2020 年 26 巻 1 号 p. 11-23
Rokujo tidal flat called Rokujogata in the inner part of Mikawa Bay, is an estuary tidal flat developed at the mouth of the Toyo River. Juvenile Manila clams Ruditapes philippinarum larvae were caught there and then released to various places in Ise and Mikawa Bay, supporting the clam fishery. The authors focused on the feeding environment of juvenile clams as one of the causes of the mass outbreak. The appearance of phytoplankton in the coastal area around Rokujogata, which is used by these clams as food, was considered to be strongly affected by Toyo River, so we performed observations under various flood conditions. As a result, the relatively small size of chlorophyll a of 2–20 µm tended to increase under low salinity conditions around Rokujogata, and Cryptophyceae was considered to be important in its size. Cryptophyceae were suitable for feeding on juvenile clams because of their size, ecology, and food value, and their proliferation was thought to promote the mass outbreak of juvenile clams in Rokujogata.
