Jiang Yulin
Shenzhen Animal and Quarantine Bureau
40 Heping Road, Shenzhen 518010
People's Republic of China
Jiang Yulin. 1996. A review of traditional and innovative aquaculture health management in the People's Republic of China. In Health Management in Asian Aquaculture. Proceedings of the Regional Expert Consultation on Aquaculture Health Management in Asia and the Pacific. R.P. Subasinghe, J.R. Arthur & M. Shariff (eds.),p 88–103. FAO Fisheries Technical Paper No. 360, Rome, FAO 142 p.
Abstract
In 1994, China contributed 60.4% to the total world aquaculture production. Although freshwater and marine fish production increased rapidly over the past decade, marine shrimp culture suffered serious losses due to disease outbreaks. It has been said that these outbreaks of virus disease are partly management oriented. In order to find an effective solution to prevent disease outbreaks, the concept of “putting prevention first” has now been introduced, and this paper describes the current health management strategies that are being practiced in Chinese aquaculture.
AQUACULTURE IN THE PEOPLE'S REPUBLIC OF CHINA
Prior to 1980, fish production in China was dominated by marine capture fisheries and aquaculture accounted for less than one million metric tonnes (mt). This limited production, which was inadequate to meet demands, came mainly from the extensive freshwater pond culture of four species of Chinese carps; grass carp (Ctenopharyngodon idella), black carp (Mylopharyngodon piceus), silver carp (Hypophthalmichthys molithrix), and bighead carp (Aristichthys nobilis). The culture of finfish in lakes and reservoirs and of marine shellfish was also practiced, but their contributions were not significant. Since then, aquaculture has developed rapidly, with production increasing to some 8 million mt at present. Indeed, aquaculture has achieved such importance that by 1992 it contributed more than half of the total aquatic production.
Freshwater Aquaculture
Intensive high-production fish ponds for the culture of market fish have been set up in the suburbs of large cities, with a total area of 167 000 ha under culture in 1991 (11 000 ha in the suburbs of Shanghai alone), and yields reaching 11.4 mt/ha. Pond culture of fish has always been the mainstay of Chinese aquaculture and an important channel for increasing the output. For example, in 1988 some 1.4 million ha of ponds produced 2.9 million mt of fish i.e. 35% of the culture area contributing 75% of the fish produced via freshwater culture. During the 10 years from 1978-1988, production increased five fold, while the area of ponds doubled.
There are lakes and reservoirs covering an area of 12 million ha, but about only one fifth of them are used for aquaculture. Low density culture is carried out in large lakes and intensive culture in cages and enclosures. Efficiency is generally low, the average output being 60 kg/ha for lakes and 210 kg/ha for reservoirs. Cage-culture production is on the order of 600 mt/ha.
Industrial fish farming, which includes the use of warm flowing water from power stations, rainbow trout (Oncorhynchus mykiss) culture using cold flowing water, and industrial fish culture using confined circulating water, has developed very quickly. In Shanghai, yields have reached 270 mt/ha for rainbow trout and 750-1300 mt/ha for tilapia. Many freshwater species are cultured in China, such as rainbow trout, cels, tilapias, shrimps, pearl shell, frogs, freshwater crabs, turtles etc.
In Hubei Province, for example, freshwater aquaculture production was 0.82 million mt in 1992, half being derived from non-traditional species.
Marine Culture
Shrimp farming began in China in 1978 and special attention was paid to the culture of Penaeus chinensis, P. japonicus, P. monodon and P. penicillatus. The main form of culture utilized interconnected ponds occupying large areas. Shrimp farming developed so quickly that from 1978 to 1992, the area under culture increased 110 fold, eventually reaching 140 000 ha, and the output increased 460 fold, from 2 549 mt in 1980 to 200 000 mt in 1988, an annual rate of increase of more than 75%. The production value was 4 billion Chinese Yuan (US$ 800 million). Seventy percent of all the prawn farming operations were located in the Bay of Bohai Sea and two peninsulas. However, in 1993, a serious epidemic broke out; production decreased rapidly to 80 000 mt, and still continues to decline.
Because of their high economic potential, some marine fish (grouper, seabream, snapper, seabass etc.) also attracted the attention of fish farmers. These fish are cultured in cages or in indoor tanks. Because of the short history of this type of culture, output was not very high (less than 30 000 mt in 1987).
Shellfish culture in shallow areas has also developed very quickly. In 1950, the area under culture was 13 000 ha, with an output of less than 10 000 mt. By 1990, the area used for this type of culture had expanded to 350 000 ha, with more than 65% of available area being under production. The output of shellfish reached 700 000 mt in 1987, with about 65% of total production from marine culture.
The Aquaculture Situation in 1992
In 1992, total aquatic production was on the order of 15 million mt, of which 7.76 million mt was derived from aquaculture (52% of the total), 5.34 million mt from freshwater culture and 2.42 million mt from marine culture. The freshwater area under culture was 3.8 million ha (1.5 million ha of ponds, 2.3 million ha of lakes and reservoirs) of which 20 000 ha was for enclosed nets, 200 000 ha for industrial fish farming and 293 000 ha for special species culture. The area used for marine culture was 400 000 ha, with 140 000 ha being used for shrimp farming.
PRESENT STATUS OF AQUACULTURE HEALTH AND MAJOR PROBLEMS1
The status of aquaculture health in China was good before the 1980s. At that time, the pond culture of freshwater carps under low stocking densities was the major form of aquaculture practiced, and most of the common diseases seen in small ponds were basically under control, a result of research on fish pathology and the use of traditional health management strategies and control measures which were well established.
However, during the past 10 years losses due to pathogens have increased in both in extent and severity, along with the use of increased stocking densities, expansion of culture area, and the introduction of many new species and culture systems. To date, about 200 different diseases have been discovered; about 20 of these are serious diseases which can produce epizootics, sometimes with disastrous consequences for Chinese aquaculture. They have become the major factor hindering the development of aquaculture. For example:
Bacterial hemorrhagic septicemia of fish cultured in fresh water
This is an acute disease causing high mortality which is prevalent over more than half of China's mainland. It has threatened silver carp, bighead carp, golden carp, Chinese bream and common carp since the late 1980s. A loss of more than 100 million Chinese Yuan (US$ 20 million) was suffered annually for three consecutive than 60 million Chinese Yuan (US$ 12 million). The pathogens isolated were opportunistic bacteria common in many areas of the world: Aeromonas punctata, Vibrio fluvialis and Yersinia ruckeri; however, their virulence increased more than 10 or even 100 times in adverse circumstances.
1 Recent publication on diseases affecting Chines aquaculture are given in Appendix I.
Diseases of penaeid shrimp in ponds
Serious epidemic diseases appeared in south China in 1990 and spread to the whole of China in 1993, endangering Penaeus chinensis, P. japonicus, P. monodon and other species. More than 76% of shrimp ponds suffered reduced production, with a loss of some 120 000 mt of shrimp valued at up to US $ 400 million.
Hemorrhagic disease of grass carp
Hemorrhagic disease is the most serious viral disease of grass carp during the fingerling stage, with only 30% of the fish surviving to reach the market. An old saying “become a millionaire if there is no epidemic in cultured fish” points to this disease. To reduce the serious loss of fingerlings, an inactivated vaccine was prepared and mortality was lowered from 70% to 30% after injection. Several billion grass carp fingerlings are vaccinated every year, a method that is very time consuming. Some fish farmers do not pay attention to immunoprophylaxis, but hope to have a good medicine to cure the viral disease. Others ignore environmental hygiene and cause man-made epidemics. As a result, hemorrhagic disease still occurs in many regions and causes serious losses.
The current aquaculture health situation
The number of common pond diseases is rising again, and new diseases of fish cultured in ponds (new pathogens, or pathogens spreading to new geographic areas or infecting new hosts) occur constantly.
There are about 40 common diseases which occur in fish ponds, of which ten, such as hemorrhagic disease, bacterial enteritis, bacterial gillrot, trichodiniasis, ichthyophthiriasis, sinergasiliasis etc. still prevail. As methods of prevention and cure were found, they were kept under control in the 1960s and 1970s. However, at present, many fish farmers do not take preventive measures by using medicine or vaccines, and mortalities have risen. For example, in Honghu Lake, the survival rate of grass carp fingerlings is only 30%. The prevalence of Sinergasilus reached 50% and morbidity due to enteritis and gillrot was above 50%. The situation in other regions was similar. This trend towards increased disease will continue if aquaculture health management is not emphasized. The appearance of epidemic diseases in large lakes and reservoirs makes their control very difficult.
Fish cultured in cages and enclosures are easily infected by pathogens causing epidemic diseases such as pox disease, myxosporidasis, dactylogyriasis, sinergasiliasis etc. These diseases are becoming much more common, and are causing serious losses. For example, an epizootic caused by Ergasilus broke out in a reservoir near Tianjing City, and several hundred common carp died in three or four days, producing a terrible smell which could be detected at 5 km distance. However, control of diseases in lakes and reservoirs is very difficult, as the areas involved are so large. Furthermore, there are no practical methods to control some of the diseases (e.g. myxosporidasis). Sometimes waste water from factories is discharged into water bodies and causes mass mortalities.
• Many diseases appear in newly cultured species.
Newly cultured species are frequently affected by pathogens. The scale of the culture of these animals has developed rapidly, and most are kept at high stocking density and fed artificial feeds. There is no previous experience nor existing culture formats for these new species to assist farmers in keeping them healthy. This makes disease occurrence likely. We cannot even determine the cause of some diseases and do not know how to control them, thus aggravating the situation and hindering the development of aquaculture. Some important diseases are described below.
In the 1980s, infectious diseases seriously affected pearl culture. The culture of Hyriopsis cumignii, a species which produces high quality pearls, almost disappeared became of its low resistance to disease. Farmers had to culture another species (Cristaria plicata) in its place, even though the quality and quantity of pearls it produced was not as good.
Soft-shelled turtle is normally very resistant to disease, but even they suffer high mortality under the artificial conditions of culture.
More than 60% of pond-cultured Chinese perch in Zhujiang Delta became ill and no effective control measures could be devised because these fish eat only live fish.
The death of freshwater crabs in only one village in Hubei Province resulted in losses of about 6 million Chinese Yuan (US$ 120 000).
• Many epidemics occur in industrial fish farming.
Economic losses are usually serious and control difficult whenever diseases occur in industrial fish farming because fish are cultured in a high density environment. Furthermore, the poor quality of artificial feeds often leads to illnesses from nutritional or unknown causes. An example is obesity and exophthalmus of tilapia, which led to mortalities where no pathogen was found.
In summary, the situation with regard to aquaculture health has steadily deteriorated over the last 10 years, resulting in a variety of diseases which have endangered new areas and caused increased losses. These diseases are major limiting factors to aquaculture development, and it has been estimated that production would be 10–25% higher if they were controlled. The occurrence of disease is closely related to both the state of the local environment and culture patterns being used.
Major causes of health problems
Deteriorating aquaculture environment and poor ecological conditions, leading to poor water quality (low pH and high NH3 and NO2 concentrations) and rapidly rising total amount of bacteria in water. Results are that on the one hand there is an increased susceptibility of cultured fish to disease, and on the other, the growth of pathogens is favored.
The causes are:
Many new fish farmers lack experience in health management.
Sludge from fish ponds in many regions is not cleared away in time for improvement of cultivation. In order to save money and manpower, some farmers even ignore basic preventive measures, such as pond disinfection.
To achieve high profits, farmers culture fish at irrationally high densities. This overstocking leads to difficulties in maintaining good water quality.
Over-exploitation of lakes and reservoirs, exceeding the ecological capacity.
Industrial water pollution; some ponds near the suburbs are contaminated with chemicals.
• Lack of a good system of prevention, monitoring and quarantine.
As aquaculture developed, cultured species were frequently transferred from one region to another, carrying their pathogens with them. A serious shrimp disease which occurred in 1993 was obviously caused by the transfer of large numbers of Penaeus japonicus infected with viruses from southern to northern China. In many regions of northern China, these P. japonicus became diseased and died, with the disease spreading to P. chinensis. Those shrimp farms that were not in a position to exchange water from outside or which were unable to get fresh feeds from the epidemic area were only slightly influenced.
Another example is that in 1986, eyed eggs of rainbow trout were imported from Japan without strict quarantine. This importation lead to an outbreak of acute infectious disease (IPNV) in Shanxi Province causing 90–95% mortality.
• Irrational programs of development and culture patterns.
In some areas, several thousand ha of shrimp ponds or fish ponds are linked together. Some of them usually have no preventive installations for the treatment and disinfection of source and discharge water, so disease spreads widely once it appears in one or two ponds.
Protection of the environment was ignored when rapid large-scale development was planned. Waste water is drained from the ponds without treatment, causing pollution, which in turn, adversely affects culture conditions.
• Research conducted is inadequate to meet the demands of aquaculture development.
To some extent, inadequate basic research affects the subsequent application to aquaculture practice. Important areas where more research is needed include the study of the mechanisms of pathogenesis, the origin of pathogens, the distribution and epidemic patterns of diseases (especially viral diseases), the role of environmental stress in determining host resistance and pathogenicity, the prediction and monitoring of epidemics etc. Long-term research is needed. The use of some drugs is already limited or prohibited (e.g., HgNO3) and some effective methods for disease control in small ponds, such as hanging baskets or bags with drugs in pond water to prevent infection, are not suitable for use in big lakes and flowing water. Therefore research to develop new drugs and new methods of treatment is needed. .cl.
HISTORY AND PRACTICE: EXAMPLES OF AQUACULTURE HEALTH MANAGEMENT
Although Chinese freshwater aquaculture has a history of several thousand years, the scientific study of fish disease was begun only in the past few decades. However, people have accumulated some experience on health management. For example, in the polyculture of the four commonly raised carps, it is known that water quality is associated with parasitic infections causing diseases. In the 1950s and 60s, research on fish diseases expanded very quickly and a set of traditional health management systems was formed.
Recommendations include: the use of quick lime to disinfect ponds, the use of mixed compost (manure) to feed fingerlings and the hanging of baskets filled with bleaching powder or of bags filled with CuSO4 at the feeding sites. All these methods are very easy to operate and are effective against fish diseases. Hanging drug bags or baskets are an ideal and practical method, as fish come into contact with the drug for disinfection. Over-dose is avoided, as the fish can keep away voluntarily if the concentration of drugs at the site is too high.
For prevention and cure of diseases, fish farmers follow the principle “prevention prior to illness and early treatment immediately after.” They also carry out other efficient steps, the “three disinfections” and the “four rules.” The implementation of these has proved indispensable to fish culture. For example:
On regular use of drugs for prevention of diseases: Use drugs prior to the epidemic season of some fish diseases to reduce morbidity. For example, hanging bags filled with CuSO4 and FeSO4 against protozoans and filled with bleaching powder to prevent bacterial diseases.
Clean the pond environment, including rapid discarding and burying of any dead fish in time to limit the spread of disease.
Disinfect the tools and use them separately for individual ponds.
Three disinfection methods:
To clear and disinfect the ponds (either dry ponds or ponds with water) thoroughly using quick lime or bleaching powder.
To disinfect juveniles and fingerlings, use 3–4% salt, 10 ppm bleaching powder, 8 ppm CuSO4 or 20 ppm KMnO4 for 20 min.
To disinfect feeds and feeding sites (feeds should be clean, and kept fresh and alive), immerse plant feeds in 0.05% bleaching powder for 20–30 min; disinfect 300 kg manure fertilizer with 120 g of bleaching powder or apply into the water after complete fermentation; disinfect the feeding sites by hanging baskets filled with bleaching powder and by casting the disinfectant around them.
Four rules in feeding:
Choose the quality (either dry or fresh) and the amount of feeds; fix the feeding site and time.
Efficient control methods have been found for many fish diseases that often caused serious losses in the past. Diseases such as gillrot, enteritis, hemorrhagic disease, ichthyophthiriasis, fungus disease etc. in ponds are now under control. The history of research development in fish diseases is almost the same in China as in other countries. At first, research was carried out on parasites, then the focus turned to bacterial and viral diseases.
In brief, prevention is the major element in traditional aquaculture health management. It ensures the minimum possibility for fish to come into contact with pathogens and become infected.
STATUS OF INNOVATIVE AQUACULTURE HEALTH MANAGEMENT IN CHINA AND COMPARISON OF ITS EFFECTIVENESS WITH TRADITIONAL MANAGEMENT
Generally speaking, the policy of “putting prevention first” is still maintained in present health management. It conforms with the changing aquaculture situation, including the extended scale of culture, the increased production and the rise in stocking densities, and also, the occurrence of many new viral and bacterial diseases. Of course, the advantages and disadvantages of these measures and policies still need further evaluation through practice.
Improving the pattern of culture in ponds
The intensification of aquaculture practices which began in the late 1970s has had a great impact on the environment, causing disease epidemics and affecting the disease resistance of fish. New culture methods stressing high production from the ponds were adopted, modifying the existing traditional culture patterns.
In the past, fish farmers never fed pond-reared fish during the winter and kept the fish under high density. Studies indicated that fish still require adequate nutrition and energy in winter. In the new culture method, fish are kept in the original ponds at low density, reducing injuries to the body surface, and feeds are replenished on sunny days, resulting in healthier fish and enhancing their resistance to diseases during winter.
In the traditional polyculture method, the ratio of grass carp to silver carp (and/or bighead carp) was 1:3. However, this ratio was considered out of proportion, as the efficiency of energy transformation was not high enough. To meet the demands of silver and bighead carp, pond water had to be fertilized, often resulting in bad water quality and inducing disease in grass carp. Now the ratio has been changed from 1:3 to 1.5–2.5:1, a measure which can efficiently raise survival rates, increase production and improve water quality. Using these new methods, production rose from 690 kg/ha in 1978 to 2070 kg/ha in 1988.
Immunization against viral and bacterial diseases
In the past, the prevention of fish disease was mainly directed towards eliminating infectious sources and severing the routes of transmission. Now, more attention is paid to enhancing the general level of health and increasing disease resistance. With parasitic diseases almost under control, viral and bacterial infections are becoming increasing prominent. There are no drugs to cure viral infections. Immunological methods of prevention, such as the use of inactivated vaccine against hemorrhagic disease, and bacterial vaccines against gill-rot, enteritis, hemorrhagic septicemia, vibriosis etc., have been developed.
The use of vaccines in aquaculture has been approved and accepted by fish farmers and the results are fruitful. The methods used in the preparation of vaccines have also advanced, beginning with inactivated vaccines, and then to live vaccines, sub-unit vaccines and gene vaccines, the aim being to increase the specificity, effectiveness and safety. However, it was found that after fish were immunized with inactivated vaccine against hemorrhagic disease, the morbidity of some bacterial diseases, such as enteritis and gillrot, was also clearly reduced. It is suggested that the impurity of the vaccine plays a beneficial role by enhancing the nonspecific immune response of fish. Perhaps vaccines prepared from the organs of sick fish were actually a mixture against viruses and bacteria. Inactivated vaccines prepared from organs of sick fish have been well accepted by fish farmers. Effectiveness, convenience and low cost are the most significant requirements.
Another trend is the use of additive drugs such as peptidoglycan (PG) to fortify the immunity of fish.
Use of new drugs in aquaculture
Many new drugs have been produced for disease control in aquaculture. These include various disinfectants e.g., PVP-iodine, CDB Cleraron (sodium dichloroisocyanurate) etc.; and various new types of antibiotics for oral use.
New drugs are undoubtedly more effective in killing pathogens than are those previously available. However, they themselves possess certain advantages and shortcomings and, in practice, their use must be individually evaluated. For example, CDB Cleraron is highly effective, convenient to transport and can clean ponds rapidly, fish being able to be stocked into disinfected ponds only a few days after treatment. If lime is used, 10 days are required. However, the former lowers the pH of water and cannot improve the quality of the water or the pond bottom sludge, so for long-term use, its effectiveness has yet to be fully evaluated.
The excessive use of antibiotics often leads to reduced resistance (e.g., fungal diseases may occur easily) and to formation of drug-resistant bacterial strains or the killing of beneficial bacteria.
Establishment and application of rapid detection methods
Because bacteria and viruses cannot be detected visually, new detection techniques developed through immunology and molecular biology are used, as these new methods are more reliable, sensitive and rapid. They may be the basis for enforcing quarantine rules. A number of research institutes are developing modern methods to detect pathogens of cultured species, such as IPN virus in rainbow trout and IHHNV in shrimp. However, these advanced methods are used only in research institutes and some quarantine departments and have not yet been widely adopted in all regions of China. Visual inspection is still widely used for on-site diagnoses, relying on the experience of the diagnostician.
Prevention of diseases by ecological methods
Researchers have paid attention to the relationship between the environment, fish health and disease. They realize that ecological control is the best way to combat potential pathogens and have begun to exploit new culture formats (e.g., relationships between density, benefit and health; the polyculture of shrimp and fish). A good example is the successful culture in water with low salinity of P. monodon carrying viral infections in their tissues.
Study of disease-resistant strains and specific pathogen-free fish
These studies are still underway, and it will be some time before their application is realized in China.
RESEARCH INSTITUTIONS INVOLVED IN PROMOTING AQUACULTURE HEALTH MANAGEMENT
The Bureau of Fishery, Ministry of Agriculture and subordinate Bureaus of Fishery in provinces and cities are in charge of fishery management, including disease control at the national level. They form an administrative system of management, and are responsible for planning fishery development and the scale of culture, circulating information of epidemic diseases in the various regions, organizing experts to formulate a policy for quarantine, arranging for institutes to tackle key problems etc.
Scientific research is being carried out by the following agencies and institutes:
Institutes of the Chinese Academy of Science (CAS): Institute of Hydrobiology, Institute of Oceanology, South China Sea Institute of Oceanology etc.
The Chinese Academy of Fishery Science (CAFS), which was founded in 1982, has a number of subordinate institutes: Yangtze Institute, Zhejiang Institute, Heilongjiang Institute, Center of Freshwater Fishery, Yellow Sea Institute, East China Sea Institute, South China Sea Institute, Zhujiang Institute etc.
Departments and research units of colleges and universities (there are groups or laboratories working on fish diseases, especially at many fishery colleges).
The Fish Disease Section of the Chinese Fishery Society (FDS/CFS) was set up in December 1985. Its main tasks are to carry out academic discussion and exchange, to organize symposia on special subjects, to offer technological training on the control of fish diseases, to edit and publish academic journals and popular science articles, and to initiate communication activities both at home and abroad. The Fish Disease Section holds national academic symposia every four years.
A network for fish disease control was founded in December 1990. It not only transmits and forecasts information concerning fish diseases, but also communicates information on new technologies, new drugs and new achievements in the field of disease control; offers various training courses; provides technology and consultation services; and coordinates the relationship between scientific research, production and concerned enterprises.
The major sources of current funds for fish health research:
Some key projects form part of a five-year plan for China, for example, studies on hemorrhagic disease in grass carp and epizootics in freshwater cultured fish. The subjects chosen must make important contributions to the development of the national economy, and have high applicability and feasibility.
The National Science Foundation of China (NSFC) and the Science Foundations of some provinces support basic research and new projects in science.
FUTURE PROSPECTS AND RECOMMENDATIONS
Aquaculture development should be based on disease prevention and on maintaining ecological balance
Health problems caused by the irrational distribution and over development of aquaculture cannot be solved by creating new medicines, but only by transforming aquaculture itself. The pattern and technology of culture should be improved so as to reduce stress on the environment and decrease risks to production (e.g., changing from a large area of single species production to multi-species production). In planning future development, we must readjust the amount and structure of culture, defining the culture scale according to levels sustainable by the environment in the area of the aquaculture development.
Research and development on diagnostic technology
We need two different types of detection techniques, which together, can form a preventive system covering multiple levels. One group of techniques is needed for on-site diagnosis to help fish farmers quickly determine the causative agents of problems, while the other groups are those techniques which should be applied in laboratories, and have high sensitivity and specificity for use in quarantine and the prediction of epidemic diseases.
Formulation of quarantine laws, improvement of detection to prevent pathogens from spreading artificially, and licensing of production
Our research should be directed towards the study of those diseases which have the highest economic impacts. Researchers should be strongly encouraged to study epidemic diseases occurring among new culture species, in cage culture, and in high density culture in big lakes and reservoirs and the marine environment.
Enhancement of fish farmers' knowledge
For example, the preventive measures taken against diseases in ponds in China are effective. The key problem is how to have them executed and popularized. Many fish farmers do not realize the relationship between the culture environment and disease. They accept that disease results only from the existence of pathogens and place their hopes in new medicines. Therefore, it is most important to raise their level of knowledge by offering training courses on fish health and preventive methods.
Enhancement of international cooperation
International cooperation should be increased in such areas as the exchange of standard antisera and antigens, the standardization of diagnostic procedures and the monitoring of diseases.
APPENDIX I
Some Recent Publications on Diseases in Chinese Aquaculture Systems
Chen Chileu and Pan Jinpei, 1992. Chapter 13, Prevention and control of fish diseases. In Cultivation of Chinese Freshwater Fishes (3rd edn.). Liu Jiankang and He Biwu (eds.) Science Press, Beijing, p. 519–629.
Chen Yanxin, Chen Hong, Han Xianpu and Li Wei, 1992. A viral epidemic disease of eel occurred in China. Chinese Sci. Bull. 23: 2910–2912.
Han Xiangpu and Li Wei, 1989. Study on edwardsielliasis of the eel. Acta Hydrobiol. Sinica, 13: 259–264.
Han Xianpu and Li Wei, 1993. Studies on the hemorrhagic open-mouth disease of Anguilla japonica. Acta Hydrobiol. Sinica, 17: 285–287.
Jiang Yulin and W. Ahne, 1989. Some properties of the etiological agent of the hemorrhagic disease of grass carp and black carp. In Viruses of Lower Vertebrates. W. Ahne and E. Kurstak (eds.) Springer-Verlag Publ., Berlin.
Jiang Yulin, Li Yan and Li Zhengqiu, 1991. Electron microscopic observation of pathogen of carp-pox disease. Acta Hydrobiol. Sinica, 15: 193–195.
Jiang Yulin, Li Zhengqiu, Han Guangshu, Wang Xue and Gong Xianghong, 1995. Electron microscopic observation of bacilliform virus in shrimp (Penaeus orientalis). Trans. Res. Fish Dis. No. 2. China Ocean Press, Beijing.
Jiang Yulin, Yu Ping and Li Zhengqiu, 1990. Rapid detection of infectious pancreatic necrosis virus (IPNV) with the enzyme-linked immunosorbent assay (ELISA). Acta Hydrobiol. Sinica, 14: 276–279.
Meng Qingxian, 1991. Handbook of the Prophylactics and Therapeutics of Shrimp Diseases. Ocean University of Qingdao Publication, Qingdao.
Pan Jinpei (ed.), 1988. Handbook of the Diagnosis, Prophylaxis and Therapeutics of Fish Diseases. Shanghai Scientific and Technical Publishers, Shanghai.
Xu Bohai, Yin Zhan, Wu Yushen and Cai Taozhen, 1991. Studies on an outbreak of a new epizootic in silver carp and bighead carp - Yersinia ruckeri, a new pathogen of silver carp and bighead carp. Chin. Sci. Bull. 36: 1825–1828.
Xu Bohai, Yin Zhan, Wu Yushen and Cai Taozhen, 1993. Studies on the taxonomy of pathogenic bacteria of the bacterial hemorrhagic septicemia in cultured fishes in fresh water. Acta Hydrobiol. Sinica, 17: 259–266.
Ye Xueping, Yang Guangzhi, Luo Yizhi, Chen Yinliang and Chen Zhihong, 1992. Large-scale culture of grass carp cell and virus by using bioreactor. J. Fish. China, 16: 1 –6.
Yin Zhan and Xu Bohai, 1994. Observation of Vibrio fluvialis Biovar III in tissues of infected silver carp (Hypophthamichthys molitrix) using the fluorescent antibody technique. Acta Hydrobiol. Sinica, 18: 95–96.
