| Agricultural channels can be important habitats for aquatic species inhabiting agricultural areas. However、 water supply in agricultural channels can vary substantially with types of agriculture and irrigation/drainage system、 and thereby affect the viability of local populations of aquatic species. In this study、 we focused on the amphidromous freshwater atyid shrimp Caridina leucosticta. To clarify whether C. leucosticta utilizes agricultural channels as a habitat in relation to fluctuations in the water supply、 we conducted a series of field surveys on the distribution of this shrimp in a rice paddy drainage channel (spring-fed channel) around the Furu River、 central Japan、 during July and December 2008. Large numbers of C. leucosticta had migrated into the drainage channel. Water from the adjacent rice paddies had disappeared by October because irrigation was stopped、 however the water level in the drainage channel was maintained by a supply of spring water. The supply of spring water by mid November had almost disappeared and then the channel nearly dried up、 and many shrimps were concentrated in an isolated water pool in the channel. Thus、 habitat fragmentation of C. leucosticta occurred in terms of water continuity. This water pool dried up completely by mid December. We found many dead individuals of C. leucosticta in the dried-up area of the channel. These results indicate that agricultural channels can be an important temporal habitat for amphidromous freshwater shrimps、 but that the drying-up of the channels can lethally affect atyid migrating shrimps. |
