Analysis of the problems existing in the development of the eel industry and the countermeasures and suggestions

I. Seedlings and fingerlings

The main species farmed for eel in China are the Japanese eel (Anguilla japonica) and the European eel (Anguilla anguilla). The resources of both the European eel... have already approached exhaustion, with annual production falling from 3,000 tons 30 years ago to 100-200 tons. From June 3 to 15, 2007, at the Conference of the Parties to the "Washington Convention" (CITES) held in the Netherlands, the European eel was listed in Appendix II of the Convention on Endangered Species of Wild Fauna and Flora, and this will be formally implemented starting in January 2009: China imports about 60 tons, or about 150 million individuals, of European eel seedlings and fingerlings annually, farmed European eel accounts for more than 1/3 of eel production, and European eel accounts for about 40% of exported roasted eel. Japanese eel resources have also severely declined. In recent years, the seedling and fingerling resources of Japanese eel in Asia have remained at about 100 tons, and the annual catch in recent years has remained at 80-100 tons. In 2008, the output of European eel seedlings and fingerlings was about 90 tons, half of a normal year. The output of Japanese eel seedlings and fingerlings was about 35 tons, one third of a normal year. The severe shortage of seedling and fingerling resources has led to soaring prices. Moreover, artificial breeding of eel seedlings and fingerlings will not be able to form production capacity in the near future.

China is the world's largest eel producing country. There are 1,700-1,800 eel farms nationwide, with a farming area of about 100,000 mu and an annual output of about 130,000 tons. The quantity of Japanese eel seedlings and fingerlings required for China's farming scale should be about 50 tons, and that of European eel seedlings and fingerlings 60 tons, with total annual demand for seedlings and fingerlings at more than about 100 tons. In 2008, it is estimated that China can stock 5.5 tons of Japanese eel seedlings and fingerlings and 40 tons of European eel seedlings and fingerlings. Therefore, seedling and fingerling resources will severely restrict the normal development of China's eel industry.

Suggestions

1. Carry out research on and promotion of farming techniques for other eel species

There are 19 species of eel worldwide, and currently only 2-3 species are available for artificial farming. In addition to the dominant species, the Japanese eel and the European eel, China has also farmed small amounts of the American eel (Anguilla rostrata) and the marbled eel (Anguilla marmorata). In addition, among the 12 tropical eel species of the Pacific and Indian Oceans, several have relatively large resources, and efforts should be concentrated on research into artificial farming techniques and species identification techniques. On the basis of successful experience in introduction, trial farming and research, the farming of new species should be promoted.

2. Continuously carry out research on artificial breeding techniques for the Japanese eel

Japan and China have carried out research on artificial breeding techniques for the Japanese eel for many years. In recent years, Japan has made breakthrough progress and bred glass eels, while China still remains at the leptocephalus level of the 1990s. Continuously conducting artificial breeding research will provide the most basic material foundation for China's eel artificial breeding to maintain an advanced level, ultimately solve the dependence of seedlings and fingerlings on natural resources, and safeguard the healthy development of the eel industry.

II. Diseases

Research on eel diseases in China has advanced in step with the development of farming. To date, the main diseases occurring during the farming of Japanese eel, European eel and American eel and their causative pathogens or causes have been almost completely understood, and effective prevention and control techniques have been developed. Beginning in 2001, disease monitoring and forecasting have been carried out for farmed eel, with a forecast accuracy rate of more than 90%. China's eel disease research has focused on research into pathogenic organisms and control drugs. Although this has played a positive role in increasing survival rates and reducing disease losses in farming production, it has at the same time created a situation of serious dependence on disease control drugs in farming production and sometimes drug abuse, affecting product quality and safety. Beginning in 2002, China's disease research began to focus on the development of pollution-free disease control techniques. In immunological research, inactivated vaccines and subunit vaccines for Vibrio vulnificus and anti-idiotypic antibody vaccines for Aeromonas sobria have now entered pilot testing in farming production, a vaccine with an approved approval number is available for Aeromonas hydrophila, and anti-idiotypic antibody vaccines for Edwardsiella and Vibrio anguillarum have obtained pilot testing approval documents; effective progress has been made in immunological research on Ichthyophthirius multifiliis. In biological control technology, probiotics have been widely used in eel farming, such as photosynthetic bacteria and Bacillus for controlling farming water quality, Bdellovibrio for treatment of farming water bodies and water@#@254@#, and Lactobacillus, Bacillus and Streptococcus faecalis as feed additives; indigenous probiotics isolated from the intestines of farmed eel have achieved good results in controlling intestinal flora imbalance and increasing feeding amount and feed conversion rate.

At present, the diseases seriously threatening the eel industry mainly include parasitic monogenean trematodiasis and the protozoan disease ichthyophthiriasis, as well as fungal diseases. Because no effective and safe drugs have been developed, serious losses in farming production have resulted, and moreover, because there are no good alternative techniques for drug control and no substitute drugs for banned drugs, hidden dangers to product quality and safety have arisen.

Suggestions

1. Strengthen research on and development of alternative drugs

Because parasitic diseases inevitably occur regardless of which farming model is adopted, and fungal diseases are also very prone to outbreaks in low-temperature seasons, screening safe and efficient control drugs is a necessary path to solving practical problems. However, China has relatively few scientific researchers and funds allocated in this direction, and relevant units should be organized in the near future to carry out tackling of key problems.

2. Strengthen research on and development of immunity and biotechnology in the prevention and control of eel diseases

The application of immunity and biotechnology in disease prevention and control generally has good application prospects because of advantages such as not producing drug residue hazards or drug resistance. Therefore, strengthening research on and development of immunity and biotechnology, including diagnostic techniques, in eel disease control will be of great significance for developing eel disease control in a harmless direction, ensuring product quality and safety, and safeguarding the healthy development of the industry.

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