Study On Culture Techniques, Food Composition And Selected Breeding

Hyriopsis schlegelii originally distributed in Japan is a famous freshwater mussel, which is various species of the genus Hyriopsis cumingii which was original distributed in China. Since the successful natural propagation of first generation of H. schlegelii in 1998 which is fetched from Japan in 1997, three generations have been obtained by selective breeding in order to obtain improved characteristics about the more rapid growth, the better pearl performance and the stronger disease resistance. In this research, we focus on the culture technology, food species and selected breeding of H. schlegelii. For the purpose to provide some theoretical and practice instructions of freshwater pearl cultivation in our country, to work out the problem of unitary species of pearl clam, to promote a healthy and sustainable development of freshwater pearl cultivation.The pH value, transparency and temperature of the culture water was analysis from September 2006 to October 2007.The result indicated that the pH values varied from 6.0 to 7.5, the water temperature was 10℃in January and 30℃in mating season, the transparency was maintain at 40cm. The effects of rearing density of H. schlegeli showed that the best number for one year old H. schlegeli was 200 per cassette and 40 for two years old H. schlegeli.The feeding habits of one to four years old H. schlegeli was analyzed by the stomach and intestines content method. The results showed that the main foods of H. schlegeli were the green alga, the diatom, the bare algae, the blue-green alga, the organic detritus, and the largest relative feeding amount is between the end of the spring and the begin of sping, The results indicated the feeding amount of one year old mussel feed were few, only p. pyrum belong to genus phacus, Scenedesmus sp. and ankistudesmus sp. Which belong to genus chlorophyta, but feeding amount of three and four year old mussel feeds were bigger, the main foods were Scenedesmus, Crinalium, ankistudesmus sp. and Tetraedron Kuetz, which were belonged to family chlorophyta, and Navicula ,Synedra which were belonged to family Nitzschia Closterium.Four generations of the morphology and the growth were investigated, the results showing that compared with F2, the morphology of F3 was more suitable for culturing pearl and growing faster. Results indicated there was a trend that the descendants of selective breeding had the better capacity on growth and pearl performance.