Fluctuation and variation in stream-fish assemblages after a catastrophic flood in the Miyagawa River,Japan |
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Authors: | Yuichi Kano Kaori Ohnishi Yasuo Tomida Naoyo Ikeda Naomi Iwawaki Masahiko Miyagawa Yasushi Harada Hidetaka Ichiyanagi Katsutoshi Watanabe |
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Institution: | (1) Department of Urban and Environmental Engineering, Graduate School of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819–0395, Japan;(2) Ohsugidani Nature School, 199 Kuzu, Ohdai-cho, Mie 519–2633, Japan;(3) National Salmon Resources Center, 2-2 Nakanoshima, Toyohira-ku, Sapporo, Hokkaido 062–0922, Japan;(4) Department of Bioresources, Mie University, 1577 Kurimamachiyacho, Tsu, Mie 514–8507, Japan;(5) Department of Zoology, Division of Biological Science, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606–8502, Japan |
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Abstract: | In the autumn of 2004, a typhoon caused a catastrophic flood of the Miyagawa River in Japan. Based upon snorkeling surveys
conducted every autumn from 2005 to 2009, we monitored the post flood fluctuation of the local fish assemblages at nine sites
of both the main stream and subsidiary streams of the river. Results revealed that species richness significantly increased
from 2005 to 2009. In addition, the fish densities of eight species significantly increased over the same period, whereas
the density of one species decreased, and that of eight others remained unchanged. Categorization based on Euclidean distance
revealed five main clusters from the nine sites. Among these sites, fish assemblages within subsidiary streams were stable
as they remained within the same clusters while those in the main stream were dynamically variable through time as they changed
cluster membership. In addition, the Euclidean distance between two arbitrary fish assemblages was positively correlated with
environmental distance (the Euclidean distance calculated based on river width, depth, velocity and pebble size), time distance,
and spatial distance along the river. In conclusion, the fish assemblages were dynamically and regularly altered and varied
in the five years after the flood, except for those in the subsidiary streams, and such variation was related to environmental,
temporal and spatial variation. |
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