The Optimization Of Artificial Reproduction And Larvae Nursing Technologies On Anguilla Japonica

Anguilla japonica are catadromous fish, spawning in waters west of the Mariana Islands. Because of its special and complex breeding habits, their artificial breeding become a worldwide challenge, the larvae had been supplied by catching natural fish.However, due to the transition catching, the eel resources had been declined seriously recent years. Therefore, optimizing the artificial technology of eel reproduction is becoming particularly urgent and important.Through domestic and overseas research results about artificial reproduction of eels, as well as the eel life history of the survey recent years, this text had carried out the experiments about optimizing acceleration maturation and artificial breeding technology.Due to the basis of previous research, larval cultivation facilities were improved,designed to optimize artificially induced breeding techniques and the optimization of artificial seawater, Which can get the best water quality condition of embryonic development and provide basic data for the artificial reproduction of eels, the main results of this study are shown as follows:In order to explore the effect of different needle pitch and accumulated temperature on artificially maturation of eels, an experiment was conducted in the recirculatory system and in concrete pond, we measured and analyzed the injection by different conditions, Setting the accumulated time and Injection duration two-factor test test group. The accumulated time and Injection duration have a significant impact on the ripening rate of eel females, the ripening rate on a longer ripening period(every two weeks) and high accumulated temperature(> 1350 degree days) was higher than short periods(weekly one week) and low accumulated(> 1200 degree days).To assess the effect of different seawater on eel hatching and larval survival, an experiment about artificial seawater was conducted through detection of content in eel spawning. The redsea water was conducted by adding redsea on ultra-pure water, by sampling Da-yang-shan seawater from the ocean waters near the Da-yang hill. The results showed that: there was no significant difference in hatching rate of eels with the three seawater, but the larvaes in the redsea water died on the fourth day, eventuallyonly some larvaes in the artificial seawater reached the opening stage, indiating that artificial seawater was the best, which should be further optimized to breed the larvae to glass eel stage.Also the impacts of different Na+ and K+ concentrations and Na+/K+ ratio on the hatching rate of fertilized eggs, deformity rate of newly hatched larvae and survival time of larvae of Anguilla japonica were studied. There were three experiments: 1) to maintain normal Na+concentrations, while changing the concentration of K+; 2) to maintain normal K+ concentrations, while changing the concentration of Na+; and 3) to maintain stable Na+/K+at 28, while changing both Na+and K+concentrations. The results showed that: when the concentration of K+ was 538mg/L and Na+ 10760 mg/L,the highest hatching rate(44.0%) and lowest deformity rate(23.8%) as well as the longest survival time were achieved. When Na+ to K+ ratio was maintained at 28, with Na+and K+concentrations at 8400mg/L and 300mg/L respectively, the hatching rate was highest among the five groups. Hatching rates declined when the concentrations of Na+, K+were too high(19500mg/L and 1076mg/L respectively). These results indicated that appropriate Na+, K+ concentrations and R values are required with optimum Na+, K+concentrations varies between 7800~11700mg/L and 360~540mg/L respectively and R values 20~30.To hatch fertilized eggs and cultivate larvae effectively, this study designed a new farming system, a unique incubator structure had been designed, by setting a flooding water organization and pollution discharge organization, which can promptly remove the remaining bait and dead eggs, ensuring the quality of the water. Meanwhile,flooding water from the bottom can provide a smaller impulsion, maintaining a slower flow rate, and eel was suspended in water, which can avoid eel swimming to the bottom which cause jaw deformation. Also with setting the water injection organization and drainage channel can prevent the larvaes from dying because of own stream to the bottom wall of the body’s long stay eel suffocation from lack of oxygen-poor,meanwhile providing a better water environment. Besides, the bottom of the incubator with black dye, which is benefit for larvae feeding.