Life history of the amphidromous shrimp Caridina leucosticta (Decapoda: Caridea: Atyidae) in the Isazu River, Japan

The life cycle of a freshwater amphidromous shrimp Caridina leucosticta Stimpson, 1860 was studied in a temperate river from October 2005 to November 2006, including all aspects of its growth and reproduction, larval drift, distribution of developing larvae, and recruitment of developed juveniles. The growth rate of C. leucosticta was generally low when the water temperature decreased between October 2005 and April 2006. The growth rate then increased from April 2006 as the water temperature rose. Females grew faster and reached a larger body size at a given age than males. Brooding females occurred from June to September 2006. Larvae hatched in freshwater habitats were observed to flow downstream from July to October 2006, with a peak in July and August. Developing larvae were collected in September 2006, at two stations 0.6 and 2.0 km offshore from the river mouth, but were not found in the brackish estuary of the river. Developed juveniles were observed in the uppermost part of the brackish river estuary from August to November 2006. Juveniles were found in the freshwater habitat from October 2005 to April 2006 and from August to November 2006. Longevity was estimated to be 15-25 months. The life history of C. leucosticta as illustrated in the present study indicates that this species uses a broad range of habitats from fresh water to marine. Conservation measures should be considered for each habitat corresponding to each developmental stage and should also allow for connectivity between these habitats.