Abstract
Habitat suitability for medaka, Oryzias latipes, was predicted based on presence data for southern Ibaraki Prefecture, Japan, in the late 1960s. Land use on maps was used as an environmental variable for describing the niche of medaka. A multivariate analysis showed that the distribution of rice fields delineated the niche most strongly in a positive way. The distribution of urban areas was the second strongest variable, and also had a positive effect. Cropland, secondary grassland, and pine forest were also used in the niche description. A cross-validation test indicated that the prediction was reliable, as there was a significant correlation between the habitat suitability and the relative frequency of presence data among grids of each class of habitat. Given that a large area of rice fields has been altered, to allow mechanical cultivation, in such a way that medaka habitat has been destroyed, and the present distribution of medaka is limited and difficult to determine, the collection of such geographical information is encouraged in order to construct a present habitat suitability map for medaka.
