Study On Biology Of Cynoglossus Semilaevis During Early Developmental Stage

In this dissertation, the biology of Cynoglossus semilaevis during early developmental stage were focused, the mainly areas are follows: study on early development of C.semilaevis; feeding habits and growth of larval,juvenile and young C.semilaevis; effects of temperature and salinity on growth and survival of juvenile,young C.semilaevis. The major obtained results were as follows:The morphological characteristics of early development of C.semilaevis were observed and described during October and December in 2010. The average total length of newly hatched larva was 2.73±0.211mm. At the water temperature of 18.1~24.8℃and the salinity of 33~34, the embryonic development took 4 days to develop into pre-larvae, and then took another 17 days to develop into post-larvae. The mouth could be seen in 3 days after hatching. The juvenile stage developed from 23 to 41 days after hatching. After 42 days, the fish developed into the early young fish period. Appear and disappear of crown-like fin, shift of right-eye and transformation of body coloring matter is the most obvious changes during early development of C.semilaevis. In addition, explore the differences of C.semilaevis and other flounder on morphological characteristics, and the dangerous period in the process of growth and development of larval, juvenile, young C.semilaevis.The ecological method was adopted to study the feeding habits and the growth of larval, juvenile and young C.semilaevis from December 2010 to February 2011. The results show that the larvae began to feed on the fourth day after hatching at water temperature of 18.1~24.8℃. The initial diet is rotifer. With the growth of larval, juvenile and young C.semilaevis, Artemia -nauplii could be fed in proper order. Based upon the determination of 190 individuals, the percentage of stomach with food was 94.6%, the plump coefficient of stomach was 1.1%~3.9%, and the dial feeding amount was 15.9%~33.5% of the body weight of larval, juvenile and young C.semilaevis. Rhythm of feeding intensity was obviously different during the day and night. The higher feeding intensity of larval fish was at 12:00 a.m and 18:00 p.m. Juvenile fish was at 9:00a.m~18:00 p.m. and that of young fish was at 18:00 p.m. and 24:00 p.m. Young fish fed also in the darkness of night,larval and juvenile seldom do. The time for feeding from empty to full in stomach, the average amount of food in full stomach, and the time for digesting food from full to empty in stomach by larval,juvenile and young C.semilaevis were determined in the present paper. The relationship between the feeding amount and body weight is expressed as y = 0.0165W + 0.0423, that of the total length and day age is LT = 2.666e0.0433D, that of the body weight and day age is W =0.747e0.117D, and that of the total length and body weight is calculated to be W = 0.0022LT3.276.The effects of temperature and salinity on growth and survival of young C.semilaevis were studied. The proper temperature of young young C.semilaevis range is16~28℃, the most suitable temperature range is16~24℃; Proper salinity degree range is 6~36, the most suitable salinity degree range is 6~30.The young C.semilaevis grow more fast, have more high survival rate under the proper temperature. Too high or too low temperature is not conducive to the growth and development of the young fish. In production, it should artificial elevate the temperature when the cultivate temperature was lower than 16℃. It has active signification to promote the young C.semilaevis growth and survival.