How to Farm Shrimp in Freshwater? A Full Breakdown of the Key Farming Techniques
Along with the continuous rise in living standards in our country today, the demand market for shrimp in our country is growing larger and larger, and freshwater shrimp farming techniques are relatively popular in the current shrimp farming industry, and are also adopted by many shrimp farmers. As our country's aquaculture technology is constantly updated and developed, farmers must keep innovating and improving on existing techniques in order to achieve certain results.
Freshwater Shrimp Farming Techniques
I. Habits of the Shrimp
The freshwater prawn (Macrobrachium nipponense) lives widely in lakes, ditches and rivers, and most prefers to inhabit shallow waters with abundant aquatic plants. It is an omnivorous animal; the larvae mainly feed on plankton, while adult shrimp mainly feed on the decayed stems and leaves of aquatic plants. Freshwater prawns generally mate and spawn between July and September, laying 800 to 1200 eggs each time. Because the fertilized eggs receive good protection from the mother, the natural hatching rate is above 92%. After 3 to 4 molts, the larvae become juvenile shrimp. Juvenile shrimp need only 2 to 3 months to mature and spawn. Freshwater prawns have strong reproductive capacity; after a female shrimp spawns and hatches, it can quickly spawn again.
II. Farming of Freshwater Prawns
There are two methods for farming freshwater prawns: one is to directly stock freshwater prawns, with 500 to 800 female shrimp and 300 to 500 male shrimp per mu, and this should be stocked at the end of April or the beginning of May. The second is to stock artificially bred juvenile shrimp: first use a pond of about one mu as a breeding pond; before the Beginning of Summer, catch 10 to 12.5 kg of egg-bearing parent shrimp from an outside river, select robust individuals with a large egg load and put them into the pond, and place aquatic plants or poplar roots in the pond. During the spawning period, feed one small bucket of soybean milk each morning (about 1 kg of soybeans), then throw in one bucket of slurry water of rapeseed cake or sugar dregs (about 5 kg dry matter). Twenty days after the juvenile shrimp hatch, 250 juvenile shrimp can be produced. When freshwater prawns are raised artificially, the yield per mu can reach 15 to 25 kg, and high yields can reach 40 to 50 kg.
III. Bait Supply
Freshwater prawns have a relatively omnivorous diet. When raised artificially, various artificial feeds can be fed, such as river snails, silkworm pupae, fly maggots, fish meal, etc. Plant-based feeds include soybean cake, rice bran, wheat bran, distillers' grains, etc. The best time to feed is around 5 p.m., and the bait can be evenly scattered around the shrimp pond in an appropriate amount, so as to prevent the freshwater prawns from killing each other due to hunger.
IV. Artificial Farming Pond
To farm freshwater prawns artificially, a shrimp pond must be built. An ordinary fish pond can be used as a shrimp pond, with an area of 2 to 6 mu, a water depth of 1.2 to 1.5 m, and a flat sandy-mud bottom with not too much silt. The shrimp pond should be close to a water source and convenient for drainage and irrigation. Freshwater prawns have poor swimming ability, so some submerged plants such as shrimp algae should be grown in the shrimp pond to provide habitat for the shrimp, but the area should not exceed 25% of the water area; branches can also be placed in the pond for the shrimp to hide in, preventing losses of shrimp fry. Before stocking, tea seed cake, croton, bleaching powder, derris powder or other drugs are usually applied to kill harmful fish and large aquatic insects in the pond and prevent predators from eating the shrimp. Shrimp ponds should be patrolled and managed more intensively during normal times, to prevent the pond banks from collapsing or leaking, or water birds and water rats from preying on the freshwater prawns. Once a large number of juvenile shrimp are seen jumping, swimming on the water surface, or crawling at the pond edge, it indicates that the dissolved oxygen in the pond is on the low side and metabolites are too high, which will cause mass death of the freshwater prawns, and the water must be changed immediately to increase oxygen.
Points to Note in Crayfish Farming
1. Strictly clear and disinfect the pond. The shrimp pond should be exposed to the sun for 15-20 d, until the pond bottom surface is dry, hard and cracked. Two weeks before stocking, first add a small amount of water, dissolve 100 kg of quicklime per mu and evenly scatter it on the pond bottom, and use manual methods to rake through the silt at the pond bottom; after a few days, add water to cover the entire pond bottom, then splash the whole pond with 2 kg of chlorine dioxide per mu and 50 kg of soaked rapeseed cake respectively; after 2-3 d, drain the disinfection water, dry the pond for 3-5 d, and then inject new water after filtration.
2. Improve the pond conditions for crayfish farming. The basic conditions of the farming pond, such as the environment, area, water depth, and water quality indicators, must comply with the GB/T18407.4 standard. The water source must be free of any pollution, with sufficient water volume, water quality complying with the NY5051 standard, and convenient water intake and drainage. The shrimp pond should be rectangular, broad and sunny, with a flat bottom, sandy soil or loam. During the shrimp's growth period, the pH value, ammonia nitrogen content, nitrite content, and dissolved oxygen of the shrimp pond water must all not exceed the standards.
3. Purchase high-quality shrimp fry. Before purchasing shrimp fry, investigate the seedling farm's production license, reputation, source of parent shrimp, the farming situation of shrimp fry sold over the years, and the disease and medication situation during seedling rearing. Shrimp fry must pass inspection and quarantine by the inspection and quarantine department before leaving the farm; do not bring in fry from epidemic areas, so as to prevent pathogens from being introduced.
4. Strengthen water quality management. During crayfish farming, appropriately add water and fertilize to maintain a certain fertility of the water quality, regulate the composition of algae in the water so that green algae or diatoms become the dominant population and form a certain quantity. Measure dissolved oxygen, ammonia nitrogen, nitrite, pH value and other indicators once every 7-10 d; if any indicator is unsuitable, relevant measures must be taken promptly. One month after stocking the shrimp fry, use good microbial preparations once every 10-15 d to remove harmful substances in the pond; after two months of farming, attention must be paid to improving the bottom substrate, such as using bottom substrate improvers and running aerators to increase oxygen.
5. Choose and feed good feed well. Choose palatable, nutritious feed varieties from manufacturers with large scale and stable quality, to meet the nutritional needs of each growth stage. Enhance the shrimp's immune function to resist pathogen invasion and sudden environmental changes. Feeding should adhere to many meals with small amounts, and supplement with live bait 1-2 times a week (small trash fish, snails, mussels, clam meat, etc.). Also regularly and periodically add immune polysaccharides, shrimp multivitamins, etc. to the feed to enhance disease resistance and anti-allergy ability.
6. Scientifically prevent and treat diseases. Disease prevention and control in crayfish farming should shift to prevention in many aspects, in management and health care. During farming, persist in morning and evening pond patrol inspections to observe whether shrimp diseases occur, and also understand the occurrence of shrimp diseases in and around the farming area, and take relevant measures promptly when problems are found. During the growth period, every 15-20 d, use bromochloro hydantoin once to splash and disinfect the whole pond; quicklime can also be used for disinfection, but the amount and frequency should not be too much.
Types of Freshwater Crayfish
1. Japanese swamp shrimp (Macrobrachium nipponense). Also commonly known as freshwater prawn, it belongs to the subclass Malacostraca, order Decapoda, suborder Natantia, family Palaemonidae, and has characteristics such as an omnivorous diet, fast growth, high reproductive capacity, and strong disease resistance.
2. Giant river prawn (Macrobrachium rosenbergii). The giant river prawn has different habitat habits at different growth stages. During the larval development stage, it must live in brackish water with a salinity of 8‰-22‰. Postlarvae and adult shrimp live in freshwater. The survival temperature is 15 to 35°C, and the suitable growth temperature is 22 to 32°C. Adult shrimp have no restriction on salinity, and can live in freshwater as well as in low-salinity brackish water. They also like to live in waters such as the lower reaches of rivers affected by tides and the lakes, canals, and paddy fields connected to them.
3. Red swamp crayfish (Procambarus clarkii). The red swamp crayfish resembles a shrimp but has a hard shell. The adult is about 5.6-11.9 cm long, dark red, with part of the shell nearly black, and a diagonal stripe on the back of the abdomen. Juvenile shrimp are uniformly gray, sometimes with black ripples. The claws are narrow and long. The middle of the shell is not separated by net-like gaps, and the shell has obvious granules. It can grow in salinity of 3‰ to 9‰; it can tolerate high temperatures of 40°C and low temperatures of -15°C. It has strong reproductive capacity.
4. Redclaw crayfish (Cherax quadricarinatus). Also known as Australian lobster, freshwater lobster, or redclaw crayfish. This shrimp can live in rivers, lakes, and ponds; it is benthic and crawls, and can also survive in brackish water. It is omnivorous, feeding on organic debris, aquatic plants, aquatic insects, small benthic animals, fermented cow dung, and artificial compound feed. The optimal water temperature is 22-32°C. The extreme water temperatures are 4°C and 37°C. When water quality deteriorates, it can crawl out of the water to save itself.
Construction of a Crayfish Farming Base
1. The site selection of a crayfish farming base must fully consider the surrounding environment, for example, whether the water source is abundant, the source of bait, and whether transportation and power supply are convenient, all of which need specific consideration. Among these, the investigation of water quality is very important, and the pH value of the water must be controlled at around 6-8.
2. For the disinfection work of a crayfish farming base, disinfection can generally be carried out with quicklime or bleaching powder. Simply crush the quicklime and evenly sprinkle it into the pond water, then on the second day use an iron rake to stir the pond bottom so that the lime and silt can be fully mixed. Of course, there are many other specific disinfection methods, and farmers can choose for themselves.
3. The construction of a crayfish farming base requires professional technical personnel. For a crayfish farming base, professional technical personnel are very important; for example, breeding pond preparation, parent shrimp selection, parent shrimp stocking, parent shrimp cultivation, water quality management, fertilization and hatching, shrimp fry cultivation, and so on all require scientific and reasonable technical support, so as to ensure the healthy growth of the crayfish.
Crayfish farming, whether in terms of base construction or crayfish farming techniques, involves certain skills and know-how. Although our country's aquaculture industry is developing relatively rapidly, it is still necessary to continuously research and develop new techniques and keep innovating in order to develop the aquaculture industry better and more broadly.