Present Situation and Development Measures of River Crab Industry in Nanjing City

Nanjing Institute of Fisheries Sciences, Nanjing 210036, China

Abstract River crab industry plays an important role in agriculture in Nanjing City, Jiangsu Province. In recent years, with the renewal of breeding mode, the breeding of improved varieties and the construction of brand, the river crab industry has made great progress. Taking the aquaculture enterprises and major breeding farmers in the main producing areas of river crab as the main research object, this paper makes a survey on the river crab industry in Nanjing. Based on fishery statistical data and comparison with advanced areas, this paper makes an in-depth analysis on the current situation, existing problems and development measures of Nanjing river crab industry, and it is recommended to make full use of external opportunities and give full play to its own advantages, in order to make Nanjing river crab industry develop healthily and rapidly.

Key words Nanjing City, River crab industry, Present situation, Development measures

1 Introduction

As a big country producing aquatic products, China is rich in fishery resources depending on its natural geographical advantages, in which river crab is an indispensable part of fishery resources[1]. River crab meat is tender and delicious, rich in vitamin A, vitamin B1 and vitamin B2. The content of protein, fat, phosphorus, calcium and iron in crab meat is higher than that of other kinds of fish, egg and meat, so it is deeply loved by consumers. Jiangsu Province is a major province of river crab culture in China[2]. Taking 2016 as an example, the annual production of river crabs in Jiangsu Province was 354 000 t, accounting for 43.6% of the national production. And the output of river crab in Nanjing was stable at about 24 000 t, and the river crab is also the single species with the largest breeding area in Nanjing. Its breeding and production and the tourism industry driven by it have made great contribution to improving the income of fishermen. Based on the field investigation results of aquaculture enterprises and large breeding farmers in the main producing areas of Nanjing river crab, combined with the fishery statistical data of the whole city, this paper analyzes the development status, industrial advantages and main problems of Nanjing river crab industry. In view of the existing problems, this paper puts forward ideas and development measures in order to promote the healthy development of Nanjing river crab industry.

2 The present situation of the development of river crab industry in Nanjing

2.1CulturescaleNanjing has unique geographical advantages and good ecological conditions in the waters of the Yangtze River, which is suitable for the breeding of young and adult river crabs. Since 2011, the aquaculture area of river crabs in Nanjing has basically stabilized at about 25 000 ha, with an output of 24 000 t, accounting for about 37% of the city’s total aquaculture area. It is the single species with the largest aquaculture area in Nanjing. In 2014, total production decreased slightly as a result of the reduction in aquaculture area. In recent years, the scale of river crab culture in Nanjing has been gradually expanded by adjusting the structure of river crab culture and vigorously popularizing and supporting the models of "rice and crab culture" and "crab and perch mixed culture". And about 430 million river crabs were released in 2017, with an average of 17 580 per ha, which was higher than that in previous years.

Nanjing river crab culture is mainly distributed in five agricultural areas: Liuhe District, Pukou District, Jiangning District, Lishui District, Gaochun District. The river crab culture area in Gaochun District accounts for about 55% of the total culture area, and it is the main producing area of river crabs in Nanjing. River crab industry has become the most important agricultural pillar industry in Gaochun District. Its culture mode is mainly the Gaochun model of low-density ecological culture. Gaochun model is famous for its low output, large size, high quality and high efficiency, and has a considerable influence in Jiangsu Province and even the whole country. In 2016, the total output of river crabs in Nanjing was 24 192 t, of which the output of Gaochun District was 14 606 t, accounting for 60.4% of the city’s total output. The production efficiency (output per unit area) in Pukou District, Gaochun District and Liuhe District is higher than the average level of the whole city, and the overall culture level is high.

2.2NewvarietiesIn recent years, improved river crab varieties such as Changjiang No.1, Changjiang No.2, Nuoya No.1 and Jianghai 21 have been effectively promoted in Nanjing. Among them, Changjiang No.1 and Changjiang No.2 bred by Jiangsu Freshwater Fisheries Research Institute are the most widely popularized. In recent years, the city has an annual output of more than 150 million crabs (standard crab species) of Changjiang No.1 (annual breeding) or Changjiang No.2 (biennial breeding). In 2016, a total of 10 500 kg of megalopas of Changjiang No.2 were released by Qingsong Cooperative Association and Gubai Aquaculture Farm. More than 15 000 kg of megalopas of Changjiang No.2 were released in Nanjing, and more than 120 million crabs of Changjiang No.2 were bred. The promotion area of Changjiang No.1 and Changjiang No.2 in Gaochun District has reached more than 6 700 ha, accounting for 50% of the total aquaculture area. The application of ecological breeding technology in soil pond has further laid a technical and material foundation for the large-scale popularization of new species of river crab.

2.3NewmodelGaochun mode is the main mode of river crab culture in Nanjing. Through the continuous development, improvement and upgrading of Gaochun model by scientific research institutes and aquaculture farmers, a variety of ecological and efficient river crab culture models have been developed on the basis of Gaochun model. At present, river crabs are mostly mixed with green shrimp,Odontobutisobscurus, mandarin fish,etc., in order to improve production efficiency, and are especially combined with the new model of Taihu No.1 green shrimp culture, jointly developed and promoted by the Freshwater Fisheries Research Center of Chinese Academy of Fisheries Sciences and Nanjing Institute of Fisheries Sciences. The benefit of river crab culture and the ability to resist market risk have been greatly improved. The proportion of river crab culture mixed withOdontobutisobscurusculture has been increasing in recent years.Odontobutisobscurushas no mature culture technology at this stage, the market is in short supply and the price is high, which has become a stable source of income in the process of river crab culture. Under the market demand and the continuous innovation efforts of scientific research institutes, new culture models such as "mixed culture of river crab and perch" and "mixed culture of river crab and crayfish" have been developed one after another, and the river crab aquaculture industry in Nanjing has been developing continuously.

2.4NewtechnologySince the large-scale application of ecological breeding technology in soil pond, the yield of megalopa of river crab has increased nearly 10 times. This has laid a technical foundation for the large-scale popularization and application of new species of river crab. In the process of breeding crabs in soil ponds, the risks existing in previous breeding can be solved to a great extent by combining the techniques of temperature and time control and starter feed cultivation. In 2016, the market scale of Changjiang No.2 megalopa continued with Changjiang No.1, and increased slightly. In the aspect of river crab culture, new technologies such as water plants collocation and planting, whole-process compound feed for ecological breeding, precocious crab control, batch cultivation of young crabs, summer temperature control and grass protection, and ecological regulation of water quality have been continuously developed and improved. With the continuous improvement of the technical system of river crab culture, many problems existing in the process of river crab culture have been solved one after another.

3 Problems in the development of river crab industry in Nanjing

Affected by the natural environment, market changes, funds and other factors, there are a series of problems in the development of Nanjing river crab industry. This has affected the sustained and stable development of the river crab industry, which is in urgent need of breakthrough and solution.

3.1ThecostofbreedingisonthehighsideTake Gaochun District as an example, the rent of river crab ponds is basically more than 15 000 yuan/ha, and the rent of some ponds is as high as 30 000 yuan/ha. In 2016, the average price of young crabs in Gaochun area was close to 1 yuan per crab, and the cost of breeding was significantly higher than that in other areas. At the same time, in the process of using Gaochun model to cultivate river crab, feeding a large amount of animal bait makes the feed cost relatively high. Therefore, in terms of cost, there is a lack of competitive advantage.

3.2ThescaleoftheindustryisnotlargeThe breeding area and distribution area of river crabs in Nanjing have been basically fixed, accounting for about 6.7% of the total area of the province. Restricted by the total surface area suitable for river crab culture, in terms of the scale of river crab culture, Nanjing is at the middle level of the province, and the culture area is less than 50% of that in Taizhou, Suqian and other areas.

3.3TheresearchondiseasecontrolisnotdeepenoughIn recent years, the annual loss of river crab caused by disease is more than 100 million yuan, which has seriously affected the economic benefits of river crab industry. The common diseases of river crab are shell ulcer disease,Balantidiasis, shelling failure, black gill disease, enteritis, trembling disease and so on. For common diseases, there are better prevention and treatment methods. Under normal circumstances, large-scale outbreaks will not be formed, which will do little harm to the whole industry. However, in recent years, it is often reported that the cause of hepatopancreatic necrosis disease is unknown, the incidence is irregular, and there are no clear and effective prevention and control measures[3], which is also a hot topic in the research of aquatic diseases. Due to the weak, unsystematic and simple research on pathogenic mechanism, rapid diagnosis and control drugs of river crab, river crab diseases occur from time to time.

3.4ThecurrentsituationofaquacultureisnotinlinewiththepolicyguidanceAt present, more and more attention has been paid to the problem of water environment. As a breeding species, river crab directly uses natural bait such as chilled fish in the process of culture. It is regarded as a part of the source of water environmental pollution, and it is very difficult to fully use formula feed in a short period of time[4]. The red line of basic farmland is one of the increasingly stringent policies implemented by the country. Some river crab farming ponds are located within the range of basic farmland. Because the economic benefit of grain production is low, the enthusiasm of farmers engaged in grain production is not high, so they turn to engage in river crab breeding. However, with the tightening of policy, the aquaculture ponds in the basic farmland are bound to withdraw gradually, and the scale of river crab farming is bound to be affected.

3.5TheoverallindustrialstructureisunreasonableThe development of the primary, secondary and tertiary industries in Nanjing is extremely uneven, and it is difficult to find traces of the secondary and tertiary industries. It does not give full play to the advantages of the consumer market close to the metropolitan area. This has led to the cultivation of good crabs, but most of the time, they only promote brands such as "Yangchenghu" and do not have a say in the market competition and lack the premium capacity. In terms of brand construction, due to the lack of direct market terminals, the "Guchenghu" brand that Nanjing River Crab is proud of is gradually reduced from a national brand second only to "Yangchenghu" to a regional brand. It is also in danger of being surpassed by brands such as "Hongzehu", "Taihu", "Xinghua" and even "Panjin". This is extremely incommensurate with the huge advantageous background of having China’s first organic river crab, the first well-known trademark of aquatic products, and the first aquatic product of China’s National Geographic Indication. In the process of the fall of the brand, the local government lacks foresight and ineffective guidance to the development of the industry, so it has an unshirkable responsibility.

3.6AdvertisingmeanssuchasfestivalsandparksareamereformalitySince 2001, Gaochun Guchenghu Crab Festival has been successfully held for 16 years, but it still stays in form and does not produce substantial consumption. Compared with hundreds of millions of yuan of river crab sales on the day of the Yangchenghu Fishing Festival, Gaochun Guchenghu Crab Festival had little effect on Nanjing’s river crab industry. Guchenghu Slow City enjoys high popularity, but as far as the current situation is concerned, it does not live up to its name. In particular, it did not play its due role in the promotion of river crab culture in Guchenghu. Today, when the wetland park can be seen everywhere, if it loses its characteristics, it will be marginalized. Guchenghu river crab has lost a good brand promotion platform.

4 Solutions and development measures

In order to promote the development of Nanjing river crab industry and solve the related problems, the targeted measures and development ideas are put forward on the basis of full investigation.

4.1StrengtheningappropriateregulationandcontrolandguidingorderlycompetitionWhen the price of river crab is high and the benefit of breeding is good, the rent of pond also goes up. Although this is the law of the market, when the market is weak and the efficiency of aquaculture is declining, it is often difficult for pond rents to come down. This leads to the expansion of the loss area of the river crab breeding industry, harming the interests of practitioners and the long-term development of the industry. In the process of land transfer, local governments can carry out appropriate regulation and control, guide rational competition, give policy guidance to the maximum price according to the market situation, and control pond rent. Or it can withdraw part of the rent, set up a risk reserve and subsidize it in years of poor production to maintain the healthy development of the industry.

In addition, it should increase the supply of improved varieties, speed up the promotion of compound feed, adapt to the policy demand while reducing the cost, promote the healthy development of the industry, and improve the market competitiveness of Nanjing river crab[5].

4.2StrengtheningbrandconstructionbymakinguseoflocationadvantagesNanjing is located in Shanghai-Nanjing-Hangzhou metropolitan area. Shanghai-Nanjing-Hangzhou metropolitan area is one of the most developed and concentrated areas in China, and its consumption potential is huge. In particular, the consumer demand for high-grade river crabs is strong, and being close to the market is the most favorable condition for the river crab industry in Nanjing. The consumer group of high-grade river crab has higher requirements for the quality and brand of river crab. At this stage, the appeal of the "Guchenghu" river crab brand is still slightly insufficient. On the one hand, we should fully publicize the advantages of the country’s first organic river crab, the first Chinese well-known trademark of aquatic products, and the first aquatic products of China’s National Geographic Indication, and tell a good story. On the other hand, it is necessary to strictly supervise all aspects of the river crab industry to ensure the high quality of the river crab and accumulate brand reputation. Although there is no advantage in the area of river crab farming in Nanjing, after the brand grows, it will attract the surrounding river crab industry to concentrate in Nanjing. Drawing lessons from the experience of Yangchenghu, although the annual output of Yangchenghu crab is 2 000 t, the sales volume is more than 20 000 t, which shows the brand appeal.

4.3ActivelychangingthemodeltoadapttopolicyrequirementsGaochun model has been widely concerned by the industry as an advanced river crab breeding model, but it will be eliminated if it continues walking in the old steps and secludes itself. In recent years, a variety of efficient breeding models have emerged in various parts of Jiangsu Province, which can be used for reference. In terms of bait, increasing the promotion of compound feed and reducing the use of natural bait such as chilled fish is the inevitable trend of river crab culture. To adapt to the new policy requirements ahead of time and accumulate more experience will give you a head start.

Different properties of aquaculture ponds should be treated differently. For the pond for river crab culture, which is allowed by the policy as a culture pond, standardized transformation should be carried out to ensure that electricity, roads, water sources and pond depth meet the requirements in order to meet the needs of efficient culture. For the pond, which is within the scope of basic farmland, pond should be returned to the fields in time, and the comprehensive cultivation and breeding should be carried out on the basis of rice fields.

4.4AdjustingindustrialstructureandguidingindustrialdevelopmentIt is necessary to give full play to the advantages of the consumer market close to the metropolitan area, vigorously develop the three products of river crabs, and comply with the trend of experiential consumption. After raising good crabs, we should also sell them at a good price and really increase the income of practitioners. On the one hand, consumers will not produce effective consumption if they do not have enough time to stay. On the other hand, experience is the most direct means to generate consumer confidence, and the most direct experience for the river crab industry is the pleasure from the tip of the tongue. In view of the pivotal position of Gaochun area in Nanjing river crab industry, the establishment of river crab food culture street in Gaochun area is the most effective cardiotonic agent to break through the bottleneck of Nanjing river crab industry development at the present stage. It is also the only way for Nanjing river crab industry not to be eliminated by the market. With the help of Gaochun Slow City’s popularity and superior geographical location, it is necessary to build a river crab food culture street and upgrade the Slow City characteristic theme at the same time. Under the premise of doing a good job of environmental protection, it will be a win-win situation.

4.5MakingfulluseoffestivalstoservethemarketSince 2000, the Gaochun Guchenghu Crab Festival has been successfully held for 16 years, and it is a valuable platform resource. Only by making full use of the resources can the benefit be maximized. The core of any industry lies in the market, so the key to promoting the development of the industry also lies in the market. All government work related to the river crab industry should be aimed at promoting and expanding the consumer market. Drawing lessons from the advanced experience of Yangchenghu Fishing Festival and Xuyi Lobster Festival, the ultimate goal of developing Gaochun Guchenghu Crab Festival is to expand the market and promote consumption. While doing a good job in publicity, it is necessary to provide a good trading environment during the festival. It can draw lessons from the agricultural carnival to make it a festival for farmers and a grand gathering for citizens, make it a river crab feast for consumers, rather than just a formal ceremony attended by relevant leaders.

4.6GivingfullplaytothefunctionoftheparktoattractconsumerstostayGaochun District has Gaochun Slow City, Yangjiang Modern Agricultural Demonstration Park and other well-known parks on the banks of Gucheng Lake. In particular, Gaochun Slow City has a high reputation both inside and outside the province. However, as far as the current situation is concerned, it has not played its due role in the promotion and construction of the Guchenghu brand, and there are no business projects that can attract consumers to stay. In the case that consumers do not have enough time to stay, it is very difficult to realize the culture and brand promotion of Guchenghu river crabs. It is suggested that the local government and agricultural authorities should focus on the cultural brand of river crabs in the positioning of Gaochun Slow City, rather than just as a wetland park. Otherwise, the loss of characteristics will make it difficult to impress consumers, and it will not be attractive enough to attract consumers to spend. While promoting the river crab culture imperceptibly in the park, interactive experience services should be increased.

4.7AdheringtoecologicalaquacultureandmaintainingenvironmentalresourcesGaochun model, which is famous for low-density ecological breeding, has played an indelible role in the development of Nanjing river crab industry, but Gaochun model is not perfect. With the increasingly stringent requirements of environmental protection and the requirements of healthy culture with controllable quality, the unprocessed natural baits such as chilled fish used in river crab culture must be gradually replaced by compound feed. It is necessary to vigorously develop the compound feed technology of river crab, speed up the promotion of the whole process of compound feed culture, and gradually reduce or even eliminate the use of natural bait such as chilled fish, which will be the only way to comply with the development of the policy. The price of river crab with large size and small size in the market often fluctuates. Especially in 2014, large-size river crabs have no obvious price advantage. This causes many crab farmers to increase their stocking capacity, and change from the pursuit of size to the pursuit of yield. The increase of stocking and yield will lead to the increase of feeding and diseases, thus increasing environmental pressure, which is not conducive to the healthy development of the industry. Ecological environment is the basis for the survival of river crab industry, so to maintain a good ecological environment is beneficial to maintaining the most important resources for the development of river crab industry.

4.8StrengtheningdiseasemonitoringandincreasinginvestmentindiseaseresearchStrict control of the use of inputs, maintenance of water plants and water quality has become the only possible and effective measure to prevent hepatopancreatic necrosis disease at the present stage. Hepatopancreatic necrosis disease is like the sword of Damocles hanging over the heads of all river crab farmers. The key to really solving the problem lies in finding the law and reason of the disease. It is necessary to increase the collection of statistics of disease prediction, find the law of disease, make use of the advantages of scientific research, increase investment in research, clarify the pathogenesis of diseases, and achieve targeted and effective prevention and control.

4.9OptimizingtheculturemodetoimprovetheculturebenefitThe mode of mixed culture and combined culture of river crab with other species has been constantly accumulated and updated in the innovation of scientific research departments and the practice of aquaculture practitioners. The models of "river crab and green shrimp culture", "river crab and mandarin fish culture", "river crab andOdontobutisobscurusculture", "river crab and crayfish mixed culture" have emerged everywhere, and "river crab and perch mixed culture" has become a new hot spot in river crab culture. Interculture or mixed culture has not only become an important source of economic benefits in river crab culture, but also effectively balanced the risks caused by market fluctuations. There is no lack of advanced ideas and experience that can be absorbed and used for reference in a variety of river crab culture models emerging in various places. It is necessary to actively learn and sum up advanced experience and constantly improve the river crab culture model and technical system. However, as far as Gaochun area is concerned, most of the river crab culture ponds are transformed from rice fields, and the water depth of the ponds is generally less than 1 m. This is disadvantageous to the adjustment of river crab culture mode, insufficient water depth can lead to the lack of high temperature resistance in river crab culture, and there is a certain risk of river crab culture. In addition, due to the tightening of the basic farmland policy, ponds within the scope of basic farmland need to be returned to the fields, and in accordance with the "comprehensive cultivation in rice fields" model advocated by the state, rice and crab cultivation can be carried out to compensate for the reduction of river crab culture area. For ponds that are not within the scope of basic farmland, the government should lead the standardized transformation of ponds to meet the needs of multi-mode and high-benefit culture, and at the same time improve the anti-risk ability of river crab culture.

4.10IncreasinginvestmentinmechanizationandintelligenceAt present, the degree of mechanization and intelligence of river crab culture still lags far behind other agricultural industries, which consumes a lot of manpower in aquatic plant management, baiting and other links. With the rise of labor costs, contradictions have become increasingly apparent, and due to the arbitrariness of human factors, it is difficult to achieve standardized operation. In fact, this is inseparable from the current situation of river crab farming. For example, at the present stage, it is difficult to realize mechanized operation by feeding natural bait in the process of river crab breeding, so strengthening the promotion of whole-process compound feed is also the premise of realizing mechanized feeding. Because of the diversity and complexity of aquaculture ponds, the development of miniaturized machinery which is easy to operate and transport is also a necessary condition to popularize mechanized production in an all-round way.

Due to the good development of river crab industry and high overall profits in Gaochun District, its broad development prospects are promoting the younger generation of aquatic workers to gradually move towards the foreground, so the aging problem of aquatic workers is not very prominent. The younger generation of fishery workers have some weaknesses, such as inexperience, failure to endure hardships, but they also have the advantages of high acceptance of new things, and are easier to master intelligent operation. This has a very positive effect on the intelligent development of the river crab industry. At the same time, we should increase investment in intelligent fishery research in scientific work and increase intelligent promotion at the policy level. Under the guidance of standardized operation rules, it is necessary to realize real-time monitoring of aquaculture water quality, monitoring of the use of inputs, prediction of market price trend, automatic operation in the process of pest prevention and control, and so on. This will make the product quality more controllable and realize the standardization of the whole industry.

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