American Shad Lecture Series Artificial breeding technology of American shad
Shi Yonghai, etc
The breeding scale of continental American shad is expanding day by day, mainly concentrated in the Yangtze River Delta, Hubei, Sichuan and other places, and the annual stocking amount of seedlings is 2.5 million ~ 3.5 million. Common modes of breeding anchovy include intensive culture, large surface cage culture, shading pond culture, etc. In recent years, greenhouse structure pond aquaculture has gradually emerged in the Yangtze River Delta region, which has the advantages of low breeding requirements, low energy consumption, controllable cost and convenient management. The greenhouse structure pond culture model of American shad is introduced as follows.
1. Breeding conditions
1. Water source
The water source requires convenient water, salinity 0~12, pH 7~10, and dissolved oxygen to be kept above 5 mg/l.
2. Pond conditions
The pond selection requires a quiet environment, an area of 2~5 acres, a sediment bottom, and a water depth of more than 2 meters. There are independent inlet and drainage systems, the water quality of the pond is good, and the aquaculture discharge water should comply with the relevant provisions of the "Freshwater Pond Aquaculture Water Discharge Requirements" (SC/T 9101-2007) and "Marine Aquaculture Water Discharge Requirements" (SC/T 9103-2007). The water inlet should be filtered by a 60-mesh sieve tulle, and the drain should be equipped with a purse seine mesh of 2 mm × 3 mm and a 40-mesh gate. Each pond should be equipped with 1~2 sets of 1.5~3 kW impeller aerators.
Two adjacent ponds are selected to build greenhouses, the span of the pond greenhouses is not more than 100 meters, the steel structure of the pond frame between the ponds is girdered, and the flexible steel wire rope is laid to the pond ridges on both sides, and fixed on the ground anchor to form a scaffold, and the top is covered with a shading film with a shading rate of more than 90% (Figure 1). Ponds are thoroughly disinfected before use with conventional disinfectants such as bleaching powder or quicklime.
Figure 1 Shading pond
Second, basic food biological culture
Basic food organisms need to be cultivated before stocking of summer flower fingerlings. According to the stocking time, add 0.5 meters of new water 5~7 days in advance, and gradually increase the water level to 2 meters; turn on the aerator at noon on a sunny day for 1 hour, and it can not be turned on at night. When the water temperature is 25~30 °C, the water color becomes thicker after 3~5 days, and 5~7 samples are taken at different points in the pool with a beaker at 6~10 days to detect cladoceres, copepod larvae and other food organisms, and when the biomass reaches 20~40 / liter, fish fry can be stocked.
3. Stocking of fingerlings
1. Summer flower fingerlings (0+ years old) stocked
Summer fingerlings are stocked from mid-May to mid-July, choose to stock in the morning, and the aerator should be turned on before the fingerlings go to the pond. The length of the fingerlings is 40~60 mm, and the stocking density is 1 500~2 500/mu. When the fingerlings go down to the pond, the pond water should be added to the transport container at the upper wind of the pond, and the fingerlings should be allowed to adapt for 1~2 minutes before stocking. Fingerlings are domesticated and fed compound feed after 10 days of stocking. The characteristics of the different transport methods of the American anchovy species are shown in Table 1.
Table 1 Characteristics of the mode of transport of American anchovy summer flower fingerlings
Specific transportation mode suggestions: short-distance transfer if the transportation time is less than 0.5 hours, especially the on-site transportation stocking, you can choose 20~50 liters of barrel shading transportation, the density is 1~2 tails / liter; For transportation with a transportation distance of 100~200 kilometers and a time of 2~3 hours, you can choose a water truck (vehicle-mounted water tank) or oxygen bag insulation transportation, and the survival rate of transportation is higher (>95%); Long-distance transportation can be transported by oxygen bags in aviation insulation foam boxes, and the survival rate of transportation is particularly high (99%). Adding some anti-stress agents to transport water bodies can reduce the stress response of American anchovy fingerlings, reduce transport damage and death, etc.
2. 1+ year-old fingerlings stocking
When the water temperature in the open pond rises above 15°C, 1+ year-old fingerlings can be stocked. Shad 1+ year-old fingerlings are generally transported over short distances, such as on-site dragnets. When stocking and transshipment, 20~50 liter drums with water shading are used for transportation, and the transportation density is 15~20 tails/barrel. When stocking, turn on the aerator in advance and measure the water temperature, the temperature difference does not exceed 2 °C, the body length of the stocked fingerlings is 15~20 cm, the weight is 60~100 grams, and the stocking density is 800~1000 / mu.
4. Feed feeding
The feed fed is a floating puffed compound feed, and the specific parameters are shown in Table 2. Feed is fed once a day in the morning and afternoon when there is no direct sunlight, and the feeding amount is subject to 2 hours of feeding. The feed should be placed in the feed box, which can be made of floating materials (wood, PVC, bamboo, etc.), with a specification of 1.5 meters × 2 meters, and a frame height of 10 cm (5 cm above water and 5 cm underwater).
Table 2 Comparison of shad size and feed size
5. Water quality regulation
1. Pond shading
After the temperature rises in summer, the surface water temperature of the pond reaches 24°C from 16:00 to 17:00 and after 1 continuous week, the shade film is pulled above the pond greenhouse, and the two ends can be ventilated. When the surface water temperature of the pond from 16:00 to 17:00 after autumn drops to 24~25°C for 1 week, remove the shading film. In the Yangtze River Delta region, by building awnings, the temperature of the pool water can basically be maintained below 30 °C.
2. Change the water
For 0+ year-old fingerling culture, change 1/3 of the water every two weeks, and reduce the frequency of water change and water change when the water temperature of the water source exceeds 32°C. When the temperature of the pond water is < 28°C, the water is changed once every 14 days, and the water change is 1/3 of the whole pool water; when the pool water temperature is > 28°C, try to choose a small number of water changes in the early morning when the outside water temperature is relatively low, and the water change is 1/5 of the whole pool water. Conditional units can gradually switch to seawater after fingerling stocking, and slowly transition from fresh water to marine aquaculture environment, simulating the natural living environment of American shad.
3. Oxygenation
Turn on the aerator from 18:00 to 21:00 every day, shut it down from 5:00-6:00 the next day, the start time is 8~12 hours, and the start time is increased by 1~2 hours after shading the pond. In case of bad weather such as bad weather or continuous rain, the start-up time should be extended to ensure that the dissolved oxygen in the pond water is higher than 5 mg/l.
6. Daily management
Daily management pays attention to water temperature, dissolved oxygen monitoring and water color observation, and measures should be taken to solve problems in time. Insist on patrolling the pond once a day in the morning and evening, measure the water temperature once a day in the morning and afternoon, pay attention to the feeding and activities of fish fingerlings, clean up the unfinished feed in time and adjust the feeding amount to achieve accurate feeding. Through scientific feeding, regulating water quality, keeping the environment quiet, reducing stress response and other measures, ecological disease prevention can be achieved. Sick fish and dead fish should be removed in time, and daily breeding records should be made, and records should be kept for more than 3 years.
7. Dragnet to catch up
1. 0+ year-old fingerlings are caught in the nets
When the water temperature drops below 15°C, it needs to be dragged and transported into the wintering link. Before transportation, exercise 2~3 times with polyethylene mesh dragnet. One day before the net is caught, feed is stopped. After starting the net, the upper limit of the number of fish in the net enclosure is controlled at 1 000~1 500, and the retention time of the purse seine is less than 30 minutes; When the number of ponds is less than 1500, the whole pond is dragged.
2. Adult fish are sold in dragnets
When the anchovy reaches 500 g/tail, check the fullness of the adult fish and put it on sale. The dragnet exercise method refers to 0+ year-old fingerlings. When pulling nets for sale, first place the net at 1/3 of the pond surface, the upper limit of the number of fish in the net fence is controlled at 300~400, and the retention time of the purse seine is less than 30 minutes. When the number of ponds is less than 400, the whole pond is pulled and sold one after another.
The transport water tank is round (or nearly circular), the diameter is greater than 2 meters, the height is 1.2 meters, the transportation water level is 70~75 cm, the entire water tank is covered during transportation, and nanotubes are used for pure oxygen oxygenation. When the breeding water temperature is lower than 24 °C and the shipping water temperature is lower than 20 °C, the shipping density is 35~40 tails/m3; When the breeding water temperature is 24~28 °C and the shipping water temperature is 22~25 °C, the shipping density is 25~30/m3; When the temperature of the aquaculture water is higher than 28 °C, it is not suitable for sale and transportation. Concentrated sea crystal can be appropriately added to the transportation water, and the salinity can be adjusted to 5~8. The transportation time is controlled in 3~5 hours, and the survival rate of transportation can reach more than 90%.