Proposal of a Fish Habitat Environmental Model at Hill-bottom Valleys Waters In Tochgi Prefecture

概要

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Based on previous research results concerning environmental conditions of fish habitats in valleys of the Kokaigawa river basin, we propose a fish habitat environment model incorporating a three-scale micro-to-macro approach. To verify the generality of this model, investigative surveys were conducted at nine valleys in the Kokaigawa, Okawa, and Sakuragawa river basins. The results are as follows: 1) On the macro scale, a relatively high number of fish species are found in valleys that have large basins, deep canals, or a high rate of rice paddy fields. In valleys where water networks and deep canals have been constructed, habitats of the Numamutsu and Tamoroko species can be found. Furthermore, the number of fish species and habitat distribution is determined by particular attributes of water areas. 2) On the meso scale, habitat distribution and density are directly affected by environmental gradients. For example, water temperature affects Hotokedojo habitats and the cumulative height of dams affects Numamutsu habitats. 3) On the micro scale, the layout and structure of canals are factors that qualitatively affect habitat density. 4) Applying the habitat environment model, the findings suggest that the environmental conditions that affect habitat distribution have a stronger impact than those affecting habitat density.
公益社団法人農業農村工学会の論文