Key Technical Points and Daily Management Knowledge for Fish Farming in Reservoirs Explained

Now many people are starting fish farming in rural areas, and many people are building a reservoir in rural areas, but fish farming in reservoirs also involves many particular points. Below, let's take a look at the related knowledge together with the editor, hoping it can help new farming friends.

Reservoir Fish Farming Knowledge

1. Species to stock: The purpose of applying chemical fertilizer is to fertilize the water and breed plankton, so reservoirs mainly stock filter-feeding fish such as bighead carp and silver carp, with an appropriate mix of grass carp, bream, and black carp.  

2. Stocking ratio: filter-feeding fish account for 80%-90%, and other fish account for 10%-20%.  

3. Stocking time and size: large-size fingerlings of 13.20 cm or more, preferably 0.05-0.10 kg per fish, are stocked into the reservoir in batches in autumn, winter, and spring. Summer fry are best at 6.60 cm or more, preferably stocked into the reservoir in late May to early July, in 2-3 batches.  

4. The number of fingerlings to stock is determined by factors such as reservoir conditions, technology, and funds. Generally, 500-600 large-size fingerlings of 13.20 cm or more are stocked per mu, with 500-800 summer fry of 6.60 cm or more stocked as a supplementary species per mu.  

How to Fertilize in Reservoir Fish Farming  

1. Fertilization time: chemical fertilizer can be applied once the water temperature reaches 18 degrees Celsius. The fertilization period is generally from mid-April to late October.  

2. Types of chemical fertilizer: the chemical fertilizers tried in reservoirs include nitrogen fertilizer and phosphorus fertilizer.  

3. Nitrogen-phosphorus fertilizer ratio: considering factors such as fertilizer efficiency and fertilizer price, generally ammonium chloride and superphosphate, or ammonium bicarbonate and superphosphate, are applied.  

4. Fertilization amount: according to experiments, when the nitrogen content in reservoir water reaches 2 mg/L, the plankton biomass reaches more than 20 mg/L, meeting high-yield requirements.  

5. Water color and transparency: after fertilization, when the water is fertile, the water color is oily green or dark green. Transparency is 15-25 cm.  

Precautions for Fertilization  

1. Grasp the fertilization order well: the order for applying chemical fertilizer is to apply phosphorus fertilizer first and then nitrogen fertilizer; this cannot be reversed. Nitrogen and phosphorus fertilizers must not be mixed together and applied, otherwise fertilizer efficiency will be lost.  

2. Choose good weather: fertilization on sunny days is best.  

3. Fertilization should be done in small amounts many times: when the water is fertile, plankton is abundant, and nutrient elements should be supplemented in time. This not only allows the fertilizer applied into the water to be quickly absorbed and utilized, improving fertilizer efficiency, but also helps plankton reproduce and grow rapidly, providing abundant and stable food for fish production. By all means avoid fertilizing again only when the water is relatively lean, otherwise a large amount of supplementary fertilizer is needed before the water becomes fertile, and production time is delayed, the chemical fertilizer coefficient increases, costs rise, and benefits are affected.  

4. Have a good application method: generally apply in the upwind shallow-water area of the reservoir. Fully dissolve nitrogen and potassium fertilizers in water and sprinkle evenly, with the boat moving in an S shape.  

5. Appropriately apply quicklime to regulate water quality: long-term application of chemical fertilizer makes water quality acidic. From May to August, quicklime should be applied once each month, 15-20 kg per mu each time, so that the calcium content of the reservoir water reaches more than 100 mg/L (preferably 120-180 mg/L). Applying quicklime is also to meet the calcium requirements for the bone growth of plankton and fish.  

Four tips for fish farming in small reservoirs: small reservoirs are generally between several dozen mu (1 mu = 1/15 hectare, the same below) and several hundred mu, with a water depth of about 10 m, and they are rich in dissolved oxygen and feed.  

Management Techniques for Fish Farming

1. Reasonable matching and timely stocking: reservoirs have more predators and a poorer feed base than ponds, and small fingerlings have a poor ability to escape predators and a relatively low feeding ability. Therefore, if stocked fingerlings are too small, the survival rate will be relatively low. Generally, large-size fingerlings of 13 cm or more should be stocked to obtain a relatively high recapture rate and marketable rate. In terms of species matching, when using chemical fertilizer for fish farming, silver carp and bighead carp should be the main species, and their output can account for more than 90% of total fish output; the stocking ratio of silver carp to bighead carp is 4:1. Grass carp, common carp, and crucian carp fingerlings should make up 20%-30%.  

The stocking density in reservoirs should be determined according to the amount of feed organisms in the water and the amount of fertilizer applied. Generally, 200-500 fish are stocked per mu, and they can reach marketable size in the same year. For stocking fingerlings in reservoirs, autumn and winter are best, which allows the fingerlings to adapt in advance to the living environment of large water surfaces. At the same time, because the activity ability of predatory fish weakens in winter and their food intake decreases, this helps increase the survival rate of fingerlings. The release site should be chosen in an upstream area sheltered from the wind and facing the sun, and released at separate points. By all means do not release them near the dam or drainage sluice.  

2. Grasp a reasonable fertilization amount: the application amount should be determined according to water body conditions and different seasons, and it is best if after application the transparency is 25-30 cm and the water color is yellowish brown or brownish green. From April to May, organic fertilizer should be the main type, applying 250-300 kg of organic fertilizer per mu, while also applying inorganic fertilizer; from June to August, inorganic fertilizer should be the main type, with nitrogen fertilizer and phosphorus fertilizer applied in a mixed ratio of 2:1, applying 1.5-2.5 kg/mu of nitrogen fertilizer and 2.5-5 kg/mu of phosphorus fertilizer, once every 10-15 days.  

Nitrogen fertilizer is mainly urea or ammonium bicarbonate, and phosphorus fertilizer is mainly superphosphate. Apply phosphorus fertilizer first, then nitrogen fertilizer; this cannot be reversed, so as to avoid causing fish deaths. Fertilization should be chosen on sunny days and applied by the sprinkling method in the shallow-water area of the upper and middle reaches of the reservoir, avoiding places where aquatic grass grows densely. Do not apply it in the downstream deep-water area or near the dam.  

3. Fish disease prevention is more important than treatment: fingerlings must be disinfected before stocking; ordinarily, quicklime or bleaching powder is sprinkled over the whole reservoir, water quality is regulated at fixed times during the high-temperature season, and fish diseases are treated promptly when found. Commonly occurring diseases include branchial necrosis and print disease, and there are parasitic infections by anchor worms and fish lice. Bacterial diseases can be treated by sprinkling bleaching powder at 1 g/cubic meter over the whole reservoir, and parasitic diseases can be treated by sprinkling 90% crystallized trichlorfon at 0.3-0.5 g/cubic meter over the whole reservoir.  

4. Daily management must be in place: frequently apply quicklime to raise the pH and hardness of the water area, increase calcium salts, promote material circulation in the water area, improve water quality, and help fish growth and inhibit the occurrence of fish diseases. Generally, apply 15-20 kg of quicklime per mu each time, once a month. Before stocking fingerlings, use combined fishing gear to remove wild fish or use drugs to kill wild and miscellaneous fish.  

During the farming period, use surrounding nets and trawl nets at fixed times to lure and catch wild and miscellaneous fish, increasing the survival rate of stocked fingerlings. For intensive fish farming with fertilization in small reservoirs, there must be aeration equipment, transport equipment, irrigation and drainage machinery, escape-prevention facilities, and fishing nets. In addition, the reservoir must have someone on duty, paying attention to understanding situations such as flood control and irrigation, frequently checking fish-blocking facilities, promptly salvaging floating objects, ensuring the drainage outlet is unobstructed, and preventing fish from escaping. Frequently observe whether the water quality is good or bad and check the growth status of fish so as to fertilize reasonably.

With the continuous development of China's aquaculture industry, fish farming is one of the better-developed activities in China, but farmers should not blindly follow the trend. Before farming, they should first understand market conditions and demand, so as to avoid unnecessary losses caused by blindness.