| Sea urchin Anthocidaris crassispina(A. Agassiz), one of the important fishery species in the sea of southeast China, is of great nutritional value. Owning to the rapid decrease in A. crassispina stocks in several years, it is urgent to take some actions to change this situation, such as releasing and enhancing. In order to protect and rational utilize fishery resources, we studied several key technologies of releasing and enhancing. 296 ind A.crassispina were collected in west of Guangxi province, Fujian province and Guangdong province and other coastal areas. Population discrimination is the necessary step in releasing and enhancing. In addition, it is helpful to forecast the trend of fish stocks.We researched the relationship and genetic structure among groups by means of the morphological characteristics and DNA sequence analysis. In order to study the growing state of juvenile A. crassispina after released in the waters, we designed several experiments in Dayawan Bay to simulate the naturally growing environment in the sea for 8 months. The main contents and results of this papwr are as follows:(1)Research of population discriminant based on morphological variationsIn order to study the morphological variations in A. crassispina populations, six groups collected from Southeast China Sea--- 47 from Daya Bay, 51 A.crassispina from Egong Bay, 50 from Hailing Island,48 from Nan’ao Island, 50 from Weizhou Island in Guangxi province and 50 from Ningde city in Fujian province were analyzed. Six morphometric traits were measured from A.crassispina and the degree of morphological variation among groups was calculated using four multivariate analyses. The result of one-way ANOVY indicates that six morphometric traits of the Weizhou-Island population is significant different from other five groups. Coefficient of Difference Analysis shows that the difference between Weizhou-Island population and Hailing-Island population reaches the interspecific level. Cluster analysis shows that the morphometric characters of the Daya-bay population, Egong-bay population and Nan’ao population are more similar to the Hailing population. The most divergent groups are those groups of Ningde and Weizhou Island. Discriminant analysis results indicate that the identification accuracy of A.crassispina is 47.8%~86%. The total discriminant accuracy is 65.3%. All results support that there are some differences among A.crassispinagroups on morphological characters.The different groups of parents A.crassispina can be distinguished by discriminant equations and morphological data. Thereby, it can be judged if juvenile A.crassispina are suitable for enhancing in the sea.(2)Research of population discriminant based on genetic variationsThe COI sequences of six groups collected from Daya Bay, Egong Bay, Hailing Island and Nan’ao Island in Guangdong province, Weizhou Island in Guangxi province and Ningde city in Fujian province were analyzed.The result shows that in 772 bp base-pair sequences there are 93 mutations and 89 haplotypes. It indicatesthat the A.crassispina have abundant polymorphism, high genetic diversity and environmental adaptability. The average genetic distance are 0.001052~0.001686 for A. crassispina between groups, and 0.005406~0.007649 within groups. The haplotype diversity of all groups are high,otherwise the nucleotide diversity are relatively low. The median-joining network and phylogenetic tree show no phylogeographic differentiation structure in 6 wild groups.All results indicate that there is no genetic differentiation between groups. The similarity of the COI sequences of six groups is high, so they cannot be distinguished by this sequence. The method of population discriminant based on genetic variationsshould be further studied.Morphological analysis shows that there are some differences among A.crassispinagroups, but analysis of molecular biology shows not. It means the morphological difference come from environment and have not reached the genetic level. But weather releasing and enhancing affects the wild genetic structure of A.crassispina of different groups should be further studied.(3)Growth of juvenile A. crassispinareleased and enhanced in Dayawan BayIn order to study the growing state of juvenile A. crassispina after released in the waters, we designed several experiments in Dayawan Bay to simulate the naturally growing environment in the sea for 8 months. Juvenile A. crassispina have been divided into 3 groups according to the diameter of shells and each group had 5 number density gradients. The diameter of shells was between 3 mm and 9mm,the number density was between 3 ind and 25 ind per experimental facility(the superficial area of experimental facilities was 0.473m2), and the weight density was between 1.48 ~13.32g/m2. Theresult indicates that the diameter of shells and number density affect the death rate significantly. At the beginning, there is a significant difference in Growth rate of Shell Diameter(GSD), Special Growth Rate of Shell Diameter(SGR) and Net Yield of Shell Diameter(NY) between different number density gradients. 2 months later, this difference disappears. There is also a significant difference in production between different weight densities. When the weight density is 10g/m2, the production is the highest. From the November to the March in next year, the juvenile A. crassispina grow more slowly and the Growth rate of Shell Diameter(GSD) is smaller.In this paper, densitiy affects the growth of juvenile A. crassispina. High densitiy leads to high death rate, low Growth rate of Shell Diameter, low Special Growth Rate of Shell Diameter, low Net Yield of Shell Diameter and low weight growth rate. In the density range of this paper( the number density is between 6~52 ind/m2,the weight density is between 1.48~13.32 g/m2),the most suitable number density which shell diameter is 3~5mm,5~7mm,7~9mm is 31 ind/m2,17 ind/m2and6 ind/m2. The most suitable weight density is between 6 g/m2 ~ 10 g/m2. In order to get the high survival rate, the shell diameter of juvenile A. crassispina should be bigger than 5mm. |
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