I. Development status of shrimp aquaculture in Zhanjiang City
The city's shrimp farming began in 1974 when it took in the sea area Moji and Longhair prawn seedlings. In 1980, for the first time, 2.08 million mimics and long-haired prawn seedlings were artificially cultivated. In the same year, 7.27 hectares were bred. The average hectare yielded 1,260 kg of shrimp, which made the city's shrimp breeding start.
In 1984, the first introduction of P. ostracodus was conducted in Lianjiang City. The area of ​​cultivation was 0.4 hectares. The average hectare produced 997.5 kilograms of shrimp, and the net profit was 1,060 yuan. This provided the basis for the municipal Party committee to vigorously develop the shrimp industry. Therefore, from 1985 to 1988, there was a “shrimp fever†for the first time, and five acres of contiguous shrimp ponds were constructed, mainly in Leizhou, Lianjiang and Potou. In 1988, the shrimp culture area was 8186.7 hectares and the yield was 3,762 tons, which was 17.95 times and 14.87 times higher than that in 1985 respectively.
In 1989 and 1990, the enthusiasm of the masses of shrimp farming was high, and the farming techniques were gradually improved. The ecological conditions in the shrimp ponds were still relatively good. They should have achieved high yields and high efficiency. However, due to political factors and the country’s monetary tightening at the time, there were “dead shrimps†and “ Starved shrimp, thus making the shrimp industry into the first trough, in 1990 shrimp area fell to 3,064 hectares of shrimp production 2,733 tons.
From 1991 to 1992, with the improvement of social and economic conditions, shrimp production began to pick up for the first time. From 1991, Penaeus ostracodus became the main breed of shrimp farming. In that year, 727.22 million pairs of shrimp seedlings were produced artificially, accounting for the shrimp of the current year. The total number of seedlings is 66.5%, aquaculture area is 5915 hectares, 9,824 tons of shrimp are produced, and 1660.86 kilograms of shrimp are produced per hectare, creating the highest level of historical yield. However, by the second half of 1992, an outbreak of shrimp disease began.
From 1993 to 1994, due to the full spread of shrimp disease, the shrimp industry saw a second trough. In 1994, the shrimp area was 7,671 hectares, producing 5,306 tons of shrimp and producing 69.7 kg of shrimp per hectare.
From 1995 to 1998, there was a second "shrimp fever". In 1996, the area of ​​shrimp farming was 10042 hectares, with a production of 10,194 tons, and 1015 kilograms of shrimp per hectare, breaking the 10,000-ton mark for the first time. In 1997, the area of ​​shrimp farming was 10,666 hectares, with a production of 14,400 tons and 1,350 kg of shrimp per hectare. In 1998, the area of ​​shrimp farming was 13,800 hectares, with a production of 21,200 tons and 1,536 kilograms of shrimp per hectare. For three consecutive years, it has achieved the best level of history. The characteristics of shrimp aquaculture at this stage: First, the interests of the socialist market economy are driven. Although the risk of shrimp farming is large, the breeding cycle is short and can be raised for a few times a year. This is more effective and the enthusiasm of the masses is high. Therefore, the main investors have turned from the past government to production operators, forming a multi-subject main investment pattern. According to the survey, in 1997 and 1998, the city invested nearly 300 million yuan in shrimp raising, of which 95% were self-funded by owners, and an area of ​​more than 50,000 mu was expanded. Second, with the improvement of aquaculture technology, the aquaculture production mode has changed from extensive to intensive. The vast number of aquatic technology cadres and shrimp farmers insisted on exploration, created a semi-closed or closed shrimp farming technology, isolated pathogenic technology with fresh water, high-pot shrimp farming technology, and so on, so that a new way for the shrimp aquaculture industry. Third, the infrastructure for shrimp farming has been strengthened. The city has more than 100 shrimp seedlings and nursery sites with more than 100,000 cubic meters of water. It has two national feed factories (Guangdong, etc.) and an annual production capacity of 30,000 tons. There are also complete processing refrigeration plants and pharmaceuticals. These provide the basic conditions for the development of shrimp farming. The fourth is to increase the socialization of shrimp farming services. In recent years, feed mills have taken the lead and hired shrimp specialists as consultants to form feed, seedlings, drugs, and technology train services to shrimp ponds. They have played a significant role in solving the problems in the production of shrimps and shrimps. Farmers welcome.
The main problems in current shrimp farming: First, shrimp disease still plagues the development of shrimp farming. In recent years, the annual incidence rate is 20-30%, the disease is fierce, and the cause is complex. Most of them are mainly viruses, and the viruses and bacteria are complicated. The medication is invalid. Second, the transformation of aging shrimp ponds is difficult. There are 100,000 mu of aging shrimp ponds in the city. The conditions are poor and the yield is low. Although some of the shrimp ponds were reconstructed and the farming model was reformed, there are still some shrimp ponds that have not escaped the predicament. Third, some newly developed shrimp ponds have a low standard and it is difficult to increase production. Fourth, some shrimp farmers have not kept up with the prevention and control of shrimp disease and their aquaculture management. The training needs to be further strengthened. All these problems must be taken seriously and resolved step by step.
Second, several kinds of shrimp breeding mode
1, high pool breeding
This model was first established in 1991 by the Zhanjiang Fisheries Bureau using open air 0.57 hectares of land in a direct-owned Hongkong shrimp hatchery, releasing 750,000 pigs per hectare, breeding for 120 days, harvesting 6798.3 kilograms of prawns, producing 11970 shrimps per hectare. Kilograms, the total output value of 21,8870.5 yuan, after deduction of costs, net profit of 10,3495.4 yuan, more significant benefits. At that time, this model did not attract people's attention. The main reasons were the low price of shrimp, the high cost of shrimp ponds, the hard bottom of the pond, and the use of stone and cement around the slope to protect the slopes. The people were afraid of high costs and were difficult to recycle. In 1994, Nanmengou Co., Ltd. of Xiyang Township, Xuwen County used the technical strength of the Zhanjiang Fisheries Academy to build a 13-hectare shrimp pond. Due to high aquaculture production and good efficiency, the Zhanjiang municipal government held a live meeting at Xuwen to promote this. In 1995, another 4 hectares was expanded on this field.
In 1994 and 1995, the site had invested RMB 2 million in infrastructure equipment and 6.13 hectares of built pool. The power supply, aeration, and water supply equipment were fully equipped. Since the impact of building a pond in 1994 only raised one crop, in 1996, due to the typhoon No. 15 attack, it was late to make a loss, and it was also raised one crop. If it is normal to raise two crops in 1995, the annual net profit is 98.96 million yuan, and it can be recovered in two years. All investment. Under the impetus of this field, shrimp cultivation in high-level ponds in our city developed rapidly. By the end of last year, 2350 hectares of shrimp ponds had been developed, of which 530 hectares were higher. High-end shrimp ponds are generally built on high tides in the coastal zone and are raised by lifting water, increasing oxygen, and semi-closed cultivation. Higher standards of shrimp ponds, 4-50 thousand mu seedlings, lower standards of the pool, put l--2 million seedlings, breeding for 120 days can be harvested. Its advantages: high yield per unit area, good efficiency, ability to resist sea tide, large safety factor, convenient dredging and sewage discharge, favorable to disinfection of ponds and prevention of diseases, etc., is suitable for the development of shrimp farming in the city from extensive to intensive development Way.
2, multi-level high pool breeding
This model was invested by 260,000 yuan at Daxing Nursery Yard in Dongli Town, Leizhou City at the end of 1997. It used a land-level difference to build a group of three-level high-grade shrimp ponds with a total area of ​​13 acres, of which the first-class pool was 2 acres and the second-level pool was 2 acres. Tertiary pool 10 acres. The first and second grade pools are hard bottoms, sloped concrete walls, third grade pool bottom sands, and pool wall concrete slopes. The bottom slope is greater than 1%, the first and second pools are 1.5 meters apart, and the second and third pools are 1.8 meters apart. They are connected by pipelines and are equipped with aerators, pumps, and other equipment to form a three-level intensive shrimp production line. On February 21, 1998, the first seedling was launched, and shrimps were cultured. In mid-November, 4 larvae were harvested. Each quail culture lasted for about 100 days. Each pond breeding time was 30-38 days. Shrimp size 70--76 Tail / kg, a total yield of 13,800 kilograms, output value of 620,000 yuan, gross profit 342,000 yuan, the fifth batch of Japanese shrimp, the harvest after the 1999 Spring Festival, is expected to harvest more than 2,500 kilograms. The success of this three-level shrimp pool intensive culture is another breakthrough for the healthy breeding of shrimp in our city. Its main advantages are: it greatly reduces the pollution at the bottom of the pool, facilitates dredging and disinfection, and effectively prevents the occurrence of shrimp diseases. At the same time, more high-density culture can be used to achieve a significant increase in yield and increase efficiency.
3, closed, low salinity, low density farming
This model has emerged in recent years. The use of old shrimp ponds in Leizhou, Suixi, and Potou is relatively effective.
“Closed†is a traditional method of changing the large-scale irrigation in the past. After disinfecting the seedlings before clearing, the seawater is disinfected once in a single step, and then the algae is released according to conventional methods. The whole breeding process is no longer used to enter seawater. This cuts off the pathway for pathogens to enter the shrimp ponds with the seawater. In order to maintain the first pool of water, apply photosynthetic bacteria once a month at a rate of 5-7 kg per acre, and according to changes in water quality, apply zeolite powder or other drugs several times during the growth period of the shrimp. Pay attention to maintaining the pH value. Between 8.0-8.6, its role is to decompose the sulfides, ammonia nitrogen and other harmful substances in the pool in order to improve water quality and inhibit the growth of bacteria. "Low salinity" means that the seedlings begin to make up fresh water within half a month, with a supplement of 5 to 10 centimeters at a time, and the salinity changes do not exceed 2 at a time until they fall to about 5 torr before harvesting. Adding freshwater can not only stimulate the growth of shrimp, but also inhibit the vibrio in shrimp ponds, reproduction and spread of the virus to reduce the outbreak of shrimp disease. "Low density" means that the old shrimp pond should not be overcast and the harvested yield should not be too high. General business investment seedlings in the 3000 - 10000 or so, depending on the condition of shrimp ponds. For example, in 1998, 800 acres of old shrimp pond in Dongli Town, Leizhou City, with serious siltation, no sewage treatment, poor drainage and drainage conditions, after transformation, 3000 seedlings per mu, breeding period 163 days, shrimp production 46626 kg, shrimp specifications 20 -24/kg, profit of 400,000 yuan. Another example is the 347-mu old shrimp pond in Jiexi Town, Suixi County. After dredging and sand-filling, a few freshwater wells are supported and about 10,000 mu of seedlings are planted. Since 1994, it has been highly productive and efficient for five consecutive years. More than one million yuan, the best level is in 1996, two breeding, production 70,000 kilograms, the output value of 4 million yuan, 1.8 million yuan net profit.
4, "shrimp fish", "shrimp algae" polyculture, rotation
In recent years, the shrimp ponds in Leizhou, Xuwen, Potou, Lianjiang, and the East China Sea have adopted this model more generally, and the effect is relatively good. In 1997, 500 acres of old shrimp ponds in Qianyuan Park, Leizhou City were mixed with polyploid prawn and tilapia. After one month of shrimp seedlings, tilapia fry (15 cm in length and 6 cm in length) was distributed with 15-20 tails/mu. , Culture rebate days, to be successful, collecting 25,000 kilograms of shrimp, tilapia 5000 kilograms, the output value of more than 250 million, net profit of 1.5 million. The average production value and profit per mu are 5,000 yuan and 3,000 yuan respectively, which is even higher than some newly developed shrimp ponds. In this model, tilapia mostly live in the bottom of shrimp ponds and feed on shrimps and excreta. They play the role of the bottom scavenger. At the same time, the fish and shrimps chase each other, which in turn stimulates the circulation of the pool water to achieve oxygenation. . In 1998, the field was reconstructed and deepened to 3- or 4-meters. The large yellow croaker was rotated and 500 mu were planted (4.7 cm in length). By the beginning of March this year, it had been raised for 13 months and had an average weight of 400 g. It is currently growing well. The water harvest began in June this year. 50 acres of old shrimp ponds in Liusha Town, Leizhou City. From 1996 to 1998, they insisted on the polyculture of shrimps and river fences. Each period of shrimp farming cycle is 160--180 days. The shrimp specifications are 12--20 tails/kg, for three consecutive years. Disease-free, the effect is better. The cumulative harvest of shrimp for three years was 8900 kilograms, with an output value of more than 900,000 yuan and net profit of more than 500,000 yuan. This model adopts photosynthetic bacteria and Jiang Lei to carry out photosynthesis at the bottom of the pool and plays the role of “ecological disease prevention and shrimp farming†to prevent the outbreak of shrimp disease and achieve success. In addition, the Longyingwei Shrimp Farm in Lianjiang City uses part of shrimp ponds for the rearing of giant prawn and Macrobrachium rosenbergii. The benefits are also good, and they should be worthy of learning and spreading.
Third, questions and suggestions
Zhanjiang has developed a variety of models for shrimp aquaculture. Some suggestions and suggestions have been put forward on how to select and improve various breeding models.
1, on the issue of high shrimp pond site selection
High-grade shrimp ponds, especially high-standard shrimp ponds, have large investments and high costs. In order to obtain the desired results, comprehensive consideration must be given when selecting sites. The first is the sediment quality. Generally, the medium-coarse sand is better. In addition to thorough drying and easy dredging, the sandy land can also reduce the reproduction of small shellfish, crabs, and copepods, thereby reducing the spread of the virus and preventing the outbreak of shrimp disease. The second is to choose within the protective forest belt, which will help the typhoon season reduce the stress status of shrimp and prevent the diseases caused by typhoon. Third, avoid choosing polluted places in the sea area, otherwise it will increase the difficulty of water treatment. Judging from the current situation in the sea area, the high-level ponds should be filtered or precipitated in order to achieve the purpose of healthy breeding.
2. About multi-level high shrimp pond construction and breeding management issues
This mode of aquaculture production time is not long, lack of experience, there are several issues must be further explored: First, the number of three-level pool difference is the best, the design principle of the gap, not only to ensure the safety of the shrimp when the water quality of the pool needs , but also consider not to increase the pool cost due to a large gap. When choosing a multi-level high-level pool, it is necessary to adjust measures to local conditions and give priority to terrain advantages that have a positional difference so as to reduce the cost. The second is the third-level pond as a group, from high to low, grading culture, how much the best ponds at all levels, from the current high-level pool breeding experience, see 40,000-50,000 per mu seedlings, about 10 acres Quartet or round pool is easy to manage, with high yield and good efficiency. Therefore, the third level (ie, commercial shrimp) pool of multi-level high-level pools is designed to be about 10 mu, so how big the first and second pools should be, and it needs further modelling, the size of the ponds at various levels and the number of seedlings, and the breeding time. , survival rate, convenient management and other factors. The proportion of tertiary pool in Daxing Nursery Farm, Dongli Town, Leizhou City is 1:2.5:10. Judging from the farm farming situation, the first-level pool should be slightly better, which will increase the survival rate and growth rate. The third is the third-level pond breeding, which will greatly reduce the silt pollution in the bottom of the pool, reduce the chance of pathogens breeding and growth, and effectively prevent the occurrence of shrimp disease, especially one. The secondary pool, the pool wall and the bottom of the pool are all cemented. After the shrimps are moved to the pool, they can be thoroughly cleaned and disinfected. There is no problem of accumulation of dirt, thus ensuring the success of each shrimp culture. However, how long it takes for each pond to grow is appropriate, and it needs further exploration. The cultivation time of the first, second, and third-level tanks in the Daxing nursery is 3O--32, 31--34, and 35--38 days. It seems that the specifications of the shrimp are relatively small, with 70 tails per kilogram. If the time of each pond is adjusted to 30, 40, or 50 days, it will be better and the specifications will be reached after 120 days of breeding.
3, on the old shrimp pond transformation and breeding mode choice
The transformation of old shrimp ponds in our city is based on the combination of local conditions, classification and management, transformation and reform of the breeding mode. For shallow water tanks to deepen, supporting aerator, generally can be successful. For shrimp and ponds where irrigation and irrigation are not separated and the floodgates are few, the shrimp ponds must be treated in stages. For shrimp ponds that have accumulated deep and long-term water level, they must not be “single-driedâ€. It is only necessary to conduct joint dry-drawing treatment. It is advisable to place sand and freshwater channels for the closed or semi-closed culture in places where conditions permit.
4, on the "shrimp algae" polyculture problem
The polyculture of prawns and river fences can achieve certain results in transforming the shrimp pond environment and preventing the occurrence of shrimp disease. However, to significantly increase shrimp production, shrimp ponds with deep water levels must be required. This is in contradiction with the growth and breeding of river barriers. One of the reasons why this cannot be achieved is because of this. It is recommended to adopt "sub-station" farming, first to raise a special pond to raise rivers and raise water, and then to provide algae-filtered water to the shrimp ponds. This will help cut off pathogens and increase shrimp production.
The city's shrimp farming began in 1974 when it took in the sea area Moji and Longhair prawn seedlings. In 1980, for the first time, 2.08 million mimics and long-haired prawn seedlings were artificially cultivated. In the same year, 7.27 hectares were bred. The average hectare yielded 1,260 kg of shrimp, which made the city's shrimp breeding start.
In 1984, the first introduction of P. ostracodus was conducted in Lianjiang City. The area of ​​cultivation was 0.4 hectares. The average hectare produced 997.5 kilograms of shrimp, and the net profit was 1,060 yuan. This provided the basis for the municipal Party committee to vigorously develop the shrimp industry. Therefore, from 1985 to 1988, there was a “shrimp fever†for the first time, and five acres of contiguous shrimp ponds were constructed, mainly in Leizhou, Lianjiang and Potou. In 1988, the shrimp culture area was 8186.7 hectares and the yield was 3,762 tons, which was 17.95 times and 14.87 times higher than that in 1985 respectively.
In 1989 and 1990, the enthusiasm of the masses of shrimp farming was high, and the farming techniques were gradually improved. The ecological conditions in the shrimp ponds were still relatively good. They should have achieved high yields and high efficiency. However, due to political factors and the country’s monetary tightening at the time, there were “dead shrimps†and “ Starved shrimp, thus making the shrimp industry into the first trough, in 1990 shrimp area fell to 3,064 hectares of shrimp production 2,733 tons.
From 1991 to 1992, with the improvement of social and economic conditions, shrimp production began to pick up for the first time. From 1991, Penaeus ostracodus became the main breed of shrimp farming. In that year, 727.22 million pairs of shrimp seedlings were produced artificially, accounting for the shrimp of the current year. The total number of seedlings is 66.5%, aquaculture area is 5915 hectares, 9,824 tons of shrimp are produced, and 1660.86 kilograms of shrimp are produced per hectare, creating the highest level of historical yield. However, by the second half of 1992, an outbreak of shrimp disease began.
From 1993 to 1994, due to the full spread of shrimp disease, the shrimp industry saw a second trough. In 1994, the shrimp area was 7,671 hectares, producing 5,306 tons of shrimp and producing 69.7 kg of shrimp per hectare.
From 1995 to 1998, there was a second "shrimp fever". In 1996, the area of ​​shrimp farming was 10042 hectares, with a production of 10,194 tons, and 1015 kilograms of shrimp per hectare, breaking the 10,000-ton mark for the first time. In 1997, the area of ​​shrimp farming was 10,666 hectares, with a production of 14,400 tons and 1,350 kg of shrimp per hectare. In 1998, the area of ​​shrimp farming was 13,800 hectares, with a production of 21,200 tons and 1,536 kilograms of shrimp per hectare. For three consecutive years, it has achieved the best level of history. The characteristics of shrimp aquaculture at this stage: First, the interests of the socialist market economy are driven. Although the risk of shrimp farming is large, the breeding cycle is short and can be raised for a few times a year. This is more effective and the enthusiasm of the masses is high. Therefore, the main investors have turned from the past government to production operators, forming a multi-subject main investment pattern. According to the survey, in 1997 and 1998, the city invested nearly 300 million yuan in shrimp raising, of which 95% were self-funded by owners, and an area of ​​more than 50,000 mu was expanded. Second, with the improvement of aquaculture technology, the aquaculture production mode has changed from extensive to intensive. The vast number of aquatic technology cadres and shrimp farmers insisted on exploration, created a semi-closed or closed shrimp farming technology, isolated pathogenic technology with fresh water, high-pot shrimp farming technology, and so on, so that a new way for the shrimp aquaculture industry. Third, the infrastructure for shrimp farming has been strengthened. The city has more than 100 shrimp seedlings and nursery sites with more than 100,000 cubic meters of water. It has two national feed factories (Guangdong, etc.) and an annual production capacity of 30,000 tons. There are also complete processing refrigeration plants and pharmaceuticals. These provide the basic conditions for the development of shrimp farming. The fourth is to increase the socialization of shrimp farming services. In recent years, feed mills have taken the lead and hired shrimp specialists as consultants to form feed, seedlings, drugs, and technology train services to shrimp ponds. They have played a significant role in solving the problems in the production of shrimps and shrimps. Farmers welcome.
The main problems in current shrimp farming: First, shrimp disease still plagues the development of shrimp farming. In recent years, the annual incidence rate is 20-30%, the disease is fierce, and the cause is complex. Most of them are mainly viruses, and the viruses and bacteria are complicated. The medication is invalid. Second, the transformation of aging shrimp ponds is difficult. There are 100,000 mu of aging shrimp ponds in the city. The conditions are poor and the yield is low. Although some of the shrimp ponds were reconstructed and the farming model was reformed, there are still some shrimp ponds that have not escaped the predicament. Third, some newly developed shrimp ponds have a low standard and it is difficult to increase production. Fourth, some shrimp farmers have not kept up with the prevention and control of shrimp disease and their aquaculture management. The training needs to be further strengthened. All these problems must be taken seriously and resolved step by step.
Second, several kinds of shrimp breeding mode
1, high pool breeding
This model was first established in 1991 by the Zhanjiang Fisheries Bureau using open air 0.57 hectares of land in a direct-owned Hongkong shrimp hatchery, releasing 750,000 pigs per hectare, breeding for 120 days, harvesting 6798.3 kilograms of prawns, producing 11970 shrimps per hectare. Kilograms, the total output value of 21,8870.5 yuan, after deduction of costs, net profit of 10,3495.4 yuan, more significant benefits. At that time, this model did not attract people's attention. The main reasons were the low price of shrimp, the high cost of shrimp ponds, the hard bottom of the pond, and the use of stone and cement around the slope to protect the slopes. The people were afraid of high costs and were difficult to recycle. In 1994, Nanmengou Co., Ltd. of Xiyang Township, Xuwen County used the technical strength of the Zhanjiang Fisheries Academy to build a 13-hectare shrimp pond. Due to high aquaculture production and good efficiency, the Zhanjiang municipal government held a live meeting at Xuwen to promote this. In 1995, another 4 hectares was expanded on this field.
In 1994 and 1995, the site had invested RMB 2 million in infrastructure equipment and 6.13 hectares of built pool. The power supply, aeration, and water supply equipment were fully equipped. Since the impact of building a pond in 1994 only raised one crop, in 1996, due to the typhoon No. 15 attack, it was late to make a loss, and it was also raised one crop. If it is normal to raise two crops in 1995, the annual net profit is 98.96 million yuan, and it can be recovered in two years. All investment. Under the impetus of this field, shrimp cultivation in high-level ponds in our city developed rapidly. By the end of last year, 2350 hectares of shrimp ponds had been developed, of which 530 hectares were higher. High-end shrimp ponds are generally built on high tides in the coastal zone and are raised by lifting water, increasing oxygen, and semi-closed cultivation. Higher standards of shrimp ponds, 4-50 thousand mu seedlings, lower standards of the pool, put l--2 million seedlings, breeding for 120 days can be harvested. Its advantages: high yield per unit area, good efficiency, ability to resist sea tide, large safety factor, convenient dredging and sewage discharge, favorable to disinfection of ponds and prevention of diseases, etc., is suitable for the development of shrimp farming in the city from extensive to intensive development Way.
2, multi-level high pool breeding
This model was invested by 260,000 yuan at Daxing Nursery Yard in Dongli Town, Leizhou City at the end of 1997. It used a land-level difference to build a group of three-level high-grade shrimp ponds with a total area of ​​13 acres, of which the first-class pool was 2 acres and the second-level pool was 2 acres. Tertiary pool 10 acres. The first and second grade pools are hard bottoms, sloped concrete walls, third grade pool bottom sands, and pool wall concrete slopes. The bottom slope is greater than 1%, the first and second pools are 1.5 meters apart, and the second and third pools are 1.8 meters apart. They are connected by pipelines and are equipped with aerators, pumps, and other equipment to form a three-level intensive shrimp production line. On February 21, 1998, the first seedling was launched, and shrimps were cultured. In mid-November, 4 larvae were harvested. Each quail culture lasted for about 100 days. Each pond breeding time was 30-38 days. Shrimp size 70--76 Tail / kg, a total yield of 13,800 kilograms, output value of 620,000 yuan, gross profit 342,000 yuan, the fifth batch of Japanese shrimp, the harvest after the 1999 Spring Festival, is expected to harvest more than 2,500 kilograms. The success of this three-level shrimp pool intensive culture is another breakthrough for the healthy breeding of shrimp in our city. Its main advantages are: it greatly reduces the pollution at the bottom of the pool, facilitates dredging and disinfection, and effectively prevents the occurrence of shrimp diseases. At the same time, more high-density culture can be used to achieve a significant increase in yield and increase efficiency.
3, closed, low salinity, low density farming
This model has emerged in recent years. The use of old shrimp ponds in Leizhou, Suixi, and Potou is relatively effective.
“Closed†is a traditional method of changing the large-scale irrigation in the past. After disinfecting the seedlings before clearing, the seawater is disinfected once in a single step, and then the algae is released according to conventional methods. The whole breeding process is no longer used to enter seawater. This cuts off the pathway for pathogens to enter the shrimp ponds with the seawater. In order to maintain the first pool of water, apply photosynthetic bacteria once a month at a rate of 5-7 kg per acre, and according to changes in water quality, apply zeolite powder or other drugs several times during the growth period of the shrimp. Pay attention to maintaining the pH value. Between 8.0-8.6, its role is to decompose the sulfides, ammonia nitrogen and other harmful substances in the pool in order to improve water quality and inhibit the growth of bacteria. "Low salinity" means that the seedlings begin to make up fresh water within half a month, with a supplement of 5 to 10 centimeters at a time, and the salinity changes do not exceed 2 at a time until they fall to about 5 torr before harvesting. Adding freshwater can not only stimulate the growth of shrimp, but also inhibit the vibrio in shrimp ponds, reproduction and spread of the virus to reduce the outbreak of shrimp disease. "Low density" means that the old shrimp pond should not be overcast and the harvested yield should not be too high. General business investment seedlings in the 3000 - 10000 or so, depending on the condition of shrimp ponds. For example, in 1998, 800 acres of old shrimp pond in Dongli Town, Leizhou City, with serious siltation, no sewage treatment, poor drainage and drainage conditions, after transformation, 3000 seedlings per mu, breeding period 163 days, shrimp production 46626 kg, shrimp specifications 20 -24/kg, profit of 400,000 yuan. Another example is the 347-mu old shrimp pond in Jiexi Town, Suixi County. After dredging and sand-filling, a few freshwater wells are supported and about 10,000 mu of seedlings are planted. Since 1994, it has been highly productive and efficient for five consecutive years. More than one million yuan, the best level is in 1996, two breeding, production 70,000 kilograms, the output value of 4 million yuan, 1.8 million yuan net profit.
4, "shrimp fish", "shrimp algae" polyculture, rotation
In recent years, the shrimp ponds in Leizhou, Xuwen, Potou, Lianjiang, and the East China Sea have adopted this model more generally, and the effect is relatively good. In 1997, 500 acres of old shrimp ponds in Qianyuan Park, Leizhou City were mixed with polyploid prawn and tilapia. After one month of shrimp seedlings, tilapia fry (15 cm in length and 6 cm in length) was distributed with 15-20 tails/mu. , Culture rebate days, to be successful, collecting 25,000 kilograms of shrimp, tilapia 5000 kilograms, the output value of more than 250 million, net profit of 1.5 million. The average production value and profit per mu are 5,000 yuan and 3,000 yuan respectively, which is even higher than some newly developed shrimp ponds. In this model, tilapia mostly live in the bottom of shrimp ponds and feed on shrimps and excreta. They play the role of the bottom scavenger. At the same time, the fish and shrimps chase each other, which in turn stimulates the circulation of the pool water to achieve oxygenation. . In 1998, the field was reconstructed and deepened to 3- or 4-meters. The large yellow croaker was rotated and 500 mu were planted (4.7 cm in length). By the beginning of March this year, it had been raised for 13 months and had an average weight of 400 g. It is currently growing well. The water harvest began in June this year. 50 acres of old shrimp ponds in Liusha Town, Leizhou City. From 1996 to 1998, they insisted on the polyculture of shrimps and river fences. Each period of shrimp farming cycle is 160--180 days. The shrimp specifications are 12--20 tails/kg, for three consecutive years. Disease-free, the effect is better. The cumulative harvest of shrimp for three years was 8900 kilograms, with an output value of more than 900,000 yuan and net profit of more than 500,000 yuan. This model adopts photosynthetic bacteria and Jiang Lei to carry out photosynthesis at the bottom of the pool and plays the role of “ecological disease prevention and shrimp farming†to prevent the outbreak of shrimp disease and achieve success. In addition, the Longyingwei Shrimp Farm in Lianjiang City uses part of shrimp ponds for the rearing of giant prawn and Macrobrachium rosenbergii. The benefits are also good, and they should be worthy of learning and spreading.
Third, questions and suggestions
Zhanjiang has developed a variety of models for shrimp aquaculture. Some suggestions and suggestions have been put forward on how to select and improve various breeding models.
1, on the issue of high shrimp pond site selection
High-grade shrimp ponds, especially high-standard shrimp ponds, have large investments and high costs. In order to obtain the desired results, comprehensive consideration must be given when selecting sites. The first is the sediment quality. Generally, the medium-coarse sand is better. In addition to thorough drying and easy dredging, the sandy land can also reduce the reproduction of small shellfish, crabs, and copepods, thereby reducing the spread of the virus and preventing the outbreak of shrimp disease. The second is to choose within the protective forest belt, which will help the typhoon season reduce the stress status of shrimp and prevent the diseases caused by typhoon. Third, avoid choosing polluted places in the sea area, otherwise it will increase the difficulty of water treatment. Judging from the current situation in the sea area, the high-level ponds should be filtered or precipitated in order to achieve the purpose of healthy breeding.
2. About multi-level high shrimp pond construction and breeding management issues
This mode of aquaculture production time is not long, lack of experience, there are several issues must be further explored: First, the number of three-level pool difference is the best, the design principle of the gap, not only to ensure the safety of the shrimp when the water quality of the pool needs , but also consider not to increase the pool cost due to a large gap. When choosing a multi-level high-level pool, it is necessary to adjust measures to local conditions and give priority to terrain advantages that have a positional difference so as to reduce the cost. The second is the third-level pond as a group, from high to low, grading culture, how much the best ponds at all levels, from the current high-level pool breeding experience, see 40,000-50,000 per mu seedlings, about 10 acres Quartet or round pool is easy to manage, with high yield and good efficiency. Therefore, the third level (ie, commercial shrimp) pool of multi-level high-level pools is designed to be about 10 mu, so how big the first and second pools should be, and it needs further modelling, the size of the ponds at various levels and the number of seedlings, and the breeding time. , survival rate, convenient management and other factors. The proportion of tertiary pool in Daxing Nursery Farm, Dongli Town, Leizhou City is 1:2.5:10. Judging from the farm farming situation, the first-level pool should be slightly better, which will increase the survival rate and growth rate. The third is the third-level pond breeding, which will greatly reduce the silt pollution in the bottom of the pool, reduce the chance of pathogens breeding and growth, and effectively prevent the occurrence of shrimp disease, especially one. The secondary pool, the pool wall and the bottom of the pool are all cemented. After the shrimps are moved to the pool, they can be thoroughly cleaned and disinfected. There is no problem of accumulation of dirt, thus ensuring the success of each shrimp culture. However, how long it takes for each pond to grow is appropriate, and it needs further exploration. The cultivation time of the first, second, and third-level tanks in the Daxing nursery is 3O--32, 31--34, and 35--38 days. It seems that the specifications of the shrimp are relatively small, with 70 tails per kilogram. If the time of each pond is adjusted to 30, 40, or 50 days, it will be better and the specifications will be reached after 120 days of breeding.
3, on the old shrimp pond transformation and breeding mode choice
The transformation of old shrimp ponds in our city is based on the combination of local conditions, classification and management, transformation and reform of the breeding mode. For shallow water tanks to deepen, supporting aerator, generally can be successful. For shrimp and ponds where irrigation and irrigation are not separated and the floodgates are few, the shrimp ponds must be treated in stages. For shrimp ponds that have accumulated deep and long-term water level, they must not be “single-driedâ€. It is only necessary to conduct joint dry-drawing treatment. It is advisable to place sand and freshwater channels for the closed or semi-closed culture in places where conditions permit.
4, on the "shrimp algae" polyculture problem
The polyculture of prawns and river fences can achieve certain results in transforming the shrimp pond environment and preventing the occurrence of shrimp disease. However, to significantly increase shrimp production, shrimp ponds with deep water levels must be required. This is in contradiction with the growth and breeding of river barriers. One of the reasons why this cannot be achieved is because of this. It is recommended to adopt "sub-station" farming, first to raise a special pond to raise rivers and raise water, and then to provide algae-filtered water to the shrimp ponds. This will help cut off pathogens and increase shrimp production.
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