Freshwater fish farming is a widely practiced activity, with numerous methods tailored to local water conditions and species. Across the country, more than a dozen distinct aquaculture models have been developed, each suited to specific environmental and biological factors. While it's impossible to detail every model here, this article will focus on three commonly used techniques: pond fertilization, high-density pond culture, and semi-intensive reservoir farming.
**1. Pond Fish Fertilization**
In certain regions of Central China, such as Sichuan and Chongqing, many ponds still follow traditional breeding practices, primarily focusing on eel and loach cultivation. This method relies heavily on natural ecological cycles to reduce costs and improve productivity.
**Cultivation Conditions**:
Ponds should be between 5 to 20 acres in size, with a depth of 1.5 to 3 meters and a bottom mud layer of 10 to 20 cm. They must be located near a reliable water source for easy irrigation and drainage.
**Culture Characteristics**:
This system promotes material cycling among organisms, enhancing the productivity of the water body. After applying fish fertilizer, plankton populations increase, boosting primary production. Phytoplankton also helps raise dissolved oxygen levels, accelerate organic matter decomposition, and provide ample food for fish, thus improving growth rates and overall pond efficiency.
**Cultivated Species**:
Mainly whitefish (such as silver carp and bighead carp), along with some mid- and bottom-dwelling species like grass carp and crucian carp.
**Stocking Plan**:
The typical stocking ratio is about 70–80% silver carp, 5–10% bighead carp, 10% grass carp, and 5% other species. Seedlings are usually stocked in autumn at sizes of 11.6–13.2 cm. A density of 200–300 fish per acre is common, with refills done in spring if needed. The total number per mu (approximately 0.067 hectares) ranges from 700 to 800, with an average weight of 17–18 kg.
**Preparation Before Stocking**:
Seven to ten days before stocking, the pond should be cleaned using lime or chemical treatments during sunny afternoons.
**Feeding Management**:
1. **Base Fertilization**: From mid-April to mid-May, apply "Tianchen Fish Fertilizer" or traditional fertilizers in stages. At this time, fertilization should be 2–3 times the normal rate, aiming for good water quality. Slough or newly dug ponds require more frequent fertilization.
2. **Top Dressing**: Starting in June, continue fertilizing to maintain water quality. Traditional fertilizers are not recommended due to rising temperatures; instead, use "Tianchen Fish Manure." In June, apply 2–3 kg/mu 4–5 times per month, increasing to 5–7 times in July and August. Reduce applications after September.
3. **Water Quality Control**: After May, regularly add fresh water. Every 20–30 days, apply quicklime to keep the water clean and prevent diseases. Maintain pH between 7.3 and 7.8.
**Harvesting**:
After one year of farming, the average weight of silver carp can reach 0.75–1.0 kg, while bighead carp can reach 0.75–1.2 kg. Harvest at optimal times for balanced yield and market value.
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**2. High-Density Pond Culture (Mainly Concentrated Feed)**
With the widespread use of compound feed, many farmers have transitioned from feeding whitefish to more intensive systems involving grass carp, silver carp, and other species. However, fertilization remains important, especially for maintaining natural food sources.
**Cultivation Conditions**:
Ponds should be between 5 and 30 mu, with a depth of 1.5 to 3 meters and good access to water.
**Culture Characteristics**:
High-quality exogenous nutrients, such as compound feeds, are used to ensure adequate nutrition for fish. Feeding residues and fish feces act as natural fertilizers, promoting the growth of plankton and improving overall productivity.
**Cultivated Species**:
Silver carp, bighead carp, grass carp, herring, tilapia, and stingrays are commonly raised.
**Stocking Density**:
Typical stocking rates include 300 silver carp/acre, 50 bighead carp/acre, 150 grass carp/mu, 90 tilapia/acre, 400 crucian carp/acre, and 250 stingrays/acre.
**Preparation Before Stocking**:
Seven to ten days prior, clean the pond using lime or chemicals on sunny days. Disinfect fish species before stocking.
**Fertilization and Management**:
1. Monitor the behavior of cultured species.
2. Follow the "three observations and four determinations" principle: observe weather, water color, and fish activity; determine time, location, quantity, and quality of feeding.
3. Maintain water quality by keeping it rich, clear, and cool. If transparency exceeds 35 cm, apply "Tianchen Fish Fertilizer" at 2–3 kg/mu to regulate water quality and prevent disease.
4. Use aerators and disinfect the entire pond to reduce the risk of disease.
**Harvesting**:
After one year, yields typically reach 300 kg/mu for silver carp, 500 kg/mu for bighead carp, 200 kg/mu for grass carp, 180 kg/mu for herring, 200 kg/mu for crucian carp, 130 kg/mu for carp, and 30 kg/mu for stingrays, totaling around 1100–1200 kg/mu.
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**3. Semi-Intensive Reservoir Farming**
As market prices rise, small and medium-sized reservoirs are increasingly being converted to semi-intensive systems that combine natural fertilization with artificial feeding. These systems are particularly effective in open, well-lit reservoirs with limited water exchange.
**Cultivation Conditions**:
Reservoirs should be well-watered, with an open surface and strong sunlight. Water depth should not be too deep, and there should be facilities for fish control.
**Culture Characteristics**:
Large areas of tens to thousands of mu are easily managed. The water quality is generally good, and the environment supports robust fish growth.
**Cultivated Species**:
Grass carp, silver carp, and bighead carp are dominant, with some high-value species also raised.
**Stocking Plan**:
Generally, 80–85% silver carp, 15–20% bighead carp, and an appropriate amount of grass carp. Seedlings should be larger, typically 3–4 cm or more. In eutrophic or fully fertilized reservoirs, 150–250 fish/mu may be stocked, while in ordinary reservoirs, 100–150 fish/mu is typical. All fish should be healthy, disease-free, and uniformly sized.
**Preparation Before Stocking**:
Fish must be disinfected before stocking. Apply large amounts of agricultural fertilizer or "Tianchen Fishery Fertilizer" to the reservoir to promote initial productivity.
**Fertilization Management**:
1. Apply base fertilizer before and after stocking, combining traditional and modern fertilizers.
2. For high-density stocks, maintain water clarity at 30–40 cm.
3. When water temperature is 20°C, plankton peaks 4–5 days after application of "Tianchen Fishery Fertilizer," lasting 7–8 days. Reapply every 13–15 days. At 25°C, plankton recovers in 5–6 days, so apply every 10 days. From June to August, apply every 3–4 days, with reapplication every 6–7 days. Aim for 4–7 applications per month in summer, reducing after September.
4. Apply fertilizer in bays or upwind areas, preferably at noon on sunny days.
5. Keep pH between 7.3 and 7.8. If acidic, apply lime two days before fertilizing.
This detailed approach ensures sustainable and productive freshwater fish farming, adapting to both traditional and modern practices.
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