THE REPRODUCTIVE BIOLOGY OF FIRST FILIAL GENERATION OF ACIPENSER SINENSIS GROWING UP IN THE FRESHWATER ENVIRONMENT

Chinese sturgeon (Acipenser sinensis Gary) is an endangered anadromous species in the IUCN Red List. It was characterized as the national level key protected animal of China in 1988 and under the protection of CITES Appendix II in 1998. In order to realize the artificial propagation, mature Chinese sturgeons were captured below the Gezhouba Dam in the Yangtze River every year since 1982. And the induction of wild Chinese sturgeon succeeded in 1984. From then on, the artificially reproduced larvae of Chinese sturgeon were released every year. With the declining of the population, capture of wild Chinese sturgeon was prohibited by the government from 2008, so induction of cultured sturgeons was necessary to increase the quantity of larvae in the Yangtze River. From 1987 to 1997, many progenies of induced Chinese sturgeons captured from the Yangtze River were tried to culture in complete freshwater environment in Chinese sturgeon Institute. Twenty four growing-up individuals were selected for the attempts of the artificial propaga-tion study in 2006. We successfully made the gonads of these individuals develop into mature in freshwater environment via controlling culture environment temperature, lowering temperature to induce and supplying particular nutrient in 2009. The gonads were monitored by the combination of ultrasound detection and manual puncture detection. Primary biological data of egg, such as egg diameter and egg weight, the migration of the egg polar nucleus, were checked to confirm whether the female were mature and the microscope was used to check whether the male were mature. There were totally eight individuals whose gonads reached Phase III in 2008 and 2009. We found two mature brood fish (No. 6B7A and 391D) suitable to conduct artificial propagation via checking gonads in September 2009, and then we tried to conduct the first artificial induction in 29 September 2009, and part of the semen were Cryopreservation. In 22 November 2009, we confirmed that the gonad of a female (No. 3C67) was matured, and then we tried the second artificial induction. High quality sperm and eggs were obtained. Then we conducted the artificial insemination to the eggs of female No. 3C67 with the frozen semen of male No. 6B7A. To understand the reproductive biology of first filial generation of Chinese sturgeons growing up in the freshwater, individuals incubated from 1994 to 1999 were checked. The results indicated that the body size of individuals growing up in the freshwater was relatively small compared to the wild individuals. The egg diameter of these artificial cultured female individuals (4.540.12) mm and (4.560.19) mm was longer than wild groups (4.420.12) mm. The sperm quality of these individuals was higher (Sperm Swirling movement time was 60s; Sperm survival duration in normal temperature was 10min), and the fertilization rate and the hatchability of the ovum were also higher (71.4% and 64.3% respectively). Furthermore, 18,000 healthy second filial fries had been successfully cultivated. These results indicated that Chinese sturgeon could finish its reproductive cycle in completely freshwater environment.