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Eniwa, Japan

Shimoda K.,Hokkaido Fish Hatchery | Shimoda K.,Salmon and Freshwater Fisheries Research Institute | Nagasaka A.,Hokkaido Forestry Research Institute | Nagasaka A.,Forestry Research Institute | And 2 more authors.
Ecology and Civil Engineering | Year: 2014

Relationships between land use and the carbon and nitrogen stable isotope ratio of riparian plants, aquatic algae and masu salmon juveniles of seven rivers in the coastal area of Ishikari Bay Hokkaido, Japan were examined. Principal component analysis was conducted to characterize the land use of these rivers. The correlation between the principal component scores and the stable isotope ratio of riparian plants, aquatic algae and masu salmon juveniles in these rivers was analyzed. The first principal component (PC1) accounted for 47∼57% of the variance of land use variables. Component loadings of PC1 were positive high in the land use of agricultural land or artificial forest, and were negative high in the land use of natural forest and natural grassland. A positive correlation was observed between the principal component scores of PC1 and the nitrogen isotope ratio of aquatic algae and masu salmon juveniles. These results suggest that the nitrogen stable isotope ratios of aquatic algae and masu salmon juveniles are influenced by land use. These stable isotope ratios provide a useful index of the human impact on stream ecosystems. Source


Arias-Rodriguez L.,Hokkaido University | Yasui G.S.,Hokkaido University | Kusuda S.,Hokkaido Fish Hatchery | Arai K.,Hokkaido University
Journal of Applied Ichthyology | Year: 2010

Reproductive capacity was analyzed in inter-populational hybrid males between geographically different populations of the loach Misgurnus anguillicaudatus, which were suggested to be genetically distinct by previous studies. Hybrid males exhibited high percentages of spermatozoa with poor or no motility, when compared with wild type diploid males. Sperm volume was apparently less than that from wild type. Scanning electron microscopy (SEM) revealed that spermatozoa of hybrid males showed abnormal morphology such as no flagellum, double or more flagella, ill-developed mid-piece and significantly larger head sizes. Three different cell populations with haploid (1C), diploid (2C) and tetraploid (4C) DNA content were flow-cytometrically detected in sperm samples collected from hybrid males, whereas diploid males showed only haploid spermatozoa. Fertilization of eggs of wild type females with sperm of hybrid males gave very few diploid and triploid survivors. Microsatellite analyses showed that haploid spermatozoa of hybrids were produced by meiotic segregation, while diploid spermatozoa were formed by unreduced spermatogenesis. The present results showed that inter-populational loach hybrid males were almost sterile, but a few fertile haploid and diploid spermatozoa were generated. Such traits of inter-populational hybrid males are similar to those reported in inter-specific hybrids. Hybridization disrupted regular meiosis and normal spermatogenesis in the loach from the cross between different populations. © 2010 Blackwell Verlag, Berlin. Source


Yu J.-N.,Hokkaido University | Azuma N.,Hokkaido University | Yoon M.,Bioscience Technology | Brykov V.,RAS A.V. Zhirmunsky Institute of Marine Biology | And 4 more authors.
Zoological Science | Year: 2010

The population genetic structure and phylogeography of masu salmon were investigated by using variation in the mitochondrial NADH dehydrogenase subunit 5 gene (ND5) and six polymorphic microsatellite loci among a total of 895 fish representing 18 populations collected from Japan (9), Russia (7), and Korea (2) from 2000 to 2008. An analysis of ND5 nucleotide sequences revealed 22 variable sites in about 560 bp in the 5′ half of the gene, which defined 20 haplotypes, including some associated with geographical regions. Haplotype and nucleotide diversities were greater in the populations in Japan and Korea than in those in Russia, indicating greater genetic diversity in the Japanese and Korean populations than in the Russian populations. All the microsatellite loci examined showed a high level of variation, but the expected heterozygosity indicated a similar level of genetic diversity among the populations of the three regions, contrary to the results for ND5. However, AMOVA and pairwise population F ST estimates for both ND5 and the microsatellite markers indicated a similar pattern of moderate genetic differentiation among populations of the three regions, and large population groups on the coasts of the Sea of Japan, Sea of Okhotsk, and Pacific Ocean in the Far East. From a mismatch distribution analysis and neutrality test, the observed genetic structure appears to have been influenced primarily by bottlenecks during glacial periods and population expansions during interglacial periods in the late Pleistocene. © 2010 Zoological Society of Japan. Source


Shimoda K.,Hokkaido Fish Hatchery | Shinriki Y.,Hokkaido Fish Hatchery | Kasugai K.,Hokkaido Central Fisheries Experiment Station | Hoshino N.,Hokkaido Fish Hatchery
Nippon Suisan Gakkaishi (Japanese Edition) | Year: 2010

The variation in morphological characteristics of adult pink salmon Oncorhynchus gorbuscha collected in nine rivers in Hokkaido, Japan was surveyed in 2005 and 2006. Results of the cluster analysis and discriminant analysis suggested that the difference in meristic counts between the years was greater than that among rivers. The difference in the numbers of dorsal fin rays, anal fin rays and vertebrae between years was greater than that among rivers within year. There was a significant difference in the count of pectoral fin rays and gill rakers of the specimens among rivers, but not between years. Principal component analysis revealed that the 2006 year fish have more dorsal fin rays, anal fin rays and vertebrae, than the 2005 year fish. Source

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