Study On Variation Of Fish Community Structure In Poyang Lake Channel In Summer And Autumn And The Otolith And Growth Of Juvenile Domestic Chinese Carps

Poyang Lake is a naturally fluctuating lake. As one of the three lakes maintaining a connection with the mainstream of Yangtze River, it is an important feeding ground of juvenile domestic Chinese carps. So far, the migration of larval domestic Chinese carps from Yangtze River to Poyang Lake has not been well studied. And the studies on the fish in Poyang Lake channel are very lacking.Based on the investigation data of fish community in the Poyang Lake channel, from June to October 2010, the dynamics of fish community and the migration of larval domestic Chinese carps from Yangtze River to Poyang Lake were studied. The daily ages and growths of the juvenile domestic Chinese carps were studied based on microstructure of lapillus. The main results were as follows:1. A total of 50 fish species belonging to 8 families 39 genus were found in the Poyang Lake channel. There were 32cyprinid fishes, accounting for 64.00% of the total fish species. Shannon-Wiener index(H') and Pielou's evenness index(J') were going higher from Hukou to Xinchi in the Poyang Lake channel. Margalef index(D) in xingzi was higher than that in xingchi, and in hukou it was lowest.2. In 2010, the date of the migration of larval domestic Chinese carps from Yangtze River to Poyang Lake occurred on June 26, the peak period of the migration ranged from middle of July to late August. The total number of the migratory larval domestic Chinese carps was estimated to be 3.1×106.In which, silver carps account for 78.75%, grass carps account for 18.43%, black craps account for 2.06% and bighead carps account for 0.76%.3. Based on daily growth increment of lapillus, the analysis showed that the daily ages of grass carps ranged from 45-79d, mean daily age was 65.9±7.1d; daily ages of black carps ranged from 53-95d, mean daily age was 78.1±10.8d; daily ages of silver carps ranged from 43-102d, mean daily age was 62.4±8.1;daily ages of bighead carps ranged from 51-93d,mean daily age was 70.9±10.5d.4. Short radius of lapillus and body length was linearly correlated, whereas exponential relationship was found between short radius of lapillus and body weight of juveniles.5. The growth model of body length and weight fitted exponential functions. The index in exponential model was approximately 3 indicating the growth of juvenile domestic Chinese carps was equally between body weight and body length.