Large-scale cultivation of pike crab in marine ponds - a key technology for efficient cultivation of Japanese shrimp
In recent years, large-scale application of anti-residue devices in the breeding of "Pike Crab- Japanese Shrimp" has emerged in seawater ponds such as Dengbu Island in Zhoushan, Zhejiang, and Lotus in Xiangshan, Ningbo, which has achieved high yield and high efficiency of crab shrimp. From 2017 to 2018, a farmer in Xiangshan Lotus Pond showed that the yield of pike crab exceeded 50 kg, the yield of Japanese shrimp exceeded 30 kg, the single output value reached more than 20,000 yuan, and the profit per mu reached more than 10,000 yuan.
The habit of cannibalism of pike crabs is one of the main reasons for the low survival rate, and its aquaculture survival rate has been below 5%, or even below 3%, and such a low survival rate is a great waste of pond resources. Seawater ponds such as Dengbu Island in Zhoushan, Zhejiang and Lotus in Xiangshan, Ningbo have applied anti-residue devices on a large scale in aquaculture, achieving high yield and high efficiency of crab shrimp.
1. Materials and methods
(1) Ponds
The test materials are transported by low temperature to the test pond located in the lotus farm in Xizhou Town, Xiangshan County, on the verge of the port of Xiangshan Port, with a total area of 66.67hm 2. The bottom of the pond is silt and sandy, and there are double gates, and the inlet and drainage systems are separated, and the water can enter for more than 10 days per tide. Equipped with bottom aeration 2.25kw/hm2. Among them, the test pond in 2017 was 1.6hm 2, and the test pond in 2018 was 1.86hm 2.
(2) Residual equipment
1. Anti-residue device material: can be customized to make a plastic frame, you can also use discarded fruit basket. Plastic basket anti-residue device, long × high× width of 36cm× 17cm×23cm, four corners of the matching pointed foot inserted into the beach surface 4cm, when used from the middle saw off, forming 2 independent anti-residue basket; fruit basket anti-disability device, when used from the middle saw off, the formation of 2 independent anti-residue basket.
2. Anti-residue basket placement method: the spacing of the oxygenation pipe at the bottom of the pond is 12m, and the spacing of the hole is 3.0m. The anti-residue basket is mainly laid on the beach surface, along both sides of the bottom oxygenation pipe, and the spacing of the anti-residue basket is 1.8m/only. The anti-residue basket is placed before the pike crab is self-breeding, and if the factory crab seedlings are released, the anti-residue basket can be postponed after the crab seedlings are stocked. According to the actual level of breeding technology, the number of anti-residue baskets can be appropriately increased or decreased.
(3) Clear the pond
Before and after the Spring Festival, the shuttle crabs are caught and the dry pond is dried. In late March, the spray method was used to kill the moss with drugs in the whole pond, requiring no dead ends. Clear the pond 2d with bleach powder 900kg/hm2 with water 2d before stocking crab seedlings.
(4) Stocking of seedlings
1. Pike crab seedlings are self-propagating
On May 12, the East China Sea wild three-wart pike crab with complete appendages, full eggs and black (gray) seeds was purchased from Shipu Port, hung in a pond (1 seed crab/basket) in a plastic basket, and fed 2 to 3 grains of clams per crab per day, a total of 128 seed crabs were stocked, with a size of 0.25 kg/piece, the survival rate of seed crabs was 75%, and the stocking density of seed crabs was 68.8/hm 2. The release of the crabs began on May 15 and was completed on May 20. Pike crab seedlings from the breeding of juvenile crabs for the shortest time of 14 days, generally 15d to 16d to see stage I juvenile crabs. Z2 to z3 were seen on May 21, big-eyed juveniles were seen on May 23, stage I juvenile crabs were seen on May 27, and stage iii to v juvenile crabs were sold on June 8. The self-propagation process of pike crabs opens the bottom-filler aerator all day long.
z1~z2 stage: feeding soybean milk, spirulina powder and shrimp slices. In the morning, soybean syrup was sprinkled with 8kg/hm2 and spirulina powder was fed 0.15kg/hm2. In the afternoon, spirulina powder and shrimp slices are fed 0.15 kg/hm2 each. After z2, add 1.0kg/hm 2 shrimp slices in the afternoon. Harvest insect feeding 0.2kg/hm 2, harvest insects using red barrel hatching, with 250w incandescent lamp as a heat source, incubation 48h after the whole pool spilled, harvest insect hatching water temperature requirements control at 28 °C, water temperature should not exceed 30 °C.
z3~z4 stage: feeding soybean milk, shrimp chips, frozen copepods, duck eggs, etc. In the morning, 8 kg/hm 2 soybeans and 1.5 kg/hm 2 of duck eggs are steamed and crushed with residue. In the afternoon, shrimp flakes 1.0 kg/hm 2, Harvest Worm 0.2 kg/hm 2, frozen copepods 4 kg/hm 2.
m stage: Feeding frozen copepods, duck eggs, fish pulp, harvest worms and frozen trash fish. Pitch once in the morning and once in the evening, with a feeding ratio of 4:6. In the morning, fish slurry is fed 5.0kg/hm 2, duck eggs 1.5kg/hm 2, frozen copepods 4.0kg/hm 2, and in the evening, harvest worms are fed 0.3kg/hm 2, frozen copepods 7.5kg/hm 2, and frozen trash fish 10kg/hm 2.
Stage c: Starting from c1 to feed frozen trash fish, the amount of feeding gradually increases from 10kg/hm 2 to 15kg/hm2 in c1, and gradually feeds frozen trash fish and compound feed after c5. Pike crab seedlings start from c3, depending on the number of seedlings in the pond, take seven or eight o'clock at night to trap crab seedlings for sale.
2. Stocking of Japanese shrimp seeds
On 5 July, Nicholas nicholas was purchased from local nurseries, with a total of 280,000 seedlings and a seedling density of 150,000/hm2. The stocking density of Japanese shrimp depends on the water exchange conditions of ponds and the level of breeding technology, and the stocking density of Japanese shrimp in Xiangshan is generally 0.75 million /hm 2 to 150,000 fish /hm 2 (seedlings are released from the end of June to early July), while the stocking density of Zhoushan Dengbu Island is generally 450,000 fish/hm 2 to 600,000 fish/hm 2.
(5) Cultivation management
1. Water quality management and disease prevention
Mainly to regulate water quality, the late stage of seedlings began to use em bacteria to regulate water quality, pike crab v stage - vi stage, the use of compound iodine disinfection water body, and with "fibrous net" to kill ciliate once. After that, the water body is disinfected with compound iodine or quicklime every month, and the glucose ion calcium and the substrate modifier are sprinkled once a month, and the em bacteria are sprinkled once every half month. Regularly test water quality indicators and record, early detection of problems and timely treatment, so that the aerator is opened frequently and the aerator is opened in a timely manner.
2. Feed feeding
Feeding is given twice in the morning and evening, compound feed in the morning and frozen (fresh) trash fish in the evening. It is necessary to pay attention to the growth of shrimp and crabs and the biological situation of pond bait, and adjust the amount of bait in a timely manner during typhoons, heavy rainfall, molting, etc. In view of the biological habits of pike crab and Japanese shrimp, low-value shellfish such as "compound feed + frozen small trash fish + sea melon seeds (rainbow cherry clams) are used". Sea melon seeds start from late July and are fed until the beginning of October, feeding continuously for 5d to 7d every half month, and proper nutritional fortification is conducive to shrimp and crab molting.
3. Male breeding
From the end of July, male crabs are caught by releasing gillnets or fishing. On the one hand, it can supplement the listing of fresh aquatic products during the rest period and increase a part of the economic income, on the other hand, control the ratio of male and female crabs in the pond (6:1 is appropriate), and achieve high yield of female crab cream crabs (egg-hugging crabs).
4. Cultivate catching
Japanese shrimp are round-caught. The price of Japanese shrimp is higher around the National Day, and cage fishing can be used to gradually catch and market until around New Year's Day. The catch of pike crabs has the highest price around the Spring Festival, and it is important not to extend the catch to March to increase the risk of market sales.
Second, the results of breeding
In 2017, the total output value was 484,900 yuan, of which the unit output of pike crab was 772.5kg/hm 2, with an output value of 265,500 yuan; the unit output of Japanese shrimp was 455.63kg/hm2, with an output value of 149,400 yuan; and the output value of clams was 70,000 yuan. The cost is 236,800 yuan, the pond rent fee is 76,800 yuan, the seedling fee is 30,000 yuan, the feed fee is 80,000 yuan, the electricity and drug cost is 10,000 yuan, and the labor cost is 40,000 yuan. The actual profit was 248,100 yuan, and the unit profit reached 155,100 yuan/hm2.
In 2018, the total output value was 651,300 yuan, of which the unit output of pike crab was 1103.23kg/hm 2, with an output value of 400,000 yuan; the unit output of Japanese white shrimp was 470.43kg/hm 2, with an output value of 201,300 yuan; and the sales fee of pike crab seeds was 50,000 yuan. The cost is 267,000 yuan, the pond rent fee is 109,000 yuan, the Japanese shrimp seed fee is 0.3 million yuan, the crab seed fee is 20,000 yuan, the feed fee is 85,000 yuan, the electricity and medicine fee is 10,000 yuan, and the labor fee is 40,000 yuan. The actual profit was 384,300 yuan, and the unit profit reached 206,600 yuan/hm2.
3. Discussion
(1) On the large-scale application of anti-disability devices
Discussion on improving the survival rate of shrimp and crab farming, the survival rate of pike crab farming has been below 5%, or even below 3%, and such a low survival rate of aquaculture is a great waste of pond resources. The cannibalism habit of pike crabs has long been one of the main reasons for the low survival rate. Although the main pike crab producing areas have carried out experiments on the installation of hidden material devices such as moso bamboo, tiles and mesh on the beach surface, no systematic studies have been carried out. In recent years, scientific research units such as Zhejiang Marine fisheries research institute have carried out systematic research on the prevention of crab residues in Zhoushan, Xiangshan and other places, and have achieved large-scale promotion. In 2017, the anti-disability test of pike crab was carried out in the 2 ponds of Xiangshan Lotus Pond, and the unit yield of pike crab was more than 40 kg, and the unit yield of Japanese shrimp was more than 25 kg. In 2018, the farm tested 6 ponds, and the unit yield of barracuda crab was more than 50 kg to 70 kg, and the unit yield of Japanese shrimp was more than 30 kg. In 2019, the farm applied 20 ponds with pike crab anti-disability devices, and the promotion area in Huangsuiao, Gaotang Island, Sizhou first place reached more than 100hm2. Through the two-year multilateral test side promotion, the anti-residue effect of pike crab anti-residue basket is good, the technical route is feasible, and the application of large-scale anti-residue device in pike crab breeding pond has become one of the key technical measures to improve the survival rate of shrimp and crab farming. The next step is to strengthen research on the placement density, angle, moss anti-clogging and rational structural layout with the pond.
Harvest of crabs
(2) Several key technical measures to improve the survival rate of shrimp and crab farming
1. Strictly control the clearance of ponds. So far, most of the breeding ponds have adopted crab shrimp and shellfish polyculture, and the ponds are not dried all year round, and a few farmers use pesticides to clear the ponds. Therefore, the deterioration of the bottom of the pond, the proliferation of bacteria at the bottom of the pond, the pesticide residue, the impact on the juvenile shrimp and crab is very large, and the traditional breeding concept has not fundamentally changed, which is the reason for the low survival rate of shrimp and crabs. Since 2005, the lotus pond farm selected for the experiment has applied the seawater pond bottom oxygenation technology and bleaching powder pond clearing technology, and has promoted the self-propagation technology of pike crab seed to the whole county. The use of bleaching powder or quicklime clear pond in pike crab farming has become one of the fixed technologies of the farm and one of the technical measures with a high survival rate of shrimp and crab farming in the past years. In the past few years, the promotion of the "pike crab - clam - Japanese shrimp" model has been good, but since 2016, there have been many diseases in clam farming, and the efficiency of breeding has gradually declined. According to the relatively good characteristics of the water exchange conditions in the pond, the farm immediately adjusted the breeding species, adopted the polyculture of pike crab and Japanese shrimp, and successfully absorbed and applied the anti-maim breeding technology of pike crab, achieving a double harvest of shrimp and crab.
2. Strictly control the elimination of moss. In general, after the seawater pond is released, or even before the seedlings are released, the pond moss multiplies in large quantities. Although moss has an effect on water purification, the impact on shrimp and crabs in ponds after the mass propagation and death of moss is relatively large. Therefore, when clearing the pond, all the moss in all corners of the pond must be killed. During the culture process, if a small amount of moss is found on the edge of the pond, it is immediately taken to reduce the water level and spray with bleaching powder to kill the moss. The time for a large amount of moss to appear in the anti-residue basket is 1 month after the pike crab catches the dry pond, so it is necessary to manually remove the moss in the anti-residue basket before clearing the pond to prevent the anti-residue basket from blocking.
3. Strictly control the three disease prevention links. First, from June 25 to July 15, the main prevention of shrimp and crab vibriosis, the drug uses "arc grams" and other prevention. Second, from August 30 to September 20, the main use of sprinkling compound iodine or quicklime disinfection water bodies to prevent shrimp and crab leukoplakia, erythematosis and yellow water disease. Third, from October 20 to November 10, the main use of sprinkling compound iodine disinfection water to prevent barracuda crab "milk disease". After disinfecting the water body with disinfectant each time, microecological preparations such as em bacteria and bacillus are used to adjust the water quality and change the substrate in time, so as to achieve relative stability of the algal phase and bacterial phase in the pond.