2020 年 26 巻 1 号 p. 25-34
In order to ascertain the size and phytoplankton group of the food that the settled juvenile and the early juvenile of the Manila clam Ruditapes philippinarum ingest in the sea area, Manila clams of each growth stage were bred in natural seawater collected in Mikawa Bay through laboratory experiments. Changes in size-fractionated chlorophyll a content and phytoplankton composition were investigated. The experimental results show that the settled juvenile ingested cyanobacteria and nanoflagellates such as Cryptophyceae less than 10 µm, the early juvenile ingested diatoms less than 20 µm in addition to nanoflagellates, and that the juvenile clam further ingested the diatoms and dinoflagellates size to 20 µm or more. The food environment is very important for the growth and survival of juvenile Manila clams. It is necessary to understand the size composition of the phytoplankton to evaluate the quality of food environment to these clams.
