Pond ecological three-dimensional culture experiment of redfin oriental pufferfish-Japanese shrimp-Philippines-clams
Fund Project: Hebei Province Modern Agricultural Industry Technology System Featured Seafood Innovation Team Funded.
_ Li Buxian and others
Takifugu rubripes (Takifugu rubripes) in the mainland began in the early 1990s, after decades of development, the scale gradually expanded, the mainland Bohai Sea, Yellow Sea, East China Sea, South China Sea are cultured. At the same time, the rise of the redfin oriental pufferfish breeding industry has also led to the development of coastal related industries, such as export processing, shrimp farming (in puffer fish farming ponds), bait supply, the use of idle nursery workshops in winter, etc. However, the rent of aquaculture land has risen year after year, the cost of artificial and input products has increased year by year, the germplasm degradation of breeding varieties has led to frequent diseases, the economic value of breeding varieties is not high, and the lag of breeding technology has been threatening the sustainable development of the industry. Improving breeding technology is the only way to improve economic benefits. To this end, from 2017 to 2018, at the farm of Tsui Dong Tangshan Haidu Aquatic Food Co., Ltd. in Nanbao Town, Luannan County, the ecological three-dimensional culture of redfin oriental pufferfish-Japanese shrimp-Philippine clams was carried out in different densities to explore a new model of efficient culture technology suitable for seawater ponds in Hebei Province.
1 Materials and methods
1.1 Pond cleaning
The breeding test pond is located in the farm of Tsui Dong Tangshan Haidu Aquatic Food Co., Ltd. in Nanbao Town, Luannan County, and the selected pond has smooth inlet and drainage, no industrial wastewater, domestic sewage and fresh water inflow, and the bottom of the pond is sand mud bottom. Use the free time of breeding to drain the pond water, close the sunbathing pond, completely remove the sludge and weeds in the pond, trim the edge of the pond, strengthen the pond embankment, dredge the drainage channel, and maintain the pond water depth of more than 1.5m.
1.2 Disinfection and pest removal
10 to 15 cm of water is used for seedlings, and 750 to 1 500 kg/hm2 of quicklime is used to kill predators and improve the substrate.
1.3 Water inlet
About 15 days before the seedlings are released, the water is 60~80cm, and the filter is installed before the water inlet to avoid mixing with wild fish, shrimp and crabs, and the fertilization water is 30~45kg/hm2 or urea 15~30kg/hm2 to promote the reproduction of bait organisms.
1.4 Seed selection
Redfin Oriental Pufferfish: Choose overwintering fish species with no injury, sensitive response, consistent specifications, good fat fullness, and no parasites under microscopic examination, with a size of not less than 200g/tail.
Japanese shrimp: Select shrimp fry with a body length of more than 1 cm, a fat body, a lively swimming body, a transparent body, a neat size, no sticky dirt, and no white spot virus after testing.
Philippine clams: Select seedlings with uniform individuals, fresh color, healthy and unharmed, with a size of 1 400 to 1 600 grains/kg.
1.5 Seedling release time
Due to the ecological three-dimensional polyculture, the arrangement of the release time is different from the traditional single-species culture, and the Philippine clam seed should be released before the fingerlings and shrimp fry are released. Choose sunny, windless weather when releasing seedlings, and pay attention to the salinity difference between the nursery pond water quality and the pond water quality within 5 thousand points, and the temperature difference is within 3 °C. In this study, Philippine clam fry were stocked in early May, Japanese shrimp fry were stocked in mid-May, and pufferfish fingerlings were stocked at the end of May.
1.6 Stocking density
The stocking density of Philippine clams was 1 500 kg/hm2, the stocking density of Japanese shrimp was 45 000 fish/hm2, and the redfin oriental pufferfish were compared with three gradients of high, medium and low, of which the stocking density of redfin oriental pufferfish in 2017 was 1 500, 1 200 and 750 fish/hm2, respectively, as detailed in Table 1. According to the results of the test in 2017, the experimental breeding mode was adjusted in 2018. The stocking density of Philippine clams and Japanese shrimp remained unchanged, and the density of redfin oriental pufferfish decreased by the density difference, and the stocking density was 1 200, 1 050 and 900 fish/hm2, as detailed in Table 2.
Table 1 Stocking of seedlings in 2017
Table 2 Stocking of seedlings in 2018
1.7 Water quality management
Due to the small density of fish and shrimp stocking in this mode, in terms of water quality management, water quality is regularly regulated by photosynthetic bacteria, bacillus and other microorganisms, so as to improve the ecological environment of ponds and reduce the occurrence of diseases. The pond water quality is monitored regularly during the breeding process, and the water quality indicators are controlled within a reasonable range, the specific indicators are as follows: pH value 7.8 ~ 8.4, dissolved oxygen greater than 4 mg / L, hydrogen sulfide at the bottom of the pond is less than 0.01 mg / L, chemical oxygen consumption is less than 6 mg / L, water color yellow-green or tea brown, transparency 30 ~ 50 cm.
1.8 Feeding of bait
The bait of the redfin oriental pufferfish is mainly low-value marine fish, fed 1 to 3 times a day, according to the water temperature and body size, the daily bait is 3% to 20% of the fish body weight. To maintain the freshness of the bait, the bait is placed on a fixed food table, and the feeding situation is checked every day to adjust the amount of bait.
Shrimp bait is mainly based on bio-food and compound feed in the pond in the early stage, and full-price compound feed in the middle and late stages. Feeding is given 2 to 4 times a day, and the amount of feeding in the morning and evening accounts for 60% of the whole day. Initially, it is dropped at a depth of 50 cm, and as the shrimp grows, it gradually turns to the deep water area for feeding. The bait for Philippine clams is mainly basal biological food cultivated by fertile water in ponds before seedling release.
1.9 Disease control
In the process of breeding, "prevention is the mainstay, prevention and control are combined, and prevention is more important than treatment", focusing on ecological disease prevention. The use of prohydrogens, photosynthetic bacteria and other biological agents to improve the micro-ecological environment of water bodies, do a good job in the detoxification of fresh food and tools, and do not enter the water when there is a red tide in the sea.
1.10 Harvest
Fished at the right time according to the market, disease, weather, etc., the shrimp is harvested in September and sold. Before the water temperature drops to 12 °C, the redfin oriental puffer moved indoors for wintering or sale. Finally, Filipino clams were collected for sale.
1.11 Testing of water quality indicators
According to the Marine Survey Code Marine Chemical Element Monitoring (GB 12763.4-2007), the ammonia nitrogen (NH +4-N), nitrate (NO-3-N), nitrite (NO-2-N), phosphate (PO3-4-P), dissolved oxygen (DO) and other indicators in the water of the test pond were detected once every 15 days. The specific detection methods are as follows: ammonia nitrogen (NH +4-N) is oxidized by sodium hypobrominate; nitrate (NO-3-N) is reduced by zinc-cadmium; nitrite (NO-2-N) is used by diazo-azo method; phosphate (PO3-4-P) is used by phosphorus molybdenum blue spectrophotometry; dissolved oxygen (DO) is titrated by iodine titration. According to the Marine Monitoring Code Water Quality Testing and Analysis (HY003.4-1991), chemical oxygen demand (COD) was detected by the alkaline potassium permanganate method.
2 Results and analysis
2.1 Pond ecological culture test out of the pond situation and production results analysis
From Table 3 and Table 4, it can be seen that the survival rate of the redfin oriental pufferfish in the test pool is 1.8% higher than that in the control pool, and the average yield is 1 152 kg/hm2, which is 99 kg/hm2 higher than that in the control pool. The survival rate of redfin oriental pufferfish did not change significantly with the increase of stocking density, but there was a large difference in growing regulations and production. The higher yield specifications of the redfin oriental pufferfish with a drop density of 1 200 fish/hm2 and 750/hm2 have a higher than the specific density of 1 500 fish/hm2, which directly affects the sales price, but the lower yield of 750 fish/hm2 results in lower production value. Overall, a stocking density of 1 200/hm2 is more appropriate.
Table 3 Out of the pond in 2017
Table 4 Analysis of production results in 2017
Note: The production of Philippine clams averages 3 600kg/hm2 and sells for $5/kg.
The yield of redfin oriental pufferfish in the control pool in 2018 was 85.5 kg/hm2 lower than the average yield of the test pool. The culture size of the redfin oriental pufferfish varies with the release density is not obvious, but the output value of the stocking of 1 200 / hm2 and 1 120 / hm2 redfin oriental pufferfish is higher than that of 900 / hm2. See Table 5, Table 6.
Table 5 Outflows in 2018
Table 6 Analysis of 2018 production results
Note: The production of Philippine clams averages 3 600kg/hm2 and sells for $5/kg.
2.2 Detection results and analysis of conventional water quality indicators for ecological pond aquaculture
The corresponding indicators of DO, COD, NO-3-N, NO-2-N, NH + 4 -N, PO3-4 -P and the corresponding indicators in the control tank in the test cell were basically the same in the average change trend of the aquaculture production process, but the DO in the test cell was slightly higher than that in the control pool in the same period, the COD, NO-3 -N and NO -2 -N in the test cell were lower than the control pool, and the NH + 4 -N and PO3-4 -P in the test cell were not significantly different from the control pool. See Figure 1-Figure 6.
Figure 1 Pond DO change comparison
Figure 2 Pond COD variation comparison
Figure 3 Pond NO -3 -N variation comparison
Figure 4 Pond NO-2-N variation comparison
Figure 5 Pond NH+4-N variation comparison
Figure 6 Pond PO 3-4 -P variation comparison
Redfin Oriental Pufferfish is a ferocious carnivorous fish, after polyculture with Japanese shrimp, the growth rate of healthy Japanese shrimp is accelerated, and the frail and diseased Japanese shrimp is preyed upon by redfin oriental pufferfish. After the residual bait and manure are decomposed by microorganisms in the pond, they can be used as fertilizer for phytoplankton, and the polyculture Offictic Philippine clams feed on small phytoplankton and suspended organic detritus, which can prevent organic pollution of the pond water, maintain stable water quality, and improve energy conversion rate. It has made full use of the biological characteristics of different species such as fish, shrimp, and shellfish, reduced the spread of diseases, purified the water quality, reduced the discharge of pollution, and achieved obvious ecological effects.
3 Summary
The results of the culture experiment showed that the redfin oriental pufferfish, Japanese shrimp and Philippine clams were stocked at a density of 1 200 fish/hm2, 45 000 fish/hm2 and 1 500 kg/hm2 respectively, and when the pond ecological three-dimensional culture was carried out, compared with the single redfin oriental pufferfish in the pond, it was more conducive to improving the production capacity of the pond, which could promote the transformation of redfin oriental pufferfish culture to ecologically efficient culture, and then radiate to drive the marine pond culture in the region to a new level, improve the utilization rate of ponds and increase the income of fishermen.