Backwatered section and distribution range of medaka(Oryzias latipes) in irrigation and drainage canals of Kahokugata region [Ishikawa, Japan]
2004
Ichion, E. (Ishikawa Prefecture Coll. of Agriculture, Nonoichi (Japan)) | Ueda, T.
The distribution of medaka in irrigation and drainage canals was investigated. The investigation was conducted from spring to fall for three years in Uchihizumi area, Kahoku city, Ishikawa prefecture. Medaka began to expand its distribution from the downstream region to upstream at the water temperature above 20degC, and the distribution range was maximized in the mid-summer when the water temperature reached around 30degC. In the upstream region, medaka was distributed mainly in the section where velocity of water current was below 20 cm·ssup(-1). When irrigation was not being done, the fish restricted again its distribution range almost within the downstream region where velocity of water current was below 10cm·ssup(-1). The downstream region, which has stable water depths and low velocities of water current, was a main habitat of medaka during the survey period. It is considered that the region almost coincided with the section backwatered by West Drainage Catch of Kahokugata and to conserve the environment in the sections is significant for protecting medaka.
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