Effects of Habitat Fragmentation on the Amphidromous Freshwater Shrimp, Caridina Leucosticta (Decapoda, Atyidae) in a Rice Paddy Drainage Channel

Abstract

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 that drainage channel. Water from the adjacent rice paddies had disappeared by October, because irrigation was stopped, but the water level in the drainage channel was maintained by a supply of spring water. By mid-November the supply of spring water had almost disappeared, 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 (dis-)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 migrating atyid shrimps. RÉSUMÉLes canaux agricoles peuvent être des habitats importants pour les espèces aquatiques rurales. Cependant l'alimentation en eau des canaux agricoles peut varier substantiellement avec le type 4 )

Factors affecting distribution of freshwater shrimps and prawns in the Hiwasa River, southern central Japan

“…In September and October, C. leucosticta accounted for nearly half of the roughly three hundred specimens collected in H03, but they were seldom collected in H04 (Saito et al, unpublished data), suggesting that their upstream migration is blocked by some physical barrier between these two stations. Nakata et al (2010) reported that C. leucosticta occurs in high density in the middle reaches of Toyokawa River, Aichi Prefecture, central Japan, which is roughly 20 km upstream of the river mouth. This result suggests that C. leucosticta is capable of migrating much longer distance upstream than what has been observed in the present study, if the gradient is gradual and vegetation continuously cover river bank.…”