Relationship Between Farm-Pond Drainage Frequency and Biota in Ueda, Japan

Abstract

Farm ponds, which have been used for irrigation for centuries in many areas of Japan, are one of the representative water environments in Satoyama. Compared with water bodies such as rivers and lakes, small water bodies such as ponds can support unique and sometimes rare biota. Conservation of this habitat is of great importance for conservation of regional biodiversity. However, irrigation use and pond management have declined over time with an aging farmer population and with changes to irrigation systems. Consequently, a pressing need exists to ensure ongoing pond maintenance and management. We investigate the effects of pond draining on biota at 26 ponds in Ueda City, Nagano Prefecture. The frequency of pond drainage is negatively related to numbers of species of fish and crustaceans, suggesting that cumulative effects of frequent pond draining prevents the community assembly. Bullfrog populations also tended to be smaller in more frequently drained ponds, suggesting that pond drying can control this exotic species.