A preliminary study on the effect of circulating water system in the greenhouse of American anchovy and relay culture in greenhouse soil ponds
_Meng Qinghui, etc
Zhejiang Provincial Department of Agriculture and Rural Affairs "Three Rural And Six Parties" Science and Technology Collaboration Project - Anchovy Brackish Water Aquaculture Technology Development and Demonstration, Zhejiang Aquatic Industry Technology Innovation and Extension Service Team, Zhejiang Province "Modern Agriculture - Ecological Fisheries Technology Innovation Promotion and Disease Prevention and Control" special support.
1 Introduction
American anchovies (A l o s asapidissima), also known as American herring, belongs to the order Clupeiformes, Clupeidae, herring (Alosa), is a typical river-laying fish, the original main distribution area is located in the rivers and oceans on the west coast of the Atlantic Ocean in North America, is one of the important economic fish in North America. As a wide temperature retrospective migratory fish, American anchovy has the characteristics of tender and delicious meat, high nutritional value, high market positioning and good price. At present, the culture mode of American anchovy mainly includes greenhouse culture, cage culture, pond culture, etc., and there are also PVC painted canvas fish ponds, polyculture with other species, and factory-earth pond/cage two-stage culture.
In this paper, in the brackish water basin environment of the estuarine, the experiment of relay culture based on greenhouse circulating water system and greenhouse soil pond was explored, which aims to promote the development of American anchovy culture model, enrich the american anchovy culture technology and promote the green and sustainable and healthy development of its aquaculture industry.
2 Materials and methods
2.1 Test sites and facilities
The test site is the Xiaoshan Comprehensive Test Base of Zhejiang Aquatic Technology Promotion Station, located in the sixth section of The Waiken outside Xiaoshan, Hangzhou, with convenient transportation; The water quality of the base is brackish water, and the salinity is stable at 0.8‰ to 1.5‰ all year round, and the water quantity is sufficient.
The circulating water system of the breeding greenhouse is a steel structure greenhouse, the roof is a color steel tile sandwich board combined with a transparent sun panel, and the high temperature season is covered with a shade net to avoid excessive water temperature and strong light. In this test, the greenhouse cement pond specifications are 5 m long, 4.4 m wide, 1.1 m high (the maximum water level is 1.0 m), and the aquaculture water volume is about 22 m3; in order to adapt to the linear swimming characteristics of American anchovies, the four corners of the pond are cut into a circle with bricks; the bottom of the pool is high, the middle bottom is set, and the sewage outlet is set at the lowest point; A 1.0m high overflow pipe is installed at the outlet of the drainage pipe. The circulating water system is equipped with 1 set of 2.2kW bottom aerator, each test cell is equipped with 6 nano-aeration plates with a bottom diameter of 60cm, and the inlet pipe is connected to 1 set of ultraviolet sterilizers; at the same time, it is equipped with 3 sets of generator sets and geothermal heating equipment; Aquaculture tailwater is fully integrated into the tailwater integrated treatment system.
For the relay breeding of the greenhouse soil pond, a thin film steel frame greenhouse mud bottom pond was selected, with a pond area of 1.85 mu and a water depth of 2.0 m. Vents are set around the greenhouse, in the high temperature season to avoid excessive water temperature, too strong light, the part above the vent is covered with a shade net, and the shade net area is about 70% of the pond area to ensure that the air can be fully circulated and the light intensity can be reduced. Tutang pond is equipped with 2 sets of 1.5kW waterwheel aerators, 1.1kW bottom aerator, and 18 nano-aeration disks to ensure that the dissolved oxygen ≥ 6mg/L of each pond water body; All tailwater is recycled after comprehensive treatment of the tailwater system of the base.
2.2 Test Animals
American anchovy fry were purchased from a farm in Suzhou, Jiangsu Province, with an initial size of 4.78 cm, an average weight of 0.77 g/tail, and 3 cement ponds stocked in the circulating water system, with a stocking density of 1,100 fish/pond and 55 fish/m3 per unit of water body. Seedlings are required to be neat in size, lively and swimming, with a strong physique, no injury, no disease, and no deformity. The circulating aquaculture period was 273 d, after which it was merged and transferred to the greenhouse soil pond to continue the breeding for 150 d.
Figure 1 Growth and water temperature trend of indoor circulating water and greenhouse soil pond relay culture of American anchovy
2.3 Aquaculture management
2.3.1 Stocking of seedlings
After the cement pool is filled with water, it needs to be soaked twice, soaked for 7 days, then washed and drained; Soak again for 3d and sterilize with bleaching powder. Inject fresh water 1d before seedling release and filter with a sieve mesh of more than 100 mesh. The initial water depth is about 0.6m, the bottom aerator plate is evenly distributed, and the dissolved oxygen of the water body needs to be ≥6mg/L.
Transporting seedling vehicles need to use air-conditioned vehicles, transported with oxygen in circular barrels with a diameter of 1.2m, maintaining a dissolved oxygen volume of about 8mg/L, and transporting water temperatures of about 18 °C. The seedling stage of American anchovy is relatively delicate, and it is necessary to concentrate on temporary rearing for 1 week after long-distance transportation, and then feed the fry after emptying the stomach and intestines, and do not feed on the same day; A small amount of feeding begins on the 2nd day, after which the amount of feeding is gradually increased.
2.3.2 Feed feeding
In this test, before the anchovy size < 100g/tail, a certain brand of California perch puffed compound feed was fed, the specification > 100g/tail, <450g/tail, in order to reduce the cost of breeding, the size > 450g/tail, turned back to the California perch puffed compound feed for feeding.
California perch puffed compound feed test material is based on imported American white fish meal, soybean protein, peanut meal, etc. as the main protein source, and fish oil, soybean oil and so on as the main fat source. The measured values of the basic nutritional composition of the feed were: crude protein 46.3%, crude fat 8.3%, crude ash 12.6%, calcium 2.8%, total phosphorus 1.9%, and lysine 3.2%. In the medium term, the puffed compound feed of red-billed red crab will be appropriately fed to reduce costs, and the measured values of basic nutritional composition are: crude protein 43.0%, crude fat 5.0%, crude ash 16.0%, calcium 1.0 to 4.0%, total phosphorus 1.0%, and lysine 2.3%.
At the beginning of the breeding test, feeding was carried out in accordance with a small number of meals, and the light should not be too strong when feeding, and the total amount of daily feeding was controlled at about 8.0% of the fish's body weight. Enter the high temperature period (water temperature above 28 °C), change to 2 times a day feeding, the daily feeding amount of 1.5% to 2.0% of the fish body weight; The eye-to-eye satiety method shall prevail.
Table 1 Stocking and temporary rearing of seedlings
2.3.2 Water quality management
In the early stage of indoor circulating aquaculture, the daily water turnover is controlled at about 20% of the pond water; Entering the high temperature period, the daily water turnover increases to about 30%; After the water temperature drops below 25 ° C, the American anchovy enters the peak of feeding, and it is necessary to increase the amount of water exchange, and the daily water change control is more than 40%. The aquaculture water is sterilized by ultraviolet sterilization and then entered into the pond, and the inlet and drainage outlet are independent. The bottom of the pool is cleaned by siphoning, 2 to 4 times a week according to the situation, to ensure that the bottom of the pool, the wall and the bottom aerator plate are clean. The water quality indicators are tested daily to ensure the stability of the aquaculture water body, the dissolved oxygen ≥6mg/L, the pH value is 8.2~8.8, the ammonia nitrogen ≤ 0.8mg/L, and the nitrogen nitrite ≤ 0.2mg/L. In winter, in order to ensure the normal feeding of the test fish, the heating equipment is started. A special person needs to be assigned to work for 24 hours.
In the water quality management of the relay pond in the greenhouse, after the transfer of anchovies, it is necessary to replace new water every day, the summer water temperature is too high to fill the groundwater to reduce the pond water temperature, the daily water exchange is controlled at 20 to 30% of the pond water, and the biological agents and substrate improvers are sprinkled every 7 to 10 days, the biological agents are mainly bacillus and EM bacteria, and the bottom is mainly potassium persulfate to ensure that the water quality is stable and the substrate is clean. The dissolved oxygen and pH indexes of the pond were detected using the Cima AR8010 portable dissolved oxygen meter and the Nanjing Tean portable parameter water quality analysis box, the ammonia nitrogen was detected by the Nahren's reagent colorimetry, and the nitrosinous nitrogen was detected by the sulfa reagent spectrophotometer colorimetry, which was monitored regularly.
2.3.3 Disease control
Adhere to the principle of "focusing on prevention and combining prevention and control"; Regularly add immunogly polysaccharides, enrofloxacin, etc. to the feed, and pour povidone iodine solution to effectively increase the immunity of the fish body and prevent the occurrence of bacterial diseases. Found sick fish in time to catch and treat to prevent infection. During the trial, there were no large-scale disease outbreaks.
2.3.4 Dragnet training and relay
In the process of breeding, in order to make the American anchovy more reliable in the transfer relay process, in the process of circulating water culture in the American anchovy greenhouse, the net training and the forging operation of the sample are carried out. To prevent abrasions from American anchovies, the mesh is a specially tailored polyester soft mesh. Before operation, sprinkle anti-stress products such as vitamin C to reduce fish stress. A total of 3 exercises were carried out before the relay, and the first time the net exercised the fish to hit as far as possible in the range of the net, the time was 10 min, and then the fish were released back into the pond; The second and third drag-net exercises can gradually reduce the range of fish in the net for about 10 minutes, during which the aerator needs to be turned on. Before relay transfer, it is necessary to stop feeding for more than 24 hours to ensure that the fish body is in a state of gastric emptying. During the relay transfer process, the whole process of water needs to be operated, and the fish body is soaked with 5‰ salinity during transportation.
Table 2 Sampling status of relay test
2.4 Indicator calculation
Fish body measurements are carried out monthly during the culture period, and the yield is measured at the end of the culture. The relevant indicators and calculation formulas are as follows:
(1) Survival rate SR(%) = 100× (number of test fish at the end (g) / number of test fish at the beginning (g));
(2) The specific growth rate S G R( % / d ) = 100 × [Ln-end mean weight (g)-Ln initial mean weight (g)]/feeding days (d);
(3) Feed coefficient FCR = 100× feed intake (g)/(end weight g- primary weight g).
3 Results
After 273d of greenhouse circulating aquaculture, the overall health of the American anchovy is good. The survival rate of each experimental group was between 82.1% and 89.7%, with the highest pool A2 and the lowest pool A3, with an average survival rate of 86.7%. (For specific aquaculture sampling results, see Tables 2 and 3).
Table 3 Relay test culture table
Table 4 Measurement of production costs of relay culture
The American anchovy relay was then transferred to the greenhouse soil pond for further breeding, and the average size was 236.0 g/tail and the average length was 30.2 cm. The transfer time of the Tutang relay is April 3. Three circulating pools are combined for a total of 2,861 tails. After 151 days of breeding, the average individual size was 520.5 g/tail, and the average total length was 37.6cm, reaching the market specifications. The yield per unit of production measurement was 682.4kg/mu. According to the statistics of dead individuals, the survival rate in the process of greenhouse soil pond relay was 82.5%, and the comprehensive survival rate of the whole process was 71.5%.
As shown in Figure 1, the American anchovy grows fastest at an average water temperature of 18 to 24 °C, and the time is about April to June and September to October of each year. The water temperature of the greenhouse in Zhejiang in winter needs to be maintained above 15 ° C, in order to ensure the winter breeding and growth of anchovies, the summer needs to be cooled down treatment, the use of water air conditioning for water temperature control, can achieve indoor circulation flow culture system summer anchovy water temperature control below 28 ° C, in the greenhouse pond breeding process, by using groundwater injection, the use of shade nets, ventilation and other measures, the summer water temperature can be maintained below 29 ° C, the normal growth of anchovies remains good. The test demonstrated the feasibility of american anchovies using a greenhouse cement pond circulating water system and greenhouse earthen pond relay.
The specific growth rate of American anchovy in the whole culture process was 1.34, and the comprehensive feed coefficient was 2.57. As shown in Table 2, in the breeding process, the total cost is 95,200 yuan, of which feed costs, seed fees, electricity costs, labor costs, etc. are the main components of the breeding costs, accounting for 92.1% of the total cost, and feed costs are the most, accounting for 42.0%. The production cost per kilogram of fish is 77.54 yuan / kg, and according to the market price of the sale in the current year, the total output value of the catch is 122,700 yuan.
American anchovy is introduced into China under the endangered situation of anchovy in the Yangtze River, and after years of development, it has become one of the precious breeds in China. In the natural state, plankton, especially plankton, sometimes eat small fish shrimp and algae and other kinds of food fish, like to swim in the water body non-stop, the demand for dissolved oxygen in the water body is relatively large, and with the continuous increase of growth specifications, the requirements of the American anchovy for living space are getting higher and higher.
At present, the main breeding mode of American anchovies, indoor circulating water factory culture, more is to improve the breeding density and breeding product quality way to reduce operating costs, but factory culture and cement pond culture, with the size of the fish body is getting larger and larger, it is easy to cause diseases such as scraping and scalding during the swimming process of the fish because of the high density, which will also affect the sales of adult fish, and the high density of the breeding environment, dissolved oxygen and other requirements are also getting higher and higher, and the breeding is difficult.
Simple pond culture, winter can not overwinter, the temperature repeatedly also easy to cause death and low survival rate, summer high temperature season is easy to cause visceral hemorrhage, water temperature is too high will also cause fish to stop facilities, growth stagnation and other situations.
This model attempts to use the indoor circulating water system and the greenhouse soil pond relay culture mode, that is, first in the indoor circulating water system to breed for a period of time to a certain size, and then merge and transfer to the greenhouse soil pond to continue to breed until the adult fish are sold. The survival rate of indoor circulating aquaculture can reach 86.7%, the survival rate of greenhouse soil pond aquaculture can reach 82.5%, and the comprehensive survival rate can reach 71.5%. Compared with the whole indoor circulating aquaculture survival rate of the base, the survival rate of the whole indoor circulation aquaculture in this base is increased by more than 10%, and the growth cycle of the same specification is shortened by 30 days.
The relay culture model helps to solve the problems of larger fish body size, high density and high cost of circulating water aquaculture in the late stage of Anchovy culture in the Americas, which has a good prospect for large-scale promotion of the industry, and has important reference significance for shortening the breeding cycle, reducing the cost of breeding, improving the survival rate, and promoting the sustainable and healthy development of the Anchovy industry.