An evaluation of the potential influence of SST and currents on the oceanic migration of juvenile and immature chum salmon (Oncorhynchus keta) by a simulation model     

Tomonori Azumaya  Yukimasa Ishida 《Fisheries Oceanography》2004,13(1):10-23

Using a salmon migration model based on the assumption that swimming orientation is temperature dependent, we investigated the determining factors of the migration of juvenile and immature chum salmon (Oncorhynchus keta) in the North Pacific. We compared the predictions of the model with catch data of immature and juvenile chum salmon collected by Japanese research vessels from 1972 to 1999. The salmon migration model reproduced the observed distributions of immature chum salmon and indicates that passive transport by wind‐driven and geostrophic currents plays an important role in the eastward migration of Asian salmon. These factors result in a non‐symmetric distribution of Asian and North American chum salmon in the open ocean. The directional swimming component contributes to the northward migration in summer. The model results indicate that during the first winter Asian chum salmon swim northward against the southward wind‐driven currents to stay in the western North Pacific. This suggests that Asian chum salmon require more energy to migrate than other stocks during the first winter of their ocean life.  相似文献   

Nonrandom distribution of chum salmon stocks in the Bering Sea and the North Pacific Ocean estimated using mitochondrial DNA microarray     

Shogo Moriya  Shunpei Sato  Moongeun Yoon  Tomonori Azumaya  Shigehiko Urawa  Akihisa Urano  Syuiti Abe 《Fisheries Science》2009,75(2):359-367

More than 1,000 age-identified chum salmon Oncorhynchus keta collected at 23 stations in the Bering Sea and the North Pacific Ocean in June to July 2003 were used to estimate their origin of stocks using a DNA microarray developed for analyzing the mitochondrial (mt)DNA haplotypes. The observed haplotype distribution was nearly the same as that reported previously for fish collected in September 2002 and 2003 in the present surveyed areas. A conditional maximum-likelihood method for estimation of stock compositions indicated that the Japanese stocks mainly distributed in north central Bering Sea, whereas the Russian stocks were mainly in western Bering Sea. The North American stocks were abundant in eastern Bering Sea and around the Aleutian Islands. Such an area-specific stock composition was not significantly different between mature and immature fish. Thus, the combined results of 2 years suggest that the distribution of chum salmon is nonrandom in the surveyed areas in summer and autumn, and that fish of the same origin migrate together to the same area irrespective of age.  相似文献   

Repeated reaching of the harmful algal bloom of Karenia spp. around the Pacific shoreline of Kushiro,eastern Hokkaido,Japan, during autumn 2021     

Hasegawa  Natsuki  Watanabe  Tsuyoshi  Unuma  Tatsuya  Yokota  Takashi  Izumida  Daisuke  Nakagawa  Toru  Kurokawa  Tadahide  Takagi  Satomi  Azumaya  Tomonori  Taniuchi  Yukiko  Kuroda  Hiroshi  Kitatsuji  Saho  Abe  Kazuo 《Fisheries Science》2022,88(6):787-803

Unprecedented large-scale algal blooms were observed during autumn 2021 around the Katsurakoi fishing port, Kushiro, eastern Hokkaido, Japan. Monitoring of shoreline water showed that chlorophyll a (Chl a) concentrations and the cell density of Karenia spp., dominated by Karenia selliformis, repeatedly increased synchronously between September and November 2021. These increases were associated with a southerly wind-driven current, which transported offshore water on the shelf towards the shoreline at the sea surface. The blooms were prolonged as a result of algal accumulation in the semi-closed fishing port. The maximum Chl a concentration and cell density exceeded 50 µg Chl a/L and 10⁴ cells/mL, respectively. During the autumn bloom of Karenia spp., the nitrate?+?nitrite and phosphate concentrations in the water were lower than those in 2019 and 2020, and the silicate concentration was comparable. The ammonium concentration during the bloom was notably higher than before the bloom period, reaching 15 µM. Mass mortality of several fish species and echinoderms that were cultured using rearing water intake from the same shoreline occurred synchronously with the increase in Karenia spp.

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Shift of NSF Funds     

Azumaya G  Brown A  Gilbert R  Lowengrub M  Masani P  Minty G  Rhoades BE  Sherman S  Tampfli J 《Science (New York, N.Y.)》1970,167(3926):1671

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A preliminary study to understand the transport process for the eggs and larvae of Japanese Pacific walleye pollock Theragra chalcogramma using particle-tracking experiments based on a high-resolution ocean model     

Hiroshi Kuroda  Daisuke Takahashi  Humio Mitsudera  Tomonori Azumaya  Takashi Setou 《Fisheries Science》2014,80(2):127-138

We developed a realistic 1/50° high-resolution ocean model capable of resolving submesoscale variability, and performed particle-tracking experiments based on this ocean model to identify elements that significantly affect the transport of the eggs and larvae of the Japanese Pacific walleye pollock Theragra chalcogramma into Funka Bay. The high-resolution model reproduced representative features of the oceanographic conditions of the main spawning area and season. A comparison of particle-tracking experiments performed under the passive transport condition based on high-resolution (1/50°) and low-resolution (1/10°) ocean models showed that high-resolution modeling is essential in order to realistically simulate the transport process. In this regard, however, the vertical motion of particles cannot be explained by the passive transport condition, as it leads to unrealistically deep sinking of particles in the simulation. Turning our attention to feasible non-passive transport conditions, we then incorporated the buoyancy motion of particles and conducted additional experiments that mainly differed in the particle density adopted. We clarified that buoyancy is an important factor in the retention of particles near the sea surface, and that the ratio of the particles that remain in Funka Bay to the number of particles released is sensitive to the vertical motions/positions of the particles, implying that it is necessary to model this vertical motion more accurately by incorporating more realistic biological processes or a statistical distribution into the particle-tracking model.  相似文献