Transplantation Technology of Big Silver Fish in Xingan, Inner Mongolia

Hangali Reservoir, located in Keerqin right-wing Middle Banner in the northeast of Inner Mongolia Autonomous region, is a medium-sized side reservoir on the Huolin River. In January 1996, 780000 fertilized eggs of Ctenopharyngodon idellus were transplanted from Luhun Reservoir in Henan Province and hatched naturally under the ice. Through the growth inspection in that year, it was found that the transplanted large silverfish grew and developed well, reached sexual maturity in late December, and began to reproduce naturally, achieving the first-class introduction effect. In January 1997, in order to consolidate the supplementary population, another 1 million fertilized eggs were released into the reservoir. By the time of trial fishing in September of that year, the fish had grown to 12-14cm. Because the reservoir had no fishing capacity and equipment at that time, it was contacted to hire a boat to fish from Taihu Lake in Jiangsu Province. The opportunity was delayed because of the long journey. That year, only the commercial big silver fish 370kg was caught. In the third year of transplantation, the production of large silverfish in Hangali Reservoir reached 24 tons, forming a fishery effect. After that, the output continued to rise, and by 2001 and 2002, the output was stable at more than 60 tons. In 2003, the reservoir was eliminated and strengthened, and the water storage capacity increased, and the output of the big silverfish reached 85 tons that year. In 2004, the big silverfish grew well and has now begun fishing, and the estimated output is still about 80 tons. Hangali has become a model for the successful transplantation of large silverfish in the northern reservoir.

Due to the successful transplantation of the big silverfish, the Hangali Reservoir has achieved great economic benefits. In view of the fact that the yield of large silverfish could not be stabilized after successful transplantation in many other waters of Inner Mongolia, and even disappeared by itself, we carried out a study on the high and stable yield technology of large silverfish in Hangali Reservoir. The specific situation is now reported as follows:

1. Take artificial measures to improve the productivity of water areas

1. Do a good job in the ecological construction in the reservoir basin area and maximize the potential of reservoir resources. Nine years of drought in Inner Mongolia has resulted in serious land desertification. Every year, a large amount of yellow sand blows into the reservoirs and channels with the wind, seriously eroding the reservoirs and channels. For this reason, the Hangali Reservoir Management Office has opened up a 100-hectare ecological reserve in the upper reaches of the reservoir, in which it is recommended to plant trees, prevent wind and fix sand, and conserve soil quality, so as to effectively protect the environment around the reservoir and improve the potential of reservoir resources.

2. Protect the water body from pollution and ensure the status of the pollution-free aquatic products production base of Hangali Reservoir. Hangali Reservoir is a side reservoir of Huolin River, there is no industrial area in the upper reaches, farmland is scarce, water quality is good, and it has favorable conditions for the production of pollution-free aquatic products. Big silverfish is the main kind of export earning foreign exchange of aquatic products in our region. After China's entry into WTO, China's economy is gradually in line with the world economy, and the quarantine and inspection system of aquatic products is becoming more and more perfect. Therefore, in order to maintain the long-term vitality of the big silverfish, we must do a good job in preventing pollution in the waters now. Hangali Reservoir is one of the first certified pollution-free aquatic product bases in our region. at present, bighead carp, carp and crucian carp have passed national certification and become pollution-free aquatic products, and other varieties are also being actively declared. The aquatic products of Hangali Reservoir have registered the trademark of "Silver ship" in the State Administration of Industry and Commerce.

3. Corresponding measures such as fertilization and regulation of water quality should be taken to improve the primary productivity of water bodies. From May to June, Hangali Reservoir used the surplus fertilizer from agricultural and pastoral areas to put fermented organic fertilizer in the key reservoir bay where the big silverfish is dense. First, it replenishes the nutrients in the water body, which provides a material basis for the reproduction of plankton in the reservoir; at the same time, a large number of organic detritus just make up for the lack of zooplankton in the water body in spring, providing a sufficient food basis for juvenile big silverfish. The exogenous nutrients brought into the reservoir are also an important source of nutrients in the reservoir. Increasing the water exchange capacity of the reservoir can increase the primary productivity of the reservoir, and then increase the output of the big silverfish in the reservoir.

Second, take artificial measures to create good living conditions for the big silverfish.

1. Reduce the enemy species of big silverfish. Because the large silverfish is small and its swimming ability is relatively weak, it is the target of ferocious fish in the middle and upper layers. Therefore, the impact of enemy populations must be reduced. The ferocious fish in the waters should be controlled below 5% in order to benefit the population development of the big silverfish. Hangali Reservoir has been in operation for more than 20 years, and there are more ferocious fish in the middle and upper layers, such as mackerel, meal sticks, Arroyo, red fin berth and so on. In order to create a good living environment for the big silverfish, in 1997, when it was too late to catch the big silverfish, we decisively changed to catch other wild and miscellaneous fish. In that year, more than three tons of wild and miscellaneous fish were caught; in 1998, more than five tons were caught, which fundamentally changed the fish structure of the reservoir, and the large silverfish quickly became the dominant population of fish in the Hangali Reservoir.

2. Reduce the number of low-value fish competing for food with big silverfish. Since the reform and opening up, the people's living standard has been greatly improved. People are no longer satisfied with the supply of low-grade aquatic products, and the traditional "four big fish" have been challenged. Because of its high protein content and delicious taste, the big silverfish is quickly accepted by people. Coupled with the influence of the international market, prices have soared all the way and become the darling of the market. The stocking capacity of silver carp and bighead carp in Hangali Reservoir has been insufficient, and there are no other fish with plankton as the main bait, so the bait of large silverfish is relatively abundant. However, in the future, the stocking amount of silver carp and bighead carp should be further controlled to provide a more adequate bait environment for large silverfish.

Third, take scientific measures to ensure the resources of big silverfish

1. Set up perennial protected areas. The population structure of large silverfish is simple, and 100% of the population is a supplementary population in the same year. Therefore, the number of supplementary populations has a direct impact on the fishery production of the year. Therefore, we must designate 5% of the water area in the reservoir as a perennial protected area. In the protected area, no fishing gear is allowed to fish at any time, making it a safe place for large silverfish to breed and live. In order to protect part of the large silverfish, continue to provide supplementary populations and multiply resources for the large silverfish population.

2. To determine the reasonable reserve of large silverfish resources. After the successful transplantation of large silverfish in Hangali Reservoir, we investigated the distribution, feeding habits and reproductive habits of large silverfish in the water. Conduct a resource assessment to determine a reasonable catch and retention. The main purpose of stipulating the catch is to ensure that sufficient reserves are retained. It can not only retain enough spawning parent fish, but also obtain higher fish yield at the same time. However, how to reasonably determine the reserve of large silverfish resources is a very difficult task. Our current practice is to stop fishing when the daily catch of a pair of tugboats is about 100kg, and take the remaining large silverfish as the reserve.

3. Set up a fish fence in front of the sluice to reduce the loss of large silverfish resources with the water. After several years of observation on the big silverfish, we did not find the phenomenon of upward tracing to the top water, but there was an escape phenomenon along the water, especially in the year with large water exchange capacity, the escape phenomenon was more serious. After 2000, in order to prevent the big silverfish from going down the river, we set up a dense-mesh fish fence in front of the outlet of the reservoir, which played a better role in preventing escape.

IV. Scientific management to prevent fish diseases

The prevention of fish disease in reservoir has always been more important than "cure". Big silverfish is an open-water fish with a short life cycle, so there are fewer fish diseases. However, the occurrence of taeniasis in neighboring provinces and cities is a wake-up call to the waters where the transplantation of large silverfish has been successful. Taenia solium is widely found in various reservoirs in Northeast China, but it has not been paid attention to because it used to live mainly in small miscellaneous fish. Infected with Taenia solium, the reproductive organs atrophied and could not reproduce naturally. However, the transplanted waters need to collect fish eggs for proliferation year after year to supplement the number of remaining populations. It consumes a lot of manpower, material resources and financial resources.

There is no very effective way to treat the fish disease in the reservoir. We have taken some positive preventive measures from the aspect of cutting off the life history of Taenia solium. The main thing is to control the final host of Taenia solium-birds. To reduce the chance of infection of the big silverfish.

5. Artificial multiplication and release to increase the number of supplementary populations

After spawning in natural waters, due to the influence of various factors in the water, the fertilization rate and hatching rate are very low. In order to ensure the number of supplementary populations in the waters, in addition to ensuring a reasonable retention, timely capture sexually mature parent fish for artificial reproduction, and return fertilized eggs to the original waters, so as to supplement and prevent the shortage of natural fecundity and increase the number of supplementary populations is a means of artificial proliferation of large silverfish resources. Since the winter of 1997 after the successful transplantation of large silverfish, we have carried out the artificial proliferation of large silverfish in Hangali Reservoir year after year. The practice shows that this measure is very effective.

VI. Strengthen the management of fishery administration and do a good job in resource protection

Resource protection is an important measure to transplant large silverfish, multiply fishery resources and ensure the sustainable utilization of fishery resources. It is necessary to formulate feasible measures for the protection of transplantation and proliferation of large silverfish. Determine the breeding reserves, no-fishing areas and no-fishing periods of the big silverfish, strictly implement the Fisheries Law of the people's Republic of China, and put an end to all bad acts that destroy the resources of the big silverfish.

The large silverfish is an improved species of aquatic products, and the artificial transplantation technology should be mastered by the state or scientific research departments to ensure its purity and popularize it scientifically and reasonably. It is not suitable for individuals to do the promotion of this improved variety. The state should also include it in the management of seed laws and regulations in order to more effectively ensure the promotion of large silverfish at home and even internationally.