A rapid technique for recording sizes of juvenile pelecypod molluscs

Abstract

The production of the principal mariculture organisms started with the seaweeds in China rather than shrimp and fish. This is because the seaweeds are autotrophic and have relatively simple life histories whereas the shrimp and fish are heterotrophic and have complicated life histories. The mollusks are in the middle; they are heterotrophic but many of them are plankton feeders and have simple life histories. Thus, up to 1983, Japanese kelp still led in the mariculture production at 231 300 tons, and total seaweed production, at 241 300 tons, exceeded that of mollusks, at 239 000 tons of which 114 500 tons was mussels. We may well call this the “seaweed era” in Chinese mariculture. In 1986, however, mariculture of the mussel led the production, at 210 700 tons against 203 400 tons of Japanese kelp, and total mollusk production was 438 000 tons, occupying 51% of the total mariculture production. We are, therefore, in the “mollusk era” at present. Fish and shrimp should be the leading products of mariculture and this era will definitely come.In old China the seaweeds, mollusks, shrimp and fish were cultivated under traditional methods which were very inefficient, and in 1950 total production was only 10 000 tons. In the traditional methods, natural “seeds”, including spat and fry, were employed. These, however, were entirely at the mercy of nature. Artificial “seeds” were first employed in seaweeds. In 1952, the Japanese kelp, Laminaria japonica, was cultivated with sporelings grown from spores collected on artificial substrate. This was followed by the cultivation of purple laver, Porphyra spp. commercialized in 1963, mussels, Mytilus galloprovincialis, in 1972, the local scallop, Chlamys farreri, in 1973, the shrimp, Penaeus chinensis in 1979, and the bay scallop, Argopecten irradians, in 1985.