrogate host when they do not generate their own germ cells in their gonads. Here, we attempted hybridization experiments between zebrafish (Danio rerio) and six closely related species (Danio albolineatus, Aphycypris chinensis, Hemigrammocypris rasborella, Opsariichthys platypus, Nipponocypris temminckii, N. sieboldii) and one remotely related species (Tanichthys albonubes). Intersubfamilial hybridizations in the family Cyprinidae resulted in the occurrence of inviable abnormal larvae with the two parental genomes, except for the T. albonubes x A. chinensis hybridization, in which normal larvae survived. Allotetraploidy and spontaneous gynogenetic diploidy were infrequently detected in T. albonubes x A. chinensis and D. albolineatus x A. chinensis, respectively

著者

Fujimoto Takafumi Fujimoto Suzu Murakami Masaru Yamaha Etsuro Arai Katsutoshi

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.70, no.1, pp.103-111, 2020-08-24

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Tetraploid strains are important sources of diploid gametes available for further expansion of ploidy manipulation. Although artificial induction of tetraploid strains has been attempted by inhibition of a mitotic cell division of zygotes using hydrostatic pressure or temperature treatments at the early developmental stage, successful examples of viable and fertile tetraploid fish were very rare. Because most resultant tetraploid progeny exhibited extremely high mortality. Natural tetraploid variants are considered another source of diploid gametes. In the present study, we tried to induce new strains of tetraploid, triploid and androgenetic diploid using diploid sperm of a tetraploid ginbuna (Japanese silver crucian carp Carassius auratus langsdorfii), which caught at the Jounuma lake, Gunma Prefecture, Japan. New tetraploids, i.e., neo-tetraploids were induced by fertilizing eggs of a diploid goldfish Carassius auratus auratus with diploid sperm of the tetraploid ginbuna, followed by heatshock (40°C for 45, 60 and 75 s) to inhibit the second polar body release at 5 min after fertilization. Although a small number of neo-tetraploid fish survived, we could not obtain any fertile gametes from them in the present study. Triploids were successfully induced by fertilizing eggs of a diploid goldfish with diploid sperm of the tetraploid ginbuna. Some resultant triploid males produced aneuploid sperm at the age of maturation. Androgenetic diploids were induced by fertilizing UV-irradiated eggs of diploid goldfish with diploid sperm of the tetraploid ginbuna. A mature androgenetic diploid produced fertile haploid sperm.

著者

浅野 竜太 磯田 豊 小林 直人 中村 知裕 伊藤 薫

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.70, no.1, pp.63-76, 2020-08-24

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A new type of mechanism for the generation of vertical circulation is revealed with the use of numerical experiments for the bended channel model. In the steady passage-flow experiment with a flat bottom and no bottom friction, a remarkable vertical circulation is formed only at the downside of bended corner where a negative horizontal shear flow dominates. Specifically, we call this type circulation “Negative Shear induced Vertical Circulation (NSVC)”, which is caused through the dynamical unbalance of gradient flow and the vorticity balance between the lateral vorticity advection and the sea surface divergence. A field observation was carried out around the Ooma-zaki area in the eastern Tsugaru Strait to confirm an enhanced downward flow expected by the realistic experiment including the bottom slope and friction. The spatial istributions of water temperature support the existence of this downward motion.

著者

堀尾 一樹 磯田 豊 小林 直人 千葉 彩

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.70, no.1, pp.41-62, 2020-08-24

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If there is the coastal upwelling, it is common to think that the upward advection of cold deep water will make the coastal side cooler than the offshore side. Shelf slope upwelling (SSU) presented in this study, however, occurs only when the shallow coastal side is rather warm due to a continuous sea surface heating in summer. The present study investigated the formation process of such SSU using a numerical model driven by surface heating. From the results of examining unsteady state of heat budget and dynamic balance, SSU was found to be a kind of compensation flow, not the bottom Ekman flow. That is, to satisfy continuity in a vertical section, the offshore flow caused by the horizontal density/temperature gradient was supplemented by the shoreward flow strongly confined to the sloping seabed. This SSU will probably be one of the important flows contributing to material transport, e.g., unused nutrients and anoxic water etc., from deep to near coast in summer, while it is difficult to prove the existence of SSU even indirectly from the observed water temperature.

著者

Fang Xiaorong Isoda Yutaka

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.70, no.1, pp.25-40, 2020-08-24

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A multi-layered numerical model driven by seasonal change in sea surface heat flux with excess cooling was used to investigate the dynamics of a cooling induced current (CIC) in the Japan Sea. The original idea of the CIC was proposed by Isoda (1999) (Journal of Oceanography, 55, 585-596) as follows : eastward thermal flow in the interior region, i.e., Tsushima Warm Current (TWC), accompanied with meridional thermal gradient on the planetary-β plane would be determined by the heat balance between net heat loss at the sea surface and lateral heat transport from the southern entrance into the Japan Sea. The CIC model produced a significant meandering TWC with an east-west wave number of three, based on the property of a standing Rossby wave, only under the model condition that coexisted with seasonal disturbances of heat. A positive heat supply from the southern entrance to the Japan Sea occurred in late winter, extended slowly to the TWC region as the offshore advection of meandering patchiness in summer, and then contributed to the heat loss by sea surface cooling in the following winter. The whole TWC region was cooled not only at the sea surface in winter, but also by eastward advection of upwelled cold waters originating from the western boundary area in summer to autumn. The meandering flow was stably confined to the southern part because of the dominant southward eddy momentum fluxes, which were caused by the northwest-southeast inclinations of meandering ridge-axes. Owing to such seasonal change in the lateral transports of momentum and heat, the meandering TWC (or CIC) flow pattern was maintained as a “dynamic equilibrium state”.

著者

Matsuura Hiromi Isoda Yutaka

出版者

北海道大学大学院水産科学研究院

雑誌

北海道大学水産科学研究彙報 (ISSN:24353353)

巻号頁・発行日

vol.70, no.1, pp.13-23, 2020-08-24

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We examine the reason why non-equilibrium response of lunar fortnightly tide, i.e., Mf tide with 13.7-day period, dominates in the Japan/East Sea including the Tsugaru Strait. In the present study, tides combining with passage-flow through the (Tsugaru) Strait are numerically simulated with a two-dimensional form of hydrodynamic model. It has been known that nonlinear interaction of dominant diurnal constituents K1 and O1 results in new oscillation with the same period of Mf tide. Analysis of computed sea level and currents is aimed primarily at describing the enhanced currents and patterns of energy flow in the Strait. Next, the focus of our model study is investigation of mechanisms of pseudo-fortnightly current enhancement where passage-flow interacts with diurnal current variations, resulting in temporal change in the friction due to “form drag”. Thus, we combine the study for form drag of passage-flow with the hydrodynamic interactions of diurnal tidal currents to provide some insight into the locally generated fortnightly tidal forcing within the Strait.