抄録
The clam Ruditapes philippinarum (Adams) is one of Japan's most important fisheries resources; recently, however, the anuual catch of this clam has declined to less than one quarter of its previous maximum. In order to implement more effective management of this resource, studies on early life stages, particularly the recruitment process that regulates subsequent population dynamics, are essential. To date, the recruitment dynamics of R. Philippinarum have been poorly understood due to a lack of basic information resulting from difficulties in identifying the larvae. To remedy this lack, we studied the recruitment process of R. philippinarum from April, 1998, to March, 1999, in Mikawa Bay, central Japan, using a new monoclonal antibody method. Our study revealed that R. philippinarum produces larvae from April to November in Mikawa Bay, in two discrete periods. An early spawning period occurred from April to July, with the peak abundance of larvae moving from the north-west to the eastern part of the bay. A later spawning period was observed in a relatively limited season from August to November. The distribution of larvae was basically controlled by the current system of the bay, although the larvae tended to become dispersed as they matured. The new monoclonal antibody identification method, applied for the first time in a study of a natural population, was found to be useful for studying R. philippinarum. It also proved to be an effective procedure for rapidly processing a large number of samples.
