Author(s): K. Uno; S. Nakano
Linked Author(s):
Keywords: Salinity; Genus Uca; River mouth; Larval release; Lagragean Analysis
Abstract: The ecology of animals on tidal flats is closely linked to the salinity environment around a river mouth. In particular, salinity is the most influential environmental factor for habitats of organisms' larval stage. However, until the present, much information about larval stage of tidal flat's animals still remains unknown. In this study, the relationship between salinity environment and behavior and habitat of the larvae of genus Uca, which is now in danger of extinction in Japan, was examined through laboratory experiments, field observations and numerical simulations. The study site was the mouth of the Yoshino River, Shikoku, Japan. Bars and tidal flats around this river-mouth are precious habitats for genus Uca. In this study, first, to clarify the larvae's preference for salinity, laboratory experiments were carried out. Secondly, the relationship between topographic distribution of Uca's larvae and salinity at the Yoshino river-mouth were investigated by field observation. Finally, movement of larvae from hatching to 10 days after was calculated using semi 3-D tidal current and Lagragean Analysis. The results are summarized as follows: 1) Larvae of genus Uca prefer high salinity of more than 20 psu. 2) The habitat distribution of larvae at the Yoshino river-mouth is limited until 5km upstream and they were found in the bottom layer which has high salt concentration. 3) The results of larval movement simulation coincides with that of field observations. It was apparent that 90% of larvae die within 1 week after hatching and most of surviving larvae stay around their original tidal flat.
Year: 2003