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Cultivating fish species
Fish species are typically categorized into fry and fingerlings based on their developmental stage. Fry refers to newly hatched fish from eggs, while fingerlings are the juvenile stage that follows after several growth phases. The transition from fry to fingerling generally involves three distinct stages: the summer flower stage, the first-year fingerling stage, and the second-instar fingerling stage.
The first stage, known as the summer flower phase, lasts about 20 to 30 days. During this time, fry are small, fragile, and have limited mobility, making them highly sensitive to environmental changes. Therefore, careful management is essential during this period. Fish ponds should be chosen with good irrigation systems, fertile soil, and strong water retention. The pond area should not be too large—ideally between 1 to 2 mu (about 0.67 to 1.33 acres). Before introducing fry, the pond must be cleaned and disinfected using lime or bleach. The water depth should be maintained at 0.5 to 1 meter.
Feeding is crucial during this early phase. Fry primarily feed on zooplankton, but they can also be supplemented with soy milk. To support natural food sources, the pond should be fertilized with organic waste, green manure, or chemical fertilizers. It’s common to apply 50 to 100 kg of green manure per acre before the fry arrive. If a quicker response is needed, nitrogen-based fertilizers can be used. Water quality should be monitored regularly, and top-dressing should be adjusted according to the clarity of the water, weather conditions, and fry development. A tea-brown or yellowish-green water color is ideal for fry growth.
Soy milk should be prepared by boiling and grinding soybeans, then evenly distributed in the pond. About 2.5 kg of soybeans per day is sufficient, spread in small portions. For species like carp and grass carp, it's important to distribute the milk along the edges of the pond to ensure even feeding.
In the second stage, the fish grow to about 3.3 cm and are referred to as summer flowers. Although they are more developed, they are still vulnerable and need further cultivation. This leads to the first-year fingerling stage, where fish grow to 12–15 cm and are ready for larger-scale farming. During this phase, different fish species should be raised separately or mixed depending on local practices. Polyculture is often beneficial, with some species dominating the pond. For example, squid and silver carp may make up 70–80% of the population, while others like grass carp and herring take up the remaining 20–30%. Fertilization is key here to maintain plankton levels, and feeding should be done regularly with soy milk, bran, or cereal flour.
Feeding techniques include setting up feeding stations made of bamboo or other materials to ensure fish can access bait efficiently. The amount of food should be adjusted based on fish size and consumption rate to avoid overfeeding or underfeeding. Proper feeding helps maintain healthy growth and reduces waste.
By the second year, the fish reach the second-instar stage, growing to around 150–250 grams. At this point, survival rates are high, and growth is rapid. Careful management, including proper stocking density and timely pond separation, ensures optimal development. These fingerlings are then ready for final-stage production, contributing to higher yields and better market value.