Distribution of two sympatric amphidromous grazing fish Plecoglossus altivelis Temminck & Schlegel and Sicyopterus japonicus (Tanaka) along the course of a temperate river |
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Authors: | Shin-ichiro Abe Taiga Yodo Naoto Matsubara Kei’ichiro Iguchi |
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Affiliation: | (1) National Research Institute of Fisheries Science, Fisheries Research Agency, Komaki 1088, Ueda Nagano, 386-0031, Japan;(2) Department of Life Science, Faculty of Bioresources, Mie University, Kamihama 1515, Tsu Mie, 514-8507, Japan |
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Abstract: | Densities of two sympatric amphidromous grazing fishes, Plecoglossus altivelis and Sicyopterus japonicus, and gross primary production of benthic algae were investigated at the second, third and fourth-order sites located, respectively, 7.0, 6.7 and 3.6 km from the mouth of the Choshi River, Japan. Gross primary production estimated by multiplying gross photosynthetic rates by hours of insolation on the streambed increased downstream with decreasing canopy cover by valley walls and trees standing along the river. Density of P. altivelis was greatest at the fourth-order site with the higher primary production, while the distribution pattern of S. japonicus differed between adult (> ca. 7 cm in total length) and young individuals. Density of adult of S. japonicus was greater at the third-order site, although the young were more abundant at the fourth-order site. Aggressive acts against conspecifics and different species were observed only by adults of S. japonicus and most frequently observed at the third-order site. The upstream shift in the distribution of the adults of S. japonicus would mitigate interference competition with P. altivelis and contribute to their coexistence in the river. Handling editor: K. Martens |
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Keywords: | Amphidromous fish Distribution Coexistence Grazing Primary production |
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