Abstract
We examined the habitat status of aquatic animals within an ill-drained paddy field and an adjacent side ditch in Shiga, Japan, from March to November. A comparison of fauna throughout the season revealed that aquatic species were richer in the paddy than in the side ditch. Specifically, both anuran tadpoles and aquatic insects (Odonata, Hemiptera, and Coleoptera) were abundant in the paddy, indicating that the paddy environment offers low predation pressure and an abundant food supply, respectively, to these species. In contrast, stream-dwelling aquatic animals (Semisulcaspira libertina and Geothelphusa dehaani) were more abundant in the side ditch than in the paddy. Thus, both the paddy and the side ditch contributed to the conservation of a greater variety of aquatic animal species in ill-drained paddy fields. We then compared the fauna between the cropping and non-cropping season. A number of permanent-water species, such as Misgurnus anguillicaudatus, Cynops pyrrhogaster, and aquatic insects, were captured in the paddy during both seasons, presumably due to the presence of areas of permanent water remaining in the paddy even during the non-cropping season. These waters may have served as refugia habitats and overwintering sites for many aquatic animal species.
