Technical communication

How does recirculating aquaculture improve the quality of aquaculture seedlings

Over the past 40 years of reform and development, China's aquaculture has developed rapidly, with the output of aquaculture accounting for more than 60% of the world's annual output, realizing the magnificent transformation from "it is difficult to eat fish" to "there are fish every year". The consumption of aquatic protein accounts for more than 30% of the consumption of animal protein in China, and the per capita proportion has reached twice the world's per capita level. The great achievements of Chinese aquaculture are mainly attributed to policy, resources and technical factors, among which artificial breeding of seedlings, creation of new varieties and healthy breeding have played an important role. Up to now, more than 240 new varieties of aquatic products have been approved by the national Aquatic original seed and improved seed examination and approval committee, and the industrial chain of "breeding - breeding - promotion" of aquatic seed industry has gradually formed. The seedling breeding showed a diversified pattern, such as national, provincial, enterprise, small family and so on. The industry pays more and more attention to the "brand seedling" market. According to the important deployment of "Promoting green and healthy aquaculture" made in the No.1 document of the Central Government in 2020 and the relevant work requirements of several Opinions on Accelerating the Green Development of Aquaculture industry, the Ministry of Agriculture and Rural Affairs will implement the "five actions" of green and healthy aquaculture from 2020. Among them, "aquaculture drug reduction action" and "aquatic seed industry quality improvement" have repeatedly emphasized the quality of aquatic seedlings.

Good aquatic seedling has high efficiency, high quality, disease resistance and resistance. However, in the aquaculture industry, there is often a "good seedlings are not good for three to five years" phenomenon, especially the occurrence of diseases seriously harm the promotion and application of seedlings and the healthy development of the industry. For example, in recent years, the outbreak of crucian carp herpesvirus disease caused the death of a large number of commercial fish in summer, and the breeding industry of crucian carp gibelio shrank sharply. According to China's aquatic animal health report, the economic loss caused by diseases in the fishery industry amounts to about 40 billion yuan every year. Throughout the domestic aquaculture important disease and epidemiological regularity, carrying pathogenic aquatic fingerlings shall be examined problem has become one of the important factors of high incidence of breeding of aquatic animal diseases, such as South America white shrimp prawn WSSV and deeply cell worm, salmon cells swelling virus (ISKNV), allogynogenetic crucian carp, carp herpes virus and honghu iodine bubble, big sea bass of iris and slug viruses, And so on.

The Ministry of Agriculture and Rural Affairs formulated and promulgated the "Aquatic seedling management measures" requirements, to strengthen the origin of aquatic seedling quarantine; However, seedling breeding without specific disease has not received sufficient attention from seedling farms, enterprises and farmers. Especially for some varieties with low technical threshold for seedling propagation, there are some small family seed farms and "earth cannon seedlings". In some seedling farms, the preservation and breeding of fine varieties are not standardized, the investment is insufficient, and the disease prevention and control are not paid enough attention. There are some cases where the parents and the seedlings are directly purchased from the market to breed large-size commercial fish, resulting in a very high risk of pathogens carried by the parents and the seedlings. Fortunately, some of the main players in the seedling industry have fully recognized the importance of seedling pathogen detection in green and healthy aquaculture. For example, in Rudong, Jiangsu province, the local Vannaeus vannaeus Association has established a seedling detection platform to provide testing services for seedling farms and farmers. Before and after taking the seedlings, the farmers should decide whether to buy the seedlings or continue the cultivation according to the test results of WSSV and shrimp liver and intestinal worms issued by relevant testing institutions. In this way, due to the farmers' full recognition of the risk of pathogens carried by the seedlings, the shrimp seedling farms or enterprises must pay attention to the breeding of seedlings without specific diseases and improve the quality of the seedlings.

Diseases in aquaculture animals are often caused by a combination of several factors. Specific pestilent-free (SPF) seedling is not the ultimate solution for all diseases in farming, but it is one of the key measures to control important infectious diseases. The construction of pestilon-free seedling farms is an important practice towards the regional management of animal diseases, which has been recognized by more and more countries and regions. Aquaculture drug reduction action plan requires "strengthen the quarantine of the origin of seedling, create no specified disease aquatic seedling field", is an important measure to control major disease from the source of seedling, promote the green development of aquaculture industry and ensure the quality and safety of aquatic products.

The breeding of pestilence-free seedling and the construction of seedling farm must depend on a complete set of relevant technical systems and management measures for the construction of pestilence-free aquatic seedling farm. At present, China has carried out the construction of aquatic animal disease seedling farms in koi, rainbow trout, South American shrimp and other species of pilot. For other important breeding varieties and diseases, there is still a lack of systematic experience and technology, and it is urgent to carry out research and demonstration of specific disease-free seedling breeding technology system: (1) Monitor and evaluate the risks of various production elements (water, species, bait, tools, personnel, etc.) in the process of introducing, spreading and retaining different pathogens, and formulate epidemic prevention technical specifications for effectively cutting off the key nodes of pathogen transmission in aquaculture; (2) Explore and establish the breeding environment of important breeding varieties, the purification technology of parental pathogens, and the biological security technology system of seedling field; (3) Develop technical standards for sampling and detection of latent infection (recessive infection) at seedling stage; (4) Strengthen the quarantine publicity of aquatic seedling production areas and strengthen the ability training of quarantine personnel.