New Techniques for Healthy and High-Yield Pond Culture of Freshwater Shrimp

Freshwater shrimp, scientifically known as Macrobrachium nipponense (Japanese marsh shrimp), is a traditional aquaculture species in China. Because of its delicious taste and rich nutrition, it is deeply favored by the market and consumers. Compared with Macrobrachium rosenbergii (giant river prawn) and Penaeus vannamei (whiteleg shrimp), it requires less investment in fry and seed, has stable prices, and involves lower farming risks, so the freshwater shrimp aquaculture industry is relatively stable. However, as the scale of freshwater shrimp farming continues to expand and the degree of intensification increases, problems have emerged. The most prominent problem at present is severe inbreeding, germplasm degradation, and earlier sexual maturity, which brings problems to production:
First, sexually precocious freshwater shrimp grow slowly, with nutrition accumulating into gonad development, resulting in smaller commercial shrimp sizes and low market prices, directly affecting economic benefits;
Second, sexually precocious freshwater shrimp reproduce large numbers of postlarvae, rapidly increasing the density of freshwater shrimp in the pond. Postlarvae and adult shrimp compete for food, oxygen, and space, causing adult shrimp size to remain small, greatly reducing commercial prices, and also affecting farming yield, thus restricting the healthy development of the freshwater shrimp farming industry. How to improve the farming yield, commercial size, and economic benefits of freshwater shrimp is a issue of common concern to every shrimp farmer. Therefore, new farming models must be explored and new farming techniques found to achieve the goals of high quality, high yield, and high efficiency. Based on farming experience from previous years and combined with production practice, this article focuses on introducing new techniques for healthy and high-yield pond culture of freshwater shrimp for everyone's reference.
1. Good pond conditions must be created:
(1) Sufficient water sources are required, with fresh, pollution-free water quality that meets national fishery water standards. Dissolved oxygen should be greater than 5 mg/l, and dissolved oxygen at the pond bottom should be greater than 3 mg/l, with a pH of 7.5-8. The area should be 2-5 mu, with a water depth of 1.2-1.8 m; the pond bottom should be flat, with a slope of 1:2-2.5; each pond needs to be equipped with 1-2 aerators of 1-1.5 kW; the water inlet should be filtered with an 80-mesh mesh bag to prevent wild fish and fertilized eggs from entering the shrimp pond.
(2) Pond clearing and disinfection: 7-10 days before stocking shrimp fry, apply 75-100 kg/mu of quicklime broadcast over the entire pond for disinfection to kill pathogens and harmful organisms.
(3) Add water and fertilize. 2-3 days after lime disinfection, add water to 50-60 cm, and apply 150-200 kg/mu of fermented organic fertilizer to cultivate natural food organisms.
(4) Set up aquatic plants and shelters. Plant grass immediately after adding water to the shrimp pond. The aquatic plants should be mainly Hydrilla verticillata (water thyme), supplemented with a small amount of Potamogeton crispus (curly-leaf pondweed), with a spacing of 1-2 m. Plant Potamogeton crispus in deep water and Vallisneria natans (tape grass) in shallow water, with coverage accounting for about 30% of the water surface. The functions of aquatic plants: they provide perching, molting, and hiding places for freshwater shrimp; photosynthesis can increase dissolved oxygen in the water; they purify water quality and prevent water quality deterioration. Production practice from various regions shows that ponds with more aquatic plants have freshwater shrimp that carry eggs later and are larger in size. In addition, tea branches, bamboo tips, etc. can be placed in the shallow water areas of the shrimp pond. If conditions permit, netting can also be laid to implement three-dimensional culture, increasing perching places for freshwater shrimp, further improving water body utilization, and effectively increasing yield and improving commercial shrimp size.
2. Purchase high-quality shrimp fry and stock reasonably:
(1) Shrimp fry should be purchased from freshwater shrimp original (improved) seed farms. Do not breed your own for many years to save costs. Choose shrimp fry bred from egg-carrying shrimp from other locations or original (improved) seed farms. As long as the fry density in the nursery pond is moderate, generally controlled within 800,000-1,000,000 tails/mu, the fry produced will be relatively uniform in size. If farmed shrimp are chosen as parents for breeding fry, due to inbreeding, harmful genes in freshwater shrimp continuously become homozygous, making seed quality increasingly poor, sexual maturity increasingly early, and commercial shrimp size increasingly small.
(2) Appropriately delay the stocking time. Shrimp fry stocked in May and June, after 2-3 months of rearing, have mostly reached sexual maturity, and in August and September will produce large numbers of first-generation offspring. If stocking is delayed to mid-to-late July, the sudden change in the living environment of freshwater shrimp can control the autumn breeding phenomenon to a certain extent.
(3) Adjust stocking density and implement rotational harvesting and sparse culture. The timing of sexual maturity in freshwater shrimp is closely related to stocking density. The greater the stocking density, the earlier the sexual maturity. Reasonable density can not only ensure higher yields of freshwater shrimp but also delay egg-carrying in the vast majority of freshwater shrimp, accelerating growth to reach larger sizes. The specific stocking density should be determined according to the farming model: for pond monoculture of freshwater shrimp, stock 60,000-80,000 fry of 1.5-2.0 cm per mu; for mixed culture with conventional fish, stocking 15,000-20,000 fry per mu is sufficient. For spring stocking of shrimp seed, the density should not be too high; generally, stock 8-10 kg per mu of shrimp seed at 1,200-1,600 individuals/kg to ensure they are grown to market size in May-June.
In addition, after September, measures of rotational harvesting and sparse culture, harvesting large ones and retaining small ones, should be adopted. Timely harvest and sell shrimp that have reached commercial size to reduce the shrimp load in the pond and promote freshwater shrimp growth.
3. Reasonable feed feeding: Freshwater shrimp feed should be high quality and fresh, with palatable particle sizes. During the juvenile shrimp stage, the crude protein content should reach 35-40%. In the middle and late stages (above 4 cm), feed adult shrimp feed with a crude protein content of 30-32%. Feeding should follow the "four fixed" principle, and specific adjustments should be made flexibly according to weather, water temperature, water quality changes, and feeding conditions.
4. Strengthen water quality management and maintain good water quality. Freshwater shrimp cannot tolerate low oxygen; their oxygen consumption rate and asphyxiation point are both higher than those of major freshwater farmed fish. When there is insufficient oxygen in a fish pond, freshwater shrimp always surface for air and die before the fish. Therefore, regulating water quality is the key to the success or failure of freshwater shrimp farming and the level of yield. Shrimp farming water quality must meet the requirements of "fertile, lively, tender, and refreshing." The main measures are as follows:
(1) Mechanical aeration. Because the stocking quantity of freshwater shrimp is relatively large and density is high, sufficient dissolved oxygen must be ensured in the shrimp pond. During July, August, and September, aerators should be run more from 16:00 each afternoon to 7:00 the next morning. On stuffy or rainy days, aerators should also be appropriately run during the day. Especially when stocking freshwater shrimp fry in autumn, which coincides with the high-temperature season, netting and stocking fry are generally carried out in the morning at lower temperatures, but this is precisely the time when the pond water body is short of oxygen. If aeration measures are not taken in advance for the fry pond, it is easy to cause fry to die from oxygen deficiency.
(2) Frequently add fresh water or apply microbial preparations. Frequently adding fresh water is the most effective measure to improve the shrimp water environment and maintain good water quality. In places with convenient water sources and good water quality, adding fresh water can increase dissolved oxygen, nutrients, and trace elements, dilute metabolic products and toxic substance concentrations, and prevent pond water from becoming aged. In shrimp ponds lacking water sources or where water addition is inconvenient, beneficial microbial preparations such as photosynthetic bacteria, EM original liquid, and Bacillus should be used to improve and regulate water quality.
(3) Apply supplementary fertilizer at the appropriate time to cultivate plankton, maintaining the water color as the ideal yellow-green or brown, with transparency controlled at 25-30 cm. For supplementary fertilization, decomposed organic fertilizer and chemical fertilizers such as urea and superphosphate are generally suitable.
(4) Regularly broadcast quicklime. Generally, every 15-20 days, broadcast 15 g/cubic m of lime water over the entire pond, which regulates pH while also serving the functions of sterilization and calcium supplementation.
5. Stock fish species at the appropriate time to control excessive reproduction of freshwater shrimp:
In the process of freshwater shrimp farming, in order to maintain a reasonable farming density in the shrimp pond and improve the commercial rate of freshwater shrimp, when postlarvae have reproduced to a certain number, some fish species can be appropriately stocked. This not only maintains the biological diversity of the water body but also controls excessive reproduction of freshwater shrimp in the pond. The timing for stocking fish species should be controlled at the end of August and the beginning of September. The main stocked species are silver carp and bighead carp, Xiangyun crucian carp, bream, yellow catfish, and other fish species. The quantity should not be too much, generally about 100 fish per mu. Let the fish species feed on the large amount of plankton and the pre-metamorphic nauplius larvae of freshwater shrimp in the pond, thereby controlling the number of freshwater shrimp fry.
6. Several methods for controlling sexual precocity and density of freshwater shrimp:
(1) Improve the stocking model: Many farmers mainly stock egg-carrying shrimp, implementing self-reproduction, self-nursing, and self-culture. This model is an extensive shrimp farming method. Although the seed cost is low and it is convenient and practical, it is difficult to control density, the size of market shrimp is uneven, and both yield and efficiency are low. Therefore, to improve yield and efficiency, technical measures must be adopted such as changing extensive culture to intensive culture, changing the stocking of egg-carrying shrimp to stocking high-quality shrimp fry, and changing one crop of shrimp to two crops of shrimp.
(2) In early September, when nauplius larvae appear in the shrimp pond, measures such as increasing water exchange or applying 20 kg/mu of quicklime after slaking and broadcasting over the entire pond can rapidly raise the pH value, causing postlarvae and un-metamorphosed nauplius larvae to die because they cannot tolerate the sudden change in water quality factors.
7. Strengthen shrimp disease prevention and control: Adhere to the principle of "prevention first, health management." In addition to pond clearing and disinfection, selecting high-quality shrimp fry, reasonable stocking, and feeding, preventive work includes regularly applying quicklime, dibromohydantoin, super iodine quaternary ammonium salt, etc. for water body disinfection. Freshwater shrimp have far fewer diseases than Penaeus vannamei, river crabs, and fish. The main diseases include black gill disease, red body disease, and soft shell disease. Targeted medication should be used according to different diseases, and timely treatment should be provided.