my country’s freshwater bass industry development report
By: Date: 2021-02-28 Categories: industrynews Tags: ,
  Introduction

   The main freshwater perch farmed in my country are the largemouth bass Micropterus salmoides, the jewel perch Scortum barcoo, the zander Lucioperea lucioperca, and the perch Perca fluviatilis. They are all perch-shaped. Among the most important species of fish, largemouth bass currently has the most farming areas and the largest farming scale. Largemouth bass, commonly known as California bass, belongs to the genus Perciformes, Perciidae, Sunfish, and Black bass. It is naturally distributed in freshwater basins from central and eastern North America to northern Mexico. It is one of the most important species of game fish in North America. Largemouth bass is a wide-temperature fish, which has the advantages of fast growth, easy catch, delicious meat and no intermuscular spines, and is very popular among farmers and consumers. In the late 1970s, my country’s Taiwan region imported largemouth bass from abroad. In 1983, the artificial breeding was successful, and it was introduced into Guangdong Province, where it was first cultivated in Shunde, Guangdong. In the early stage of industrial development, farming was done by manually cutting iced fish into small pieces or feeding them with meat slurry. With the popularization of mechanization, the difficulty of feeding has been reduced. In addition, the high market price of perch has gradually attracted more farmers to join. . In recent years, due to the breakthrough and application of artificial compound feed for largemouth bass, the maturity of cold chain transportation technology and the expansion of the consumer market, the breeding area and scale of largemouth bass have expanded rapidly, and the main production areas have expanded from coastal provinces and cities to inland Multiple provinces and cities. In 2018, the national freshwater bass farming production reached 432,100 tons, and it is expected to reach 500,000 tons in 2019. Guangdong Province is my country’s largest freshwater bass farming province, with a farming area of ​​about 100,000 mu and an annual farming output of more than 250,000 tons, accounting for about 60%of the country’s total output. Freshwater bass farming in Jiangsu and Zhejiang provinces has developed rapidly in recent years. The total output of the two provinces in 2018 was about 90,000 tons, accounting for 21%of the country’s total output. The provinces with production of more than 10,000 tons include Jiangxi, Sichuan, Hubei, Fujian and Henan. Freshwater bass has become the fastest growing species of freshwater aquaculture fish in my country in recent years, the market price is relatively high and stable, and the economic efficiency of aquaculture is better.

  1. Current status of industrial development< /div>


   (one) seedlings

  1, scale layout

   As the scale of largemouth bass farming continues to expand in my country, the demand for seed is also increasing. The national annual demand for largemouth bass seedlings is about 50 billion. Largemouth bass seed production is mainly concentrated in Guangdong, Zhejiang, Jiangsu, Sichuan, Hubei Province and Chongqing City.

  Guangdong Province is the largest seed production area for largemouth bass. In addition to meeting local breeding needs, it is also sold throughout the country. The seedling production accounts for about 60%of the country. the above. The seedling production areas in Guangdong Province are distributed in Foshan, Jiangmen, Guangzhou, Huizhou and Zhaoqing. Among them, Foshan is the main producing area, and its output accounts for about 60%of Guangdong’s total seedlings. There are no less than 20 Miao enterprises with an annual output of more than 500 million splashes in Guangdong. Since 2017, a number of factory seedling workshops have been built.

   Jiangsu and Zhejiang provinces have also carried out largemouth bass seed breeding in recent years. The largemouth bass seed breeding areas in Jiangsu Province are mainly in Wujiang District, Xiangcheng District and Wuzhong District of Suzhou City. In 2019, there are 8 licensed seedling farms, producing about 1.6 billion seedlings. The breeding of largemouth bass seedlings in Zhejiang Province is mainly concentrated in Huzhou City, Jiaxing City and Hangzhou Yuhang District, and earth ponds are mostly used for fry standardization. Since 2018, some enterprises in Zhejiang Province have begun to explore the technology of factory-based circulating water standard seedlings, including the technology of cultivating early seedlings and all-season seedlings through the industrial circulating water system.

   In general, largemouth bass seedling farms are large in number and small in scale, and most seedling farms mainly produce standard thick seedlings. The breeding of largemouth bass mostly adopts the methods of spawning, hatching and breeding in earthen ponds; Jiangsu and Zhejiang mostly adopt the production method that parents enter the earthen ponds with covered greenhouses at the end of the year (December) to strengthen cultivation, March 20 of the following year Seedlings emerge around. However, since pond seedlings are susceptible to changes in temperature and natural feed abundance in the water body, the success rate of seedling raising is low (10-20%). In recent years, Guangdong, Zhejiang, Jiangsu, Sichuan, and Guangxi have adopted the factory-based circulating water nursery method, which has solved the problems of oxygen supply and water quality treatment. It is convenient and controllable, so it can effectively improve the survival of seedlings. Rate (40-50%). At the same time, the anti-season seedling breeding technology in Sichuan, Jiangsu, Zhejiang and other places has also been successful. Through temperature and nutrition regulation, all-season breeding and seedling cultivation can be realized, which can partially meet the needs of annual breeding. In addition, early spring seedlings are used in the north and the early spring fish seedlings are cultivated through supporting thermal insulation greenhouses to shorten the time for breeding and marketing.

  2, industrial benefits

   The national annual output of largemouth bass is more than 30 billion, with an output value of more than 170 million yuan; the standard crude seedling is nearly 3 billion, with an output value of more than 1.7 billion. Guangdong will produce 25-30 billion largemouth bass in 2017-2019, with an output value of 125-150 million yuan; an annual output of 1.75-2 billion standard crude seedlings, with an output value of 1.4-1.6 billion yuan. In the past three years, Jiangsu has produced 1.8-2.2 billion water splashes, with an output value of 8.1 million-12 million yuan; an annual output of 60-70 million standard crude seedlings, with an output value of 30-35 million yuan. In the past three years, Zhejiang Province has produced 7-950 million water flowers with an output value of 7-9 million yuan; an annual output of 1 to 142 million standard crude seedlings, with an output value of 85.5 million yuan.

  (2) breeding

  1, scale layout

   At present, the total production of freshwater bass farming in my country is more than 400,000 tons (Figure 1). The main producing areas include Guangdong, Zhejiang, Jiangsu, Jiangxi and Sichuan provinces. Five The province’s freshwater bass farming production accounts for about 90%of the national freshwater bass farming production. Guangdong is the province with the earliest freshwater bass farming, the largest farming area, and the highest production in China (Table 1). The freshwater bass farming output is about 60%of the national freshwater bass farming production. The farming area is about 100,000 mu, which are concentrated in Shunde, South China Sea, Sanshui, Gaoming, Zhongshan, Jiangmen and other places, the yield can reach about 3 tons; Zhejiang freshwater bass farming is mainly distributed in Huzhou area, with a breeding area of ​​more than 40,000 mu; Jiangsu freshwater bass farming is mainly concentrated in Nanjing and Suzhou and other regions have a breeding area of ​​more than 30,000 mu; Jiangxi Province has more than 20,000 mu of freshwater perch breeding; Sichuan’s freshwater perch breeding is mainly distributed in Chengdu, Mianyang, Deyang and Panzhihua, with a breeding area of ​​more than 10,000 mu.
my country’s freshwater bass industry development reportimage
  Figure 1. my country’s perch farming production from 2004 to 2018
my country’s freshwater bass industry development reportimage(1)< br/>
   The total production of freshwater bass farming nationwide in 2018 was 432,100 tons, a decrease of 5.43%over the previous year. The total production of freshwater bass farming accounted for the country’s total freshwater farmed fish production. 1.70%, an increase of 0.13%over the previous year. There are 26 provinces, autonomous regions and municipalities in the country that produce freshwater perch. The main producing areas are Guangdong, Zhejiang, Jiangsu, Jiangxi and Sichuan. The freshwater perch farming output is 25.84, 5.10, 3.97, 1.74, and 15,600 tons, each accounting for the country’s freshwater. 59.81%, 11.79%, 9.19%, 4.04%, 3.61%of the total production of perch farming.

  Industrial benefits

  (1) Economic Benefit Analysis

   freshwater perch is mainly cultured in ponds. The seed is mainly sourced from Guangdong. The price of water splash is about RMB 70-80/10,000. The main adult fish production areas include Guangdong, Jiangsu, Zhejiang and Anhui provinces. The Guangdong area starts stocking in late March each year, and Jiangsu, Zhejiang and other areas start stocking in April and May, with an average stocking density of 3000-5000 fish/mu (The seed size is 6-7cm/tail, the price is about 1.0 yuan/tail), the breeding period is 12-15 months, the harvest size is more than 400g/tail, and the average output is 1500-2500kg/mu. Based on the follow-up and field survey data of farmers in the main producing areas of perch, this report analyzes the economic benefits of adult fish farming in perch ponds.

  1) Cost analysis

   Feed fees, seed fees, pond rental fees, and labor costs are important components of production costs, accounting for 67.35%, 2.04%, 5.61%, and 6.12%, water and electricity fees, fishery and medicine fees, fishing fees, depreciation fees and other expenses accounted for 4.59%, 4.08%, 1.53%, 4.08%and 4.59%of the total cost respectively. Feed costs account for the largest proportion of production costs. The price of compound feed for freshwater perch has continued to decline in the past two years. In 2019, the feed price is about 9,800 yuan/t, the feed coefficient is 1.2-1.5, and the cost per kilogram of perch feed is about 11.7-14.7 yuan, plus pond rent. , Water and electricity, labor, fishery medicine, etc., the cost is 19-21 yuan.

  2) Benefit analysis

  Commercial freshwater bass fish prices fluctuate regularly. The temperature is high from June to September each year, the amount of fish in storage is small, and the price is higher. The average pond price is about 46-56 yuan/kg, January-March and November-December are relatively low prices, and the average Tangkou price is about 30-40 yuan/kg. The breeding density in Guangdong is high, with an average output of 2000-2500kg/mu. The average output of other areas is 1000-1500kg/mu, and the average price is 36 yuan/kg. The cost per unit area in Guangdong is 19600-29400 yuan/mu, and the net profit per unit area is 16400-24600 yuan/mu; the cost per unit area in other areas is 39200-49000 yuan/mu, and the net profit per unit area is 32800-41000 yuan/mu. The profit margin of aquaculture costs 83.67%.

  (2) Ecological benefits< /div>


The key technologies such as artificial breeding of freshwater bass and feed domestication have made many major breakthroughs in production and application. The breakthrough of large-scale seedling breeding technology has met market demand. Variety improvement and new variety research and development have provided guarantee for the source of sea bass fry and industrial development. Compound feed replaces the cultivation method of chilled feed, reduces the consumption of marine fishery resources, and effectively reduces the pollution of aquaculture tail water, with significant ecological benefits.

  (3) Social Benefits

  Freshwater bass has become an important economic fish in freshwater in our country. Its delicious meat and no intermuscular spines are very popular with consumers. In 2004, the Ministry of Agriculture listed perch as a pollution-free food in relevant industry standards. After analyzing the polyunsaturated fatty acid composition of seabass, the British health department also included seabass as a pollution-free food and became a source of high-quality protein in the diet of residents. While enriching consumers’ food baskets and satisfying consumers’ demand for high-quality protein, the perch industry has also played a vital role in increasing farmers’ income and solving farmers’ employment issues. In 2018, my country’s perch production reached 432,100 tons, accounting for 1.70%of the country’s total freshwater aquaculture fish production. The aquaculture area covers 26 provinces (municipalities and autonomous regions) with an output value of over 10 billion yuan. Radiation drives circulation, processing, animal protection, and feed. Other production links have made important contributions to solving the employment of farmers, increasing the income of cooperative farmers, and promoting the increase of people’s income and prosperity.

  (三) Diseases

   In recent years, the common pathogens of largemouth bass farming in my country mainly include viruses, bacteria and parasites.

  viral disease

   largemouth bass viral diseases mainly include viral ulcer disease, spleen and kidney necrosis and rhabdovirus disease. Viral ulcer disease is mainly caused by iridescent virus infection of the genus Ranavirus. The water temperature of the disease is 25~30℃, which mainly harms adult fish. The course of disease is long and fulminant deaths generally do not occur. Spleen and kidney necrosis is caused by the iridescent virus of the swollen virus genus. It is most likely to spread when the water temperature is 28~30℃, and it mainly harms adult fish. The infection often shows fulminant death. Rhabdovirus disease is caused by rhabdovirus infection. It is most susceptible to disease when the water temperature is 25~28℃. Especially when the water temperature suddenly rises or falls, it is easy to cause the disease. The disease mainly harms the fry, spreads fast, and kills. high. The virus disease of largemouth bass is basically similar to that of mandarin fish. There is no effective treatment method at present, but the prevention and control measures and countermeasures of virus disease in mandarin fish farming can be used for reference.

  bacterial diseases

   Bacterial diseases of largemouth bass mainly include Flavobacterium columnar disease, Aeromonas disease, Nocardia disease, etc. Flavobacterium columna is caused by the infection of Flavobacterium columna. The water temperature of the disease is 25-28℃, which can be harmful to fish species and adult fish. Largemouth bass cultured in high density or cages is more susceptible to disease. April to May is the period of high incidence of disease. , The mortality rate can reach 60%. Enteritis and hemorrhagic disease is caused by Aeromonas infection. The water temperature of the disease is about 30°C. The infection can be caused at all stages of breeding. It is mainly related to the intake of unclean food. Once the infection occurs, it can lead to fulminant death and high mortality. Nocardiosis is caused by Nocardia amberjack infection. The water temperature of the disease is 25-28℃, which mainly harms adult fish. Nocardiosis is a chronic disease with a long incubation period and is difficult to be detected. Therefore, its morbidity and mortality are both Higher, and seriously affect the commercial value of adult fish. Except for nocardia disease, other bacterial diseases can be controlled by external consumption and internal administration; in addition, the prevention and control of parasitic diseases should be strengthened to reduce secondary bacterial infections.

  parasitic diseases

   largemouth bass parasitic diseases mainly include trichosanthes, oblique tube worms, dactylus ringworms, branchworms, anchor head worms, etc. Trichoderma, oblique tube worm, dactylus ringworm, etc. are more harmful to seedlings, which can cause gill filament damage and cause a large number of seedling deaths. The branchworms and anchor heads mainly harm the adult fish. They attach to the host’s body surface, gills, and mouth, etc., and can cause death when they are severely parasitic. The prevention and control of parasitic diseases should not only diagnose the pathogen and use symptomatic drugs, but also regulate the water quality of the breeding pond.

   (four) feed

   With the advancement of largemouth bass feed preparation technology and the enhancement of environmental protection awareness, the proportion of compound feed used in largemouth bass breeding has increased in the past three years. The range is increased, and the use of chilled fish feed is correspondingly reduced. The production and sales volume of compound feed increased from 30,000-40,000 tons in 2015 to about 250,000 tons in 2019, and the output value was close to 3 billion yuan. In 2019, the amount of compound feed reached 55-60%of the market’s available capacity, and it is expected to show a steady upward trend in the future. At present, there are more than 30 manufacturers involved in the production of special compound feed for largemouth bass in the country, mainly distributed in the main producing areas of largemouth bass, namely the Pearl River Delta and the Yangtze River Delta. Among them, the amount of compound feed for largemouth bass produced in the Pearl River Delta region is about 180,000 tons, accounting for about 72%of the national output; the amount produced in the Yangtze River Delta region is about 50,000 tons, accounting for about 20%of the national output ; The output in other regions is about 20,000 tons, accounting for about 8%of the national output. According to the ranking of enterprises (or groups), there are only 1-2 companies with an annual production and sales of more than 40,000 tons of special compound feed for largemouth bass; about 4-5 companies with an annual production and sales of more than 20,000 tons; and most The annual production and sales volume of the company is about 5,000 tons.

  (5) Circulation and processing

   There are currently about 120 freshwater perch circulation companies, mainly in the Pearl River Delta. In 2017, the output of freshwater bass in Guangdong Province was 296,600 tons, accounting for 64.91%of the country’s total output, and the circulation ratio was over 90%. Calculated on the basis of 90%of the circulation, the transaction volume of Guangdong freshwater bass in 2017 was 266,900 tons, with a transaction volume of about 8 billion yuan. In 2018, the output of freshwater bass in Guangdong Province was 258,400 tons, accounting for 59.81%of the national total, with a transaction volume of 232,500 tons and a transaction volume of about 7 billion yuan. It is estimated that the trading volume of Guangdong freshwater bass in 2019 will reach 250,000 tons, with a trading volume of about 7.5 billion yuan. In 2017, the output of freshwater perch in Hubei Province was 0.99 million tons, accounting for 2.17%of the total output of the country. There were about 20 aquatic products circulation companies. Calculated based on the proportion of circulation accounting for 90%of the total output, the transaction volume of freshwater perch in Hubei in 2017 was 0.89 million tons. , The transaction volume is 270 million yuan. In 2018, the output of freshwater bass in Hubei Province was 12,300 tons, accounting for 2.85%of the country’s total output. The transaction volume was about 11,000 tons, and the transaction volume was about 330 million yuan. It is estimated that the trading volume of Hubei freshwater perch in 2019 is about 15,000 tons, and the transaction volume is about 450 million yuan. In 2017, the output of freshwater bass in Hunan Province was 3,600 tons, accounting for 0.79%of the country’s total output. There were more than 10 aquatic products distribution companies. Calculated by the proportion of circulation accounting for 90%of the total output, the trading volume of freshwater bass in Hunan in 2017 was about 3,200 tons. , The transaction volume is about 95 million yuan. In 2018, the output of freshwater bass in Hunan Province was 3,700 tons, accounting for 0.87%of the country’s total output. The transaction volume was about 3,300 tons, and the transaction volume was about 100 million yuan. It is estimated that the trading volume of Hunan freshwater perch in 2019 is 5,000 tons, and the trading volume is about 150 million yuan.

  (6) Market consumption

  1, market and price changes

  (1) Price change trend

   From 2017 to 2019, the average annual price of freshwater perch in China was 30.52, 27.23 and 29.49 yuan/kg, respectively. Tangkou price changes throughout the year have obvious seasonal changes. In the first four months of each year, the price remained relatively stable. From May to September, the price gradually rose to the highest price in the whole year. After October, the price began to fall until the beginning of the year due to the concentrated harvest at the end of the year. The changes in the monthly pond price of freshwater perch in my country from 2017 to 2019 are shown in Figure 2.
my country’s freshwater bass industry development reportimage(2)< br/>
  2, consumption intention and structure analysis

   (1) Analysis of consumer preference for bass in different regions

   bass acceptance. In the survey sample, there are fewer consumers who have never heard of bass, accounting for 3.84%of the total; who have heard of it but have not purchased 25.49%of the total; consumers who have purchased 70.67%. Among consumers who have never heard of bass, consumers in Tibet, Xinjiang, and Qinghai account for the highest proportions of the total local sample, respectively 19.23%, 9.38%, and 9.09%; among consumers who have heard of it but have not purchased Consumers in Xinjiang, Tibet, and Yunnan accounted for the highest proportions of the total local sample, with 53.13%, 50.00%, and 44.76%respectively. Among consumers who have heard of and purchased, consumers in Shanghai, Beijing, and Fujian accounted for The proportion of the total local sample is the highest, 87.18%, 81.73%, and 79.81%respectively. Most consumers have bought bass products. Consumers in the eastern region have a higher acceptance of bass (such as Shanghai, Beijing, Fujian), and consumers in the western region have the least acceptance of bass (such as Tibet, Xinjiang, and Qinghai).

  Product purchase form. Among the main forms of products purchased, fresh and live products accounted for 77.74%, chilled products accounted for 12.81%, frozen products accounted for 6.67%, semi-finished products accounted for 1.64%, and ready-to-eat products accounted for 1.14%. It can be seen that the main consumption form of perch products is still Mainly live and fresh products. Provinces (cities, districts) where the proportion of consumers with fresh and live products as the main form of consumption exceeds 60%, including Shanghai, Jiangxi, Zhejiang, Henan, Jiangsu, Guangdong, Fujian, Shaanxi, Shanxi, etc.; fresh perch is second only to The second largest form of consumption of fresh perch, the proportion of consumers in various regions with ice fresh perch as the main form of consumption is 2%-20%, of which more than 10%of the provinces (cities, districts) include Tianjin, Liaoning, Shandong, Hebei , Beijing, Fujian, Jilin, Heilongjiang, Qinghai, Ningxia, Inner Mongolia, Shanxi and other places.

   product purchase volume. Perch is not the main species of aquatic products consumed by consumers, and its consumption accounts for less than 30%of the total purchases of aquatic products. Consumers in the east account for 10-20%of total aquatic product consumption, 10-30%in the middle, and 5-20%in the west.

   product price evaluation. The consumers who think that the price of bass are average accounted for 57.73%, the higher accounted for 31.31%, the lower accounted for 8.18%, the very high accounted for 2.11%, and the very low accounted for 0.67%. Consumers in the eastern, central and western regions have a more consistent evaluation of the price of perch, thinking it is fair or high.

   (2) Analysis of different consumer groups’ consumption preferences for bass

  Product purchase form. Fresh perch is the most common form of perch consumption. Young people (20 years old and below) have the lowest demand for fresh bass, and their consumption patterns are more diversified. Consumers aged 31-40 most prefer fresh bass, which is related to their existing fixed consumption habits. Consumers aged 20 and below who use live bass as the main form of consumption account for 43.96%of consumers in this age group, 21-30 years old for 54.77%, 31-40 years old for 60.73%, 41-50 years old for 58.73%, 51 Years old and above accounted for 48.80%. High-income consumer groups prefer fresh and live aquatic products. Consumers with a household monthly income of 5,000 yuan or less, whose main form of consumption is fresh perch, accounted for 43.35%of consumers of this income level, 5001-10000 yuan for 53.82%, 10001-15000 yuan for 57.55%, and 15001-20000 yuan for consumers. 63.71%, 2,0001-30000 yuan accounted for 67.01%, and more than 3,0001 yuan accounted for 63.74%.

   product purchase volume. There is little difference in the amount of bass purchased by consumers of different age groups. Consumers aged 20 and under purchase bass in the proportion of total aquatic products mainly at 10-20%and below 5%. Consumers aged 21-30 are 5%-20%, 31-40 years old. The number of consumers is 5%-20%, the number of consumers aged 41-50 is 5%-20%, and the number of consumers aged 51 and above is 5%-20%. The lower the income level of consumers, the lower the percentage of perch purchases in the total purchases of aquatic products. Consumers with a monthly income of 5,000 yuan or less purchase perch in the proportion of total aquatic products mainly ≤10%, and consumers with a monthly income of 5,000 yuan or more purchase perch in the proportion of total aquatic products mainly concentrated in 520%.

   product price evaluation. Older consumers are less able to pay and are more sensitive to the price of aquatic products. Most consumers aged 20 years and below, 21-30 years old, 31-40 years old, 41-50 years old think that the price of bass is average (38.05%, 41.69%, 41.38%, 40.57%), and most of them are 51 years old Consumers and above believe that the price of bass is higher (36.80%) and 5%-10%(19.20%). The level of income largely affects consumers’ perception of the price of high-quality goods. Consumers of different income levels have average or higher evaluations of the price of perch. The lower the income level, the higher the evaluation of the price.

  Second, technology research and development progress

   (1) Annual technical progress

  1. Cultivation and promotion of fine varieties of largemouth bass

   The Pearl River Fisheries Research Institute of the Chinese Academy of Fishery Sciences acquired the first new largemouth bass variety”Youlu No. 1″ in 2011 after five generations of selection, and its growth With fast speed and low deformity rate, breeding is promoted throughout the country, and the promotion area accounts for 50%of the national largemouth bass farming. In response to the slow growth of largemouth bass in the application of compound feed and the low efficiency of fry conversion and domestication, the largemouth bass”Youperch No. 3″, which is easy to eat compound feed and grows fast, was cultivated through group selection, 2019 Passed the approval of new varieties of aquatic products in 2015, it is expected to further promote the application of compound feed in largemouth bass breeding in my country through the promotion of new varieties, reduce the use of chilled fish, save fishery resources, and protect the aquaculture water environment.

   In addition, in recent years, the characteristic freshwater fish industry system has carried out the selection and breeding of fine varieties of largemouth bass. Freshwater bass germplasm resources and variety improvement posts, engineered breeding posts, Hefei Comprehensive Experimental Station and Anhui enterprises jointly carried out selection and breeding research, using the original species of largemouth bass introduced from the United States in 2016 to carry out largemouth bass”Wanlu No. 1″”Cultivation. The genetic diversity of the introduced population is significantly higher than that of the existing domestic breeding populations. At present, three consecutive generations of breeding have been completed, and the growth speed and disease resistance performance are significantly better than the local breeding populations; in Guangdong, by selecting from multiple breeding populations The basic group, the largemouth bass”Jadefeng” strain, which has been selected and bred for three consecutive generations, also shows obvious growth advantages and high individual uniformity, which is very popular among farmers. The cultivation of fine varieties of largemouth bass can provide more high-quality seed for the rapidly expanding adult largemouth bass breeding industry in my country.

  2. Research and development progress of efficient compound feed formulation technology

   In recent years, relevant scientific research workers, especially the freshwater bass nutrition and feed team of the national characteristic freshwater fish industry system, have continuously improved the largemouth bass nutrition demand database. The scientific and precise nutrition regulation of largemouth bass has basically been realized. Good progress has been made in the main nutrient requirements, feed formulation improvement and processing technology.

   In terms of sugar utilization, due to the low effective utilization of digestible sugar in feed for largemouth bass, excessive intake of digestible sugar can cause a series of harms, so Strictly controlling the intake of digestible sugars is the prerequisite for the development of high-efficiency feeds for largemouth bass. The study found that the appropriate digestible carbohydrate level in the feed for largemouth bass should be less than 10%, which is much lower than the recommended value of international counterparts (less than 19%). Too much sugar in the feed will cause excessive accumulation of liver glycogen, which in turn leads to the deviation of hepatocyte nuclei, vacuolation, and liver damage. Elevated blood sugar levels can stimulate insulin secretion and gene expression to a certain extent, but the activation of the insulin pathway cannot effectively inhibit the gluconeogenesis pathway, which is an important factor that causes its low glucose tolerance. At the same time, it studied the requirements of other important nutrients such as protein, fat, methionine, arginine, vitamin E and vitamin A in the feed for largemouth bass, providing a more comprehensive theoretical basis for formulating high-performance feed for largemouth bass . At the same time, based on the nutritional requirements and metabolic characteristics of largemouth bass, through the screening or improvement of the protein source, fat source, starch source and functional additives of the feed, a series of economical and practical feed formulas have been developed; The processing technology and key equipment that are compatible with the formula and feeding characteristics solve the key technology of low-starch feed processing.

  The above-mentioned technological progress has played a great leading and promoting role in improving the industrial progress of my country’s high-efficiency special compound feed for largemouth bass. It is particularly worth mentioning that some special compound feed products for largemouth bass have been produced and used to prove very effective (feed coefficient is less than 0.9), can completely replace chilled fish feed, and have the advantages of fewer fish diseases. This will promote the transformation of my country’s largemouth bass farming model and help promote the green, efficient and sustainable development of the industry.

   (2) Main recommended mode

  1,”two mornings, one low and one high” breeding mode

   In response to the problems of one-sided pursuit of output, excessively concentrated products on the market and low fish prices in the Pearl River Delta region’s aquaculture production, the national characteristic freshwater fish industry technology system has passed on-site Investigation and put forward the innovative breeding model of”two early, one low and one high” (ie:early release of seedlings, morning market, low density and high efficiency). Early release of seedlings:In the previous December or January of the year, the water flowers were stocked to cultivate fry in a greenhouse. At the end of February or early March, the fry were pulled out and counted, and then passed through the pond to the outer pond for adult fish breeding. Morning market:Set the time for the finished fish to go on the market from August to September. At this time, the finished fish will not be available, and the sales price is at a high level of the year, which is about twice as high as the price at the low level. Low density:Stocking size seedlings (10-15 g/tail) 4500-5000/mu, which is only 50%of the usual stocking density in the area; if the density is too high, the growth rate will slow down, which will affect the expectation of the morning market. High efficiency:After 3 years of this model, more than 6,000 mu of production practice has proved that the average net profit rate can reach 30,000 yuan/mu. The prerequisite (supporting facilities) for implementing this model is to build a plastic insulation shed for early fish breeding. The area of ​​the insulation shed is about one-eighth of the adult fish breeding area.

  2, off-season breeding and”996″ breeding mode

  The production of largemouth bass seedlings in northern regions such as Jiangsu and Zhejiang is limited by the climate. The local seedling cultivation generally starts in April of that year, much later than the Pearl River Delta Regions, therefore, the market rate of finished fishes invested in seedlings that year was low, generally only about 40%, and the price of fish was also low. The remaining pond fish must go through the winter, and continue to breed until June to July in the next year before they can fully reach the finished fish specifications. These so-called”laokou fish” experienced overwintering and the following spring reproduction, and the loss was as high as 40%. Therefore, the low production rate of new fish that year, low fish prices, and the high loss of old fish in the following year are a major disadvantage of the largemouth bass industry in Jiangsu, Zhejiang and the northern regions. In this context, the national characteristic freshwater fish industry system combined with largemouth bass seedling companies after three years of exploration, through the regulation of environmental factors and key nutrients, has achieved a technological breakthrough in the production of largemouth bass in autumn reproduction. The region promotes the application of the”996″ breeding model (ie, the seedlings are released in September, after 9 months of breeding, and the finished fish will be marketed in June of the following year) to solve the bottleneck of seedlings. The advantages of this model are reflected in:(1) the loss of fish species overwintering is relatively small, no more than 20%; (2) the market is staggered, and the price of commercial fish is higher; (3) the benefit is higher than that of spring release. The production method of seedlings is on average about 50%higher. The prerequisite for implementing this model is the supply of autumn seedlings, and the price of autumn seedlings is about 50%higher than that of spring seedlings. However, this model is being favored by aquaculture producers and is expected to be widely promoted in Jiangsu, Zhejiang and other northern regions.

  3, largemouth bass and river crab nest breeding technology

   This aquaculture mode reduces the stocking density of a single species, and uses the different habitat and feeding characteristics of crabs and bass to build a”material-energy” ecological cycle and reduce environmental stress. , Thereby improving the quality, output value and economic benefits of aquaculture products while reducing the risk of breeding.

  Technical focus:Make a reasonable match according to pond depth, aeration conditions, water source conditions, and aquatic conditions. The matching principle is:if the density of river crab is higher, the stocking density of largemouth bass should be appropriately reduced, and vice versa. The stocking density is 400-600 crabs/mu and 800-1200 largemouth bass/mu. Focus on the following tasks:(1) The off-season (early propagation) breeding of largemouth bass, to ensure that the fish fry can reach the stocking specifications when the water temperature is suitable for stocking from March to April; (2) The stocking is based on the feeding point. The center’s temporary nets are enclosed and fed at fixed points and regularly to allow the fry to form a fixed feeding habit (continue to tamed in the big pond); (3) The aquatic weeds in the early stage shall be managed according to the monoculture of crabs, and only bitter grass (noodles) shall be planted in the middle of the pond in the later stage. Grass), keep the water on the surface of the water free to circulate, cover 30-50%of the area of ​​aquatic plants, and arrange the waterway and head to prevent it from growing out of the water. Properly put snails in the early stage of the breeding process to promote the conversion of feces and the ability to purify water quality. Provide natural bait. In recent years, the polyculture model of crab and bass has been demonstrated and promoted in Gaochun, Yixing, Siyang and other places in Jiangsu, covering an area of ​​4,000 mu, with an average benefit of about 5,000 yuan per acre, and good breeding benefits have been obtained.

   (3) Development Trend Analysis

  1. There is a huge demand for high-quality seed

   my country’s largemouth bass consumer market has great potential, and because of the breakthrough and application of compound feed, the breeding area and scale of largemouth bass in my country have continued in the past three years. With the expansion, the demand for high-quality seedlings in various places is also increasing. Several main breeding areas have begun to cultivate seedlings locally to provide local seedlings. Because pond seedlings are greatly affected by climatic conditions and food organisms, factory seedlings and off-season seedlings have attracted a lot of seed producers to try. The technology of factory seedlings and off-season seedlings has made breakthroughs, which has promoted the scale of seedlings. produce.另一方面,种质资源与品种改良受到重视,多地开展大口黑鲈优良品种的培育,通过引进原种、台湾产的苗种以及对当地养殖群体的选育可促进我国大口黑鲈养殖业的健康持续发展。

  2、配合饲料技术有所突破,可满足全程养殖需求,价格有所下调

  大口黑鲈配合饲料突破早期未能满足中后期生长需求、鱼养不大的问题,更多的产家产品可满足大口黑鲈全程养殖的营养需求。虽然配合饲料原料价格上涨,但由于饲料研发技术的提高及市场竞争的原因,大口黑鲈配合饲料的价格可能会逐年下调。饲料品质与适口性、满足生长与代谢需求、饲料转化率等方面仍有提升空间。

  3、健康生态养殖受到重视

  大口黑鲈鱼苗培育早期及驯食转食阶段病害问题较严重,寄生虫、细菌与病毒均有发现,尤其是病毒性病原导致的病害,可导致整批苗种死亡;池塘养成期主要是早春回暖期和夏季高温期大口黑鲈的烂身情况较严重,影响产品上市价格。动保行业推出多种的调水、改底等物理化学类产品以及益生菌类产品,同时养殖者对健康生态养殖的认知也有所提高,注重养殖过程的科学管理,对大口黑鲈的健康养殖以及产品质量安全具有重要意义。

  三、问题及建议

  (一)存在问题

  1、苗种难以满足养殖生产需求

  由于国内现有大口黑鲈养殖群体多经过多年的繁育,近亲繁殖较为严重,遗传多样性较低,亲鱼种质质量有所下降。同时各育苗场的育苗技术参差不齐,导致总体上育苗成活率普遍较低,优质苗种紧缺,优质苗种的规模化生产供应成为大口黑鲈养殖业健康持续发展的首要问题。

  2、养殖过程病害多发

  由于普遍采用高密度养殖模式,加大了水质管理与调控难度,导致各种寄生虫、细菌及病毒性病害问题高发,既影响养殖经济效益也易诱发产品质量安全问题。目前大部分水产动保产品和益生菌类产品还缺乏规范管理,如何实现健康养殖,保证养殖经济效益与产品质量安全,同时减少养殖尾水的排放,是急需探索与解决的问题。

  3、配合饲料产品质量良莠不齐、使用率仍较低

  在大口黑鲈高效专用配合配合饲料推广取得成功的背景下,有些不具备核心技术的饲料生产商也乘势宣传造势,以劣质低价产品打入市场,劣质配合饲料使养殖户蒙受损失。这种恶性竞争的混乱局面大有愈演愈烈的态势,将给大口黑鲈优质高效专用配合饲料的进一步推广应用产生干扰。另一方面,尽管近年来配合饲料产销量大幅度增加,但大口黑鲈养殖过程中冰鲜鱼饲料的使用比例,按养殖产量计算仍占40%以上,全程单独使用配合饲料的养殖面积尚不足总养殖面积的30%。冰鲜鱼的使用所引发的养殖水环境污染、鱼病频发和用药量增多等弊病仍突出。

  4、流通环节整体机械化自动化水平不高

  大口黑鲈流通各生产环节仍较为落后,捕鱼环节使用人工拉网,装卸环节以人工搬运为主,在运输、暂养环节的温控和净水方面仍采用人工换水与加冰。大口黑鲈的流通过程至少使用3项技术,即充氧技术、温控技术和净水技术,其中一项技术的标准水平较低或应用效果较差,其它技术以及综合技术的整体实现都会受到影响。以中长途运输环节为例,主要采用有水保活运输技术,过程中贩运商、运输者等多借助增氧机或液氧罐为活鱼供氧,其上配有氧气输送管道、调节阀门和可视量表,可根据气温、密度等精确调控氧气,避免途中因缺氧而出现鱼死亡;但在温控和净水方面,仍采用传统的人工换水与加冰方式,不仅过程中没有可遵循的换水、加冰等标准操作流程与方法,也难以对水温、水质进行准确测量与控制,进而即使上所述采用的充氧技术符合标准,也可能因温控、水质的不适或变化而导致大量死鱼。

  5、缺乏技术规范和统一的运输标准流程

  大口黑鲈运输的各项指标和方法规定不明确,没有统一的技术规范和流程,运输水平和运输后大口黑鲈的质量参差不齐。

  (二)建议

  1、重视种质资源管理与优化

  需尽快建立大口黑鲈原种种质库,优化大口黑鲈种质质量;加大对大口黑鲈选育种研究的资助力度、加快良种培育,特别是生长与抗病性状的选育;加强大口黑鲈良种场、良种繁育场的规划、建设与支持力度,以及政府的管理力度;建立区域性产业苗种支撑体系,做好亲本质量控制、保存及规模繁育等规划,对苗种的流通进行监管,降低病原的传播。

  2、加大健康生态养殖理念的宣传教育与组织

  大口黑鲈养殖密度较高,特别是广东地区由于高塘租,通常放养密度高达5000-12000尾/亩。虽然通过加大池塘的水深可有效加大养殖水体,但对增氧机的功率与性能要求更大。因此应加大健康养殖与绿色发展的理念宣传教育及科学养殖技术的推广,推广生态健康养殖方式,采用合适的养殖模式与精细管理减少病害,并考虑适时实行放养密度限制,以减少病害的发生及药物使用,保证产品质量安全;要研发创新型养殖模式,改善养殖环境、有效防控鱼病,并避免产品的集中上市,使养殖的社会与经济效益得以大幅提升;推广专业合作社,或“公司+基地+农户”的高效管理模式,使养殖户不仅拥有技术和信息,而且能将养殖技术标准化和规模化,提高养殖效益,也容易形成产销一体化产业,促进产品流通。

  3、开展生态养殖技术的应用推广

  通过发展池塘循环流水养殖、鱼菜共生、轮捕轮放、生态湿地、生物絮团及复合养殖系统等生态健康养殖方式,减少养殖对环境的影响。一方面通过政府对新技术开发和研究给予资金支持,对采用健康生态养殖的养殖户给予政策倾斜,鼓励使用健康生态养殖技术。另一方面不断开展生态健康生态养殖的宣传和培训,使养殖户及时了解和掌握最新的生态养殖方式,转变观念,改变落后的生产模式。

  4、加强对病害的监测防治

  病害问题是影响大口黑鲈产业健康发展的重要因素之一,因此要加强对各种病害的监测力度,开发出快速鉴定病原的技术方法,引导养殖户对症下药,不滥用药,将防重于治的观念灌输到养殖户的日常养殖工作中。

  5、强化人工配合饲料的推广应用

  加强对大口黑鲈营养需求与代谢等基础性研究,解决饲料适口性、提高转化率、满足生长与代谢需求;规范配合饲料的质量标准、加强质量监管,加强地方渔业主管部门对饲料企业的管理,保证饲料品质与养殖者利益,确保水产品质量安全;相关政府部门应尽快出台相关政策法规,以规范配合饲料市场的有序竞争,鼓励大口黑鲈养殖业采用优质高效的配合饲料产品,同时限制或禁止冰鲜鱼的使用;进一步加大对大口黑鲈营养与饲料研究的资助力度,完善相关数据库及相关饲料加工工艺,同时加大研究成果的推广应用力度,为饲料企业提供更多的技术支撑。

  6、做好准备应对市场风险

  由于大口黑鲈养殖以散户为主,抗风险能力低,市场鱼价的波动对养殖效益的影响极大,应根据当地市场行情调整养殖规模与品种结构;加快大口黑鲈加工产品的研发,促进产品的多元化,提高产品附加值,扩大市场需求;养殖过程应注意休药期。加强商品活鱼运输过程的监管防范质量安全风险。

  7、加强行业组织管理与引导

  加强省级和地方水产行业协会的建设,使协会真正起到引导生产、技术支持作用,促进行业协会的标准化管理,加强行业内的自律行为,避免无序竞争,提高协会的凝聚力;搞好水产品信息服务体系建设,强化淡水鲈产业信息服务体系建设,提供及时可靠的成鱼和鱼苗销售市场动态信息;加强渔业合作社建设,引导养殖与市场;提高水产品质量,引导养殖户打造自主品牌;帮助养殖户组建专业合作社,以解决养殖分散、专业水平低、消息闭塞的问题,提高产品质量,提高养殖效益。

  (三)新冠肺炎疫情对淡水鲈产业的影响及应对措施

  2019年底湖北武汉暴发新型冠状病毒肺炎,为有效控制疫情向全国蔓延,各地采取了封路与封村等严格的隔离控制措施,市场交易关停、餐饮歇业,与整个水产业一样,淡水鲈产业也受到很大影响。

  1、新冠肺炎疫情对淡水鲈产业的影响

  (1)淡水鲈的消费端受阻,出现存塘量大、鱼价下跌等问题。淡水鲈的主要市场是餐饮、酒店聚会和家庭聚餐。春节期间是鲈鱼消费量最大的时候,但临近春节爆发的新冠肺炎疫情导致大量酒席、聚餐取消,餐饮行业休业,淡水鲈销售受到极大冲击。与正常年份相比,疫情暴发以来大口黑鲈商品鱼销售量同期降幅约80%,销售价格降幅达20%。预计未来半年,酒席、宴会与聚餐仍将明显减少,大口黑鲈鱼价可能会继续走低。

  (2)正常养殖生产节奏被打乱。疫情早期的“封路”影响淡水鲈的流通,导致无法及时清塘、及时投放鱼苗,因而缩短了养成期,并可能产生上市时间集中的问题,影响来年淡水鲈的养殖生产、产量与效益。 “封路”也导致饲料、渔药等渔用物资以及饲料生产原材料的运输受阻,同时许多外地工人回家过年后无法按时回场(厂),对苗种生产与养殖、饲料厂等的生产均造成较大影响。

  2、新冠肺炎疫情后期的应对措施

  (1)由于各地新冠肺炎疫情与防控措施存在差异,各地淡水鲈的繁育、投苗与养殖、加工和运销等应结合当地情况及时调整生产方式、养殖模式和其它经营管理计划,抓好复工复产工作,尽快恢复正常生产,有效降低疫情对生产的影响。

  (2)继续严抓疫情防控工作,养殖生产企业应主动与地方政府、农业农村及渔业主管部门沟通,完善疫情防控物资器械储备,持续开展场(厂)区环境无害化消毒,严格用工人员疫情检查,减少人员场(厂)区进出频次,实施分组、分散作业,督促人员规范使用防护用品(具)、注意个人卫生、形成良好的生活方式和卫生习惯。

  (3)及时关注国家和地方针对疫情的政策与平台,了解疫情信息、产业政策、金融保险措施和市场资讯,加快淡水鲈压塘问题的解决,利用政府兜底补贴政策,减损止损。鼓励加工企业加大收储淡水鲈,开拓淡水鲈的加工方式(比如制作半成品食材)。及时关注气象信息,做好“倒春寒”防范,保证育苗生产与养殖生产的顺利开展。

  (4)进一步积极发挥国家特色淡水鱼产业技术体系各功能研究室、岗位科学家、综合试验站及示范县区、试验示范基地的科技创新和示范推动作用,因时因地及时调整、完善和发布疫情期间和疫情后期养殖生产关键技术指导方案,从水质调控、鱼苗鱼种培育、病害防治与尾水处理等各环节给予科学指导、技术帮助和适当的物资支持。

  (5)切实推进生产经营管理方式方法的改变,利用5G、互联网、水产物联网、绿色通道等手段,逐步实现装备设施化、生产集约化、管理智能化、市场网络化、产品加工化、场区清洁化、物流便捷化。

  附件1:国际技术研发进展

  大口黑鲈具有广温性、生长快、肉质鲜美及无肌间刺等优点而被广泛引种,现已从原产地北美洲扩散到世界各地,成为各地重要的游钓鱼类或养殖鱼类,支撑着墨西哥、美国与多米尼加等国的捕捞业,也成为中国大陆、中国台湾、墨西哥、意大利和阿尔及利亚等的养殖品种。作为具有重要生态学与经济学意义的鱼类,近年国内外对其种质资源与遗传改良、营养与饲料以及病害等方面开展了相关的研究,并取得一定的进展。

  1、种质资源与遗传改良

  美南伊利诺伊斯大学Adam等(2017)收集大口黑鲈野生群体相关数据建立贝叶斯多层模型,可预测最快上市的群体。快长骨骼肌中IGF I和IGF II的表达低于慢长群体,且后者的表达与体重显著负相关;Zhao等利用GBS测序挖掘大口黑鲈南方种全基因组SNP位点,其中58个SNPs 可100%鉴别亲本与子代(Zhao et al.,2018)。 Li等(2017)分析快长和慢长大口黑鲈肌肉转录组并筛选生长相关基因,鉴定出3个与生长相关的SNP标记;Bai等(2019)综述了大口黑鲈遗传育种和分子标记辅助选择育种技术进展。美学者对波多黎12个水库的遗传分析发现大口黑鲈南方种等位基因分布频率与十年前的估算值一致,南方种基因型占比0.03~0.64,且无北方种基因型(Peterson et al., 2017)。孙成飞等(2019)采用12对微卫星特异性荧光标记引物进行群体间遗传距离分析,显示现阶段中国大口黑鲈养殖群体的遗传多样性已显著下降。美康涅狄格大学Hessenauer等(2017)探讨渔业遗传管理方法,引入从未开发的大口黑鲈群体中的个体,以减轻休闲垂钓带来的种质选择压力。大口黑鲈超微观察发现其为硬骨鱼类Ⅰ型精子,结构与鲈形目其它种有异(乔志刚, 2017);赵小兵等(2017)开展大口黑鲈早繁研究,可与广东完全同步批量供应苗种;Yan等(2019)证实大口黑鲈Dmrt1基因在性别决定和精巢发育中发挥着重要作用。

  2、营养与饲料

  进一步完善了大口黑鲈营养需求数据库,通过摄食生长实验确定了大口黑鲈对蛋白质(Huang et al., 2017;Cai et al., 2019)、脂肪(Huang et al., 2017;Guo et al., 2019)、维生素A(连雪原等,2017)及维生素E(Li et al., 2018)的需求量。确定了饲料中适宜的淀粉源及添加水平(刘子科等,2017),发现淀粉水平的升高显著降低了大口黑鲈的生长性能(Ma et al., 2019),而淀粉水平过高则会导致氧化应激并抑制机体免疫力(Lin et al., 2018)。同时确定了适宜的淀粉种类(Song et al., 2018),豌豆淀粉可以在转录水平有效地提高大口黑鲈胰岛素通路的活力,进而减缓其肝糖原累积(Li et al., 2019a)。饲料中适宜水平的纤维素有助于促进生长性能及肝脏功能的维持(Zhong et al., 2019)。通过高通量测序,剖析了大口黑鲈对糖不耐受的分子机制(Zhang et al., 2019)。适宜的脂肪水平有助于提高生长性能(Guo et al., 2019),饲料脂肪升高会诱导大口黑鲈CPT1基因的表达(宋铭琪等,2019)。饲料中鱼油的氧化会严重损伤大口黑鲈的抗氧化系统,造成氧化应激,进而影响生长性能(Yin et al., 2019)。亚麻籽油的添加可有效降低大口黑鲈的脂肪沉积,显著提高其抗氧化能力(Shi et al., 2019)。在鱼粉替代方面,王孟乐等(2018)发现去皮豆粕分别与玉米蛋白和大米蛋白组成的植物性蛋白质混合物可使大口黑鲈饲料中的鱼粉含量由45%降至30%。普通豆粕、酶解豆粕与发酵豆粕均可替代30.91%的鱼粉(对照组鱼粉水平55%), 且酶解豆粕的替代效果最好(张改改等,2019)。禽肉粉与豆粕的合理配伍可显著提高大口黑鲈摄食率以及饲料效率,替代饲料中60%的鱼粉(对组照鱼粉用量40%)(Ren et al., 2018)。在不影响生长及非特异性免疫等指标的前提下,鸡血浆粉可替代饲料中(鱼粉水平51%)10%的鱼粉(Li et al., 2019b)。饲料中的50%的鱼油可在不影响自身生长健康的情况下被豆油所替代,肉碱的添加有助于维持鱼油替代后机体的健康(Chen et al., 2020)。黄芪多糖及壳聚糖的适量添加显著提高大口黑鲈呼吸爆发活力,溶菌酶活性以及SOD活力从而增强鱼体免疫力及抗病力(Lin et al., 2017)。添加酵母水解物(Zhou et al., 2018; Gong et al., 2019)及抗菌肽(Li et al., 2020)有助于大口黑鲈非特异性免疫以及抗氧化性能的提升。 2.6-二叔丁基对甲酚(BHT)(Yu et al., 2018)、益生菌Grobiotic?-A(Yu et al., 2019)及肉碱(Chen et al., 2019)的适量添加可有效改善大口黑鲈的脂肪代谢以及抗氧化能力。

  3、病害防控

  Ho等(2018)用诺卡氏菌的不同重组蛋白制备亚单位疫苗,发现其具有不同的保护效果。 Chen等根据诺卡氏菌的核糖体蛋白RpsA和RplL、FHA蛋白以及分子伴侣DnaK和GroEL制备DNA疫苗,发现其免疫保护率分别为78.31%、71.08%、79.33%、53.01%和80.71%,对诺卡氏菌病的预防有一定的应用前景(2019;2020)。 Zhang等(2019)用大口黑鲈弹状病毒的无毒株免疫大口黑鲈后用强毒株进行攻毒,发现其相对保护率达到100%,意味着该弱毒株在研发大口黑鲈弹状病毒疫苗上具有广阔的应用前景。袁等(2020)制备了大口黑鲈弹状病毒特异性卵黄抗体,该抗体对大口黑鲈弹状病毒具有明显的中和效果,为后续卵黄抗体作为免疫制剂的应用奠定了基础。