Problems and countermeasures in the development of eel industry

I. Seedling

The main species of eel cultured in China are Japanese eel and European eel. The two resources of European eel have been nearly exhausted, and the annual output has dropped from 3000 tons 30 years ago to 100 million 200 tons. At the meeting of States parties to the Washington Convention (CITES) held in the Netherlands on June 3-15, 2007, European eel was listed in the Appendix Ⅱ to the Convention on Endangered Animals and plants, and will be formally implemented from January 2009: China imports about 60 tons of European eel seedlings, about 150 million eggs. Farmed European eels account for more than 1% of the eel production, and European eels account for about 40% of the exported roasted eels. The resources of Japanese eel are also in serious decline. In recent years, the stock of Japanese eel seedlings in Asia has been maintained at about 100 tons, and the annual catch has been maintained at 80 tons per year. The seedling yield of Anguilla Anguilla in 2008 was about 90 tons, which was 1 month 2 of the normal year. The seedling yield of Japanese eel is about 35 tons, which is 1 × 3 of the normal year. There is a serious shortage of seedling resources, resulting in a sharp rise in seedling prices. However, it is impossible to form the production capacity of artificially propagated eel seedlings in recent years.

China is the largest eel producing country in the world. There are 1700-1800 eel breeding farms in China, with a culture area of about 100000 mu and an annual output of about 130000 tons. The amount of Japanese eel seedlings needed for culture scale in China should be about 50 tons, and European eel seedlings should be 60 tons. In 2008, it is estimated that China will be able to put 5.5 tons of Japanese eel seedlings and 40 tons of European eel seedlings. Therefore, seedling resources will seriously restrict the normal development of China's eel industry.

Suggestion

1. Research and Popularization of Culture techniques for other species of Eel

There are 19 species of eel in the world, at present, there are only 2 and 3 species of eel for artificial culture. in addition to the dominant species of Japanese eel and European eel, American eel and flower eel are also cultured in China, and among the 12 species of tropical eel in the Pacific and Indian Ocean, there are several species with large resources, so efforts should be focused on artificial culture and breed identification. On the basis of the successful experience of introducing trial culture and research, popularize the culture of new varieties.

two。 Study on artificial propagation of Japanese eel (Anguilla japonica)

The artificial breeding technology of Japanese eel has been carried out in Japan and China for many years. In recent years, Japan has made a breakthrough in breeding glass eel, while China is still stagnant at the level of willow leaf eel in the 1990s. The continuous research on artificial reproduction of Anguilla Anguilla will provide the most basic material basis for maintaining the advanced level of artificial reproduction of Anguilla Anguilla, finally solving the dependence of seedlings on natural resources, and maintaining the healthy development of the eel industry.

II. Diseases

The disease research of Anguilla Anguilla has been carried out synchronously with the development of eel culture in China. up to now, the main diseases and pathogens of Japanese eel, European eel and American eel have been fully understood, and effective control techniques have been developed. Since 2001, disease prediction and prediction of farmed eel has been carried out, and the prediction accuracy is more than 90%. The research on the disease of eel in China focuses on the study of pathogenic organisms and control drugs. Although it has played a positive role in improving the survival rate and reducing disease losses in aquaculture production, it has also caused serious dependence on disease control drugs and sometimes drug abuse in aquaculture production, which affects the quality and safety of products. Since 2002, disease research in China began to pay attention to the development of pollution-free disease control technology. In the aspect of immunological research, the inactivated vaccine and subunit vaccine of Vibrio vulnificus and the anti-idiotypic antibody vaccine of Aeromonas aeruginosa have been carried out in pilot-scale production, and the vaccine of Aeromonas hydrophila has been approved. Edwardsiella and Vibrio eel anti-idiotypic antibody vaccines have been approved in the pilot test, and effective progress has been made in the immunological research of melon insects. In terms of biological control technology, probiotics have been widely used in eel culture, such as photosynthetic bacteria and Bacillus to control water quality, Bdellovibrio in culture water and water treatment, Lactobacillus, Bacillus and Streptococcus faecalis as feed additives. The probiotics isolated from the intestinal tract of cultured eel have achieved good results in controlling the imbalance of intestinal flora, increasing feed intake and feed conversion rate.

At present, the diseases that seriously threaten the eel industry are parasitic paragonimiasis, protozoan cucumber disease and fungal diseases. due to the lack of effective and safe drugs, there are serious losses in culture and production. what's more, there are no good drug control alternative technologies and banned drug substitution drugs, which lead to hidden dangers in product quality and safety.

Suggestion

1. Strengthen the research and development of alternative drugs

Parasitic diseases will inevitably occur no matter what culture mode is adopted, and fungal diseases can easily break out in low temperature seasons. in this area, screening safe and efficient control drugs is a necessary way to solve practical problems. However, our country has set up a project and invested less scientific research personnel and funds in this direction, so we should organize relevant units to tackle key problems in the near future.

two。 Research and development of strengthening immunization and biotechnology in the prevention and control of eel diseases

The application of immunization and biotechnology in disease prevention and control has a good application prospect because it generally does not produce drug residue harm and drug resistance. Therefore, strengthening the research and development of immunization and biotechnology in eel disease control, including diagnostic technology, will be of great significance for the harmless development of eel disease control, ensuring product quality and safety, and maintaining the healthy development of the industry.

III. Feed

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