1. Fish pond cleaning and disinfection
1.1 Dredging of fish ponds
After 1 year of rearing of fish, shrimp, crabs, etc., a large amount of food residues and excrement are often deposited at the bottom of the pond, and these organic wastes are decomposed and decomposed to form silt at the bottom of the pond, and the silt is a good medium for bacteria.
Therefore, when the silt is deposited to a certain thickness, it must be removed in time.
The increase in the incidence of hemorrhagic diseases of silver crucian carp and bacterial diseases such as giant shrimp and green shrimp is related to the failure to clean up the silt at the bottom of the pond in time.
According to the experience of foreign shrimp farming, high-density shrimp farming, it is best to remove the 1 layer of floating mud at the bottom of the pond every year, and its purpose is also to remove the nutrient source required for bacterial breeding.
In addition, there are a large number of parasite eggs and spores in the silt, and digging up excess silt can also greatly reduce the incidence of invasive diseases.
Generally speaking, the thickness of the silt at the bottom of the pool is only about 15 cm.
This not only allows the water body to have a certain degree of fertility to cultivate plankton, meet the needs of aquaculture for natural food, but also reduce the breeding ground and bacterial density of pathogenic bacteria.
Therefore, every year when the fish pond is cleaned, the excess silt at the bottom of the pond must be removed.
1.2 The bottom of the pool is exposed to sun and ice
The bottom of the pond needs to be exposed and frozen for about 15 days a year, one is to improve the soil quality of the bottom of the pool, and the other is to reduce the density of pathogenic bacteria and parasite eggs and spores in the silt at the bottom of the pool.
The incidence of cultured diseases has decreased significantly in the exposed and frozen fish ponds at the bottom of the pond.
However, if the bottom of the pond is dried for too long, it is easy to cause grass shortages.
1.3 Drug clearing pond
Quicklime clearing pond can effectively kill pathogenic bacteria, parasites and spores, etc., and can improve the soil quality of the bottom of the pond.
2. Stocking robust seedlings
Selection criteria: robust physique, no deformity seedlings, and uniform specifications. There is no inflammation on the surface of the body, fins or appendages, and there are no abnormal conditions such as rotten gills and white liver.
The seedlings swim (or crawl) flexibly and are not pathological. Units or individuals with the capacity can use microscopes to take samples of the body surface, gill liver and other parts for microscopic examination, and there should be no parasites or pathogenic bacteria.
For Giant River Prawns and Penaeus vannamei, shrimp fry that have been quarantined and do not carry the virus should be purchased.
Third, the seedlings are stocked with medicinal baths before stocking
For fish, a medicinal bath of potassium permanganate solution of 15-20 mg/kg can be used for 15 to 20 minutes, depending on the tolerance of the fish to the drug.
Before the crab species are stocked, at the water temperature of 5 to 8 °C, soak with potassium permanganate 20g/m3 for 3-5 min, or disinfect with a 3% to -5% salt water solution medicinal bath to kill bacteria and parasites on the surface of the river crab.
After the shrimp fry entered the pond, the whole tank was sprinkled with dibromohydantoin and the like (concentration of 0.3 mg/kg).
4. Disinfection of food stations or food fields
Use about 250g of bleach powder to water and sprinkle it around the food table or food field, generally twice a month from April to September;
Light consumption of lime can effectively inhibit pathogenic bacteria, and can timely replenish the calcium in the body, so that the water body is alkaline all year round. This is especially important for the cultivation of special crustaceans.
Quicklime light elimination method:
Conventional fish ponds generally have a water depth of 15kg/mu per meter, and special aquatic products (such as mandarin fish, shrimp, crabs, etc.) are generally 7kg/mu per meter.
Fifth, choose high-quality matching bait
Uniform particles, good stability in water, comprehensive nutrition, low bait coefficient, etc.;
And the addition of food attractants and stable vitamin C, etc., to promote the feeding, digestion and absorption of farmed species, promote their growth, enhance disease resistance, improve survival rate.
It is necessary to pay attention to the scientific feeding of feed, do not feed a single feed, and avoid nutritional diseases caused by the lack of certain nutrients.
For example, in shrimp and crab farming, in addition to feeding animal bait and full-price compound feed, sufficient plant feed should also be ensured.
Sixth, the use of biological regulation of water quality
Biological regulation of water quality ensures a good ecological environment, thereby improving the physique and disease resistance of fish, shrimp, crabs and other aquatic products.
Biological control of water quality can be carried out by planting aquatic weeds, stocking snails, adding beneficial bacteria, and cultivating plankton (such as fertilization).
The corresponding biological regulation method can be selected according to the cultured species.
The photosynthesis of phytoplankton can enrich the water body with oxygen, reduce the formation of toxic substances such as ammonia nitrogen and hydrogen sulfide, create a good ecological environment, and inhibit the breeding of pathogenic microorganisms.
Regular administration of photosynthetic bacteria with beneficial active microbial preparations, compound live bacteria biological water purifiers (Bacillus), etc.;
They can quickly and completely decompose organic matter into inorganic nutrient salts available to single-celled algae in water bodies.
Reduce the pollution of organic waste, which is harmless to the breeding species, and at the same time can rapidly multiply and grow in the water body to form a dominant flora.
Through food, place competition and secretion of antibiotic-like substances, directly or indirectly inhibit the reproduction and growth of harmful bacteria.
Biologically regulated water quality reduces pool water discharge, thereby reducing pollution from outside water sources.
Research and practice have proved that improving the substrate through large-scale irrigation and water exchange methods has a poor effect, which will cause discomfort and stress disease in the growth of Penaeus vannamei.
Seven, supporting aeration machinery
Through the water pumping effect of the aerator, the dissolved oxygen of the water body is increased, so that the organic matter in the substrate and the excreta and residual bait of the fish and shrimp in the water are fully oxidized and decomposed into inorganic nutrient salts required for single-celled algae;
Reduce the pollution of organic waste and maintain good water quality conditions to avoid the occurrence of disease-inducing stress conditions.
Eighth, grasp the law of disease incidence
Grasp the pathogenesis of certain aquaculture diseases, regularly administer drugs or feed medicinal bait in water bodies, kill germs, and reduce pathogenic factors;
However, it is necessary to pay attention to the antagonistic and synergistic effects of the drug, and can not be used simultaneously with microbial preparations.
For example, for hemorrhage in silver crucian carp, disinfect the water body every 15 to 20 days during the onset season and feed the medicinal bait for 2 to 3 days.
bibliography
Tang Kaihua, He Baofu Occurrence and prevention measures of aquaculture diseases[J]Modern Agricultural Science and Technology, 2008 (15): 294 , 297.