Shigehiko Urawa
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View article: Production Trend of Hokkaido Chum Salmon Estimated by Multivariable Models Incorporating Environmental Factors and Biological Interactions in the North Pacific Ocean
Production Trend of Hokkaido Chum Salmon Estimated by Multivariable Models Incorporating Environmental Factors and Biological Interactions in the North Pacific Ocean Open
Global warming continues unabated. The global annual mean of sea surface temperature (SST) is increasing at a rate of 0.6ºC per century, and was the highest on record in 2023. SST in the North Pacific Ocean has warmed by about 1ºC over the…
View article: The Role of Parasitic Pathogens in the Population Dynamics of Anadromous Salmonids in the North Pacific and North Atlantic Oceans: A Review
The Role of Parasitic Pathogens in the Population Dynamics of Anadromous Salmonids in the North Pacific and North Atlantic Oceans: A Review Open
Numerous parasite species have been recorded from anadromous salmonids in the North Pacific and North Atlantic oceans, and they occasionally play a significant role in regulating wild fish populations. This paper focuses on three types of …
View article: PCR-based Discrimination and Scanning Electron Microscopy of Genotypically Differentiated Ectoparasitic Flagellates <i>Ichthyobodo</i> spp. Infecting Salmonid Species Cultured in Freshwater in Hokkaido, Japan
PCR-based Discrimination and Scanning Electron Microscopy of Genotypically Differentiated Ectoparasitic Flagellates <i>Ichthyobodo</i> spp. Infecting Salmonid Species Cultured in Freshwater in Hokkaido, Japan Open
The present study investigated the genotype of Ichthyobodo spp. that caused six cases of ichthyobodosis in various salmonid species cultured in freshwater, in Hokkaido, Japan, through molecular phylogenetic analysis of the parasite ribosom…
View article: Occurrence of <i>Salmincola edwardsii</i> (Olsson, 1869) and <i>Salmincola markewitschi</i> Shedko & Shedko, 2002 (Copepoda: Lernaeopodidae) on stream-dwelling salmonids in eastern Hokkaido, Japan, with observations on the morphology of the copepods
Occurrence of <i>Salmincola edwardsii</i> (Olsson, 1869) and <i>Salmincola markewitschi</i> Shedko & Shedko, 2002 (Copepoda: Lernaeopodidae) on stream-dwelling salmonids in eastern Hokkaido, Japan, with observations on the morphology of the copepods Open
Two copepod parasites, Salmincola edwardsii (Olsson, 1869) and S. markewitschi Shedko & Shedko, 2002, were collected from salmonids in eastern Hokkaido, Japan: these copepods were taken from whitespotted char, Salvelinus leucomaenis (Palla…
View article: Winter Ecology of British Columbia Chum Salmon in the Gulf of Alaska
Winter Ecology of British Columbia Chum Salmon in the Gulf of Alaska Open
There were relatively low abundances of ocean age 2, 3 and 4 chum salmon from British Columbia in the catches in the 2019 and 2020 Gulf of Alaska expeditions that possibly were an index of the poor adult returns in 2019 and 2020.Catches of…
View article: Quantitative Analysis of Diplomonad Flagellate <i>Spironucleus salmonis</i> Infection in Intestines of Hatchery and Wild Salmonid Fishes in Hokkaido
Quantitative Analysis of Diplomonad Flagellate <i>Spironucleus salmonis</i> Infection in Intestines of Hatchery and Wild Salmonid Fishes in Hokkaido Open
Diplomonad flagellate Spironucleus salmonis infection in hatchery-reared juvenile chum salmon Oncorhynchus keta and masu salmon O. masou has been previously reported in Hokkaido, northern Japan. We established a quantitative real-time PCR…
View article: Ultrastructural and Molecular Phylogenetic Identification of the Diplomonad Flagellate <i>Spironucleus salmonis</i> Infecting Hatchery-reared Salmonid Fishes in Hokkaido
Ultrastructural and Molecular Phylogenetic Identification of the Diplomonad Flagellate <i>Spironucleus salmonis</i> Infecting Hatchery-reared Salmonid Fishes in Hokkaido Open
Systemic infections caused by diplomonad flagellates belonging to the genus Spironucleus commonly result in heavy mortalities in salmonids. Diplomonad flagellates were found in the intestinal lumen of hatchery-reared juvenile chum Oncorhy…
View article: Long-term Shifts of Chum Salmon (Oncorhynchus keta) Distribution in the North Pacific and the Arctic Ocean in Summer 1982–2017
Long-term Shifts of Chum Salmon (Oncorhynchus keta) Distribution in the North Pacific and the Arctic Ocean in Summer 1982–2017 Open
Chum salmon (Oncorhynchus keta) is widely distributed in the North Pacific Ocean and adjacent waters.The thermal limit of chum salmon habitats is between 2.7℃ to 15.6℃ (Azumaya et al. 2007).Azumaya et al. (2007), Kaeriyama (2008) and Kaeri…
View article: Experimental evidence on prevention of infection by the ectoparasitic protozoans <i>Ichthyobodo salmonis</i> and <i>Trichodina truttae</i> in juvenile chum salmon using ultraviolet disinfection of rearing water
Experimental evidence on prevention of infection by the ectoparasitic protozoans <i>Ichthyobodo salmonis</i> and <i>Trichodina truttae</i> in juvenile chum salmon using ultraviolet disinfection of rearing water Open
In northern Japan, juvenile chum salmon Oncorhynchus keta (Walbaum) are released from hatcheries to enhance the fishery resource. Infections with ectoparasitic protozoans, particularly the flagellate Ichthyobodo salmonis and the ciliate Tr…
View article: Geographical Origins of Juvenile Chum Salmon Migrating Along the Pacific Coastof Hokkaido, Japan, During Early Summer
Geographical Origins of Juvenile Chum Salmon Migrating Along the Pacific Coastof Hokkaido, Japan, During Early Summer Open
Japanese chum salmon migrate globally, from their natal river to the Gulf of Alaska via Okhotsk Sea, Northwest Pacific Ocean, and Bering Sea depending on their life stage and season (Urawa 2004; Urawa et al. 2018).Irie (1990) illustrated a…
View article: First Records of Tracheliastes sachalinensis (Copepoda: Lernaeopodidae), a Fin Parasite of Cyprinids, from Japan
First Records of Tracheliastes sachalinensis (Copepoda: Lernaeopodidae), a Fin Parasite of Cyprinids, from Japan Open
Nagasawa, Kazuya, Urawa, Shigehiko (2017): First Records of Tracheliastes sachalinensis (Copepoda: Lernaeopodidae), a Fin Parasite of Cyprinids, from Japan. Species Diversity 22: 167-173, DOI: 10.12782/sd.22_167
View article: Epizootiology of the ectoparasitic protozoans Ichthyobodo salmonis and Trichodina truttae on wild chum salmon Oncorhynchus keta
Epizootiology of the ectoparasitic protozoans Ichthyobodo salmonis and Trichodina truttae on wild chum salmon Oncorhynchus keta Open
Infestations of the ectoparasitic flagellate Ichthyobodo salmonis and the ciliate Trichodina truttae have caused acute mortalities of hatchery-reared juvenile chum salmon Oncorhynchus keta in Hokkaido, northern Japan. This study examined t…
View article: First Records of <i>Tracheliastes sachalinensis</i> (Copepoda: Lernaeopodidae), a Fin Parasite of Cyprinids, from Japan
First Records of <i>Tracheliastes sachalinensis</i> (Copepoda: Lernaeopodidae), a Fin Parasite of Cyprinids, from Japan Open
The lernaeopodid copepod Tracheliastes sachalinensis Markevich, 1936 was found on the fins of three species of the subfamily Leuciscinae Bonaparte, 1846 (Cypriniformes: Cyprinidae): big-scaled redfin, Tribolodon hakonensis (Günther, 1877);…