Studies On The Techniques Of Artificial Reproduction Of The Crassostrea Sikamae And Cultivation Of The Cultchless Spat Of Crassostrea Gigas

Oyster, as a worldwide distribution of mollusca, has been a main breed in almost coastalstates,with tasty meat; nutrient rich and so on. With the confirmation of classification status,Kumamoto oyster (Crassostrea sikamea) in the wild started to be taken seriously in Japan,natural habitat, during recent years. The introduction of kumamoto oyster is not onlybeneficial to our half-shell market, but also can enrich the cultured oyster speciesis in ourcountry. While, Pacific oyster(Crassostrea gigas) has gained the biggest breed scale with thedevelopment of aquaculture. But the disadvantage of conventional breeding has slowed thesustainable development of oyster culture in our country. Free spats, as a kind of spats with noadhesion, will allow the production of uniform oysters both in shape and size and can beshipped in large numbers anywhere for relatively little cost, which can generate immenseeconomic value. According to the above, the techniques of artificial reproduction of theKumamoto oyster and cultivation of the cultchless spat of Pacific oyster had been studied.The main results are as follow:1. Artificial reproduction of the Kumamoto oyster.The conditioning of broodstock of Kumamoto oyster was conducted at26-27℃with thesalinity30. And then spawing and fertilization occurred. D-larvae appeared after17hours offertilization. The D-larvae developed to eye-spot stage in15th day when the tempereture wasaround28℃.The eye-spot larvae can settle on the scallop shell sucessfully and got themetamorphosis to be the spat. To avoid the more diseases and more other settling organismcaused by high tempereture, the spat were cultured in reservior temporarily. During thecultivation in the sea area, the spat growed slowly and had a high mortality with the salinity30. The optimum salinity for larval rearing was20. The highest growth rate and survival ratewere achieved with a mixed diet of Chlorella vulgaris and Isochrysis galbana at salinity20.The difference salinities and diets have significant impact on the growth rate and survival rateof larvae, and greater influence by salinity.2. Cultivation of the cultchless spat of Pacific oyster. The conditioning of broodstock of Pacific oyster was conducted for3months with thetempereture rising from10℃to20℃.At the end of May, the oysters got mature gonad andgot the zygote with artificial insemination.24hours later of fertilization, the D-larvaedeveloped and the rate of eye-spot larvae was80%at the16th day, when is the best time tothe larvae’s exposure to EPI. The rate of cultchless spat was90%with10-4M EPI, higher thanother concentrations. Besides the optimal concentration of EPI, the sifting of eye-spot larvaeswith synchronic development is evry important to improve the metamosphsis rate. Also, thedifferent concentrations of EPI didn’t influence the growth rate of spats.