Natural spat collecting in the pacific oystercrassostrea gigas(thunberg)

The oyster cultivation industry of Hiroshima has a history of nearly 400 years and provides about 70% of the oyster production for the whole of Japan. The favourable location enables all the spat to be produced locally and the number of collector plates used for this purpose each year reaches 200–300 million. The natural system of spat collecting which is operated at Hiroshima is explained here in detail. In the first half, the spawning methods, primary environmental factors, development, early life history, the fundamentals of larval development and ecology, resistance of the larvae to their environment, conditions for attachment of the larvae, larval growth and decline, etc. are discussed in detail. In the second half, the practical and technical facts concerning setting up forecasts of spat production, the appropriate number of collector plates for spat collection, the growth and decline of juvenile attached oysters are presented.