This paper aims to propose concrete measures for the conservation of the mud loach (Misgurnus anguillicaudatus) in Sado Island of Japan, associated with the reintroduction of Japanese crested ibis (Nipponia nippon) that has a predilection to feed on the loach. The field survey was conducted at 80 sites on 7 rivers in the island in August 2007 and March 2008, in which the loach density and the micro-scale environmental factors (water depth [WD], degree of aquatic vegetation [AV], degree of riparian forest [RF], current velocity [CV], mud river bed [MB], concreted river bed [CB], and river bed pebble size [PS]) of the habitats were surveyed. Additionally, the macro-scale factors (paddy fields area [PA] and reservoirs area [RA] within a specific buffer circle) were also obtained using GIS software. The analysis using GLM and AIC showed that the AV (positive), MV (positive), CB (negative) and RA (positive), and AV (positive), MV (positive) and PA (positive) effect the loach density in August and March, respectively, indicating that the loach preferred the less artificial habitat surrounded by the paddy fields. The potential maps of the loach density were drawn by adapting the models on the rivers in the island: The loach density was especially high in the Kuninaka Plain that situated at central region of the island in both August and March, indicating the region was priority area for the conservation of the loach. In conclusion, removal of concrete revetment in the habitats and improvement of creek networks between rivers and landscape elements (paddy field and reservoirs) in the Kuninaka Plain would be the effective conservation measurements for the loach.
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