Abstract
In order to grasp return process of brachyuran megalopae to the Amparu Tidal Lagoon, they were collected by using two planktonic nets at the channel connects with the Nagura Bay in Feb. to May, 2007. Many megalopae captured intensively for a short time during the flooding tide before dawn around the new moon periods of Mar. and Apr. Based on the results, the immigration region of megalopa in the sea is estimated, and it seems that they immigrate from the deeper area approximately 500 meters away from the mouth of the lagoon. The settlement distribution of them in the lagoon is examined by using the 2-D Lagrangean chasing simulation. The settlement distribution could be determined largely by not only flow field in this lagoon but also the timing of their return to the lagoon.
