Detailed Explanation of the Key Techniques for Polyculture of Tilapia and Mandarin Fish

Tilapia is not tolerant of low temperatures. In late autumn and early winter, when the water temperature drops to 15°C, it can no longer continue to grow. In fact, a tilapia culture pond can only be used for half a year (May-October ). The mandarin fish is different: in winter it does not stop feeding completely and can still continue to grow, only with reduced feeding and a slower growth rate. Using the idle period of a tilapia culture pond to raise mandarin fish means that at this stage the fry are cheap and the bait fish are abundant, and the mandarin fish are raised until they are marketed in May of the following year, when the price is relatively high. Years of production practice have proven that the practical technique of rotating mandarin fish into tilapia ponds can effectively increase pond output, with the benefit per mu increasing by more than 3% compared with raising tilapia or mandarin fish alone. The specific techniques are as follows:

1. Stocking of mandarin fish fingerlings

When tilapia have been raised until August-September, most have reached marketable size (about 400 grams per fish) and can be caught and sold. By late October the pond is drained, and after routine pond clearing with quicklime, mandarin fish fingerlings are stocked 10 days later, with a size of 300-400 grams per fish and a stocking rate of 300 fish per mu of water surface. Before the fingerlings are put into the pond, they are disinfected with a salt mixture or similar.

2. Feeding of bait

In early November, when the mandarin fish are put into the pond, bait fish are also stocked at the same time, namely cheap silver carp, bighead carp and other fish of 25-50  grams each. Initially 150 kilograms are stocked per mu of water surface, and the feeding amount is gradually increased thereafter.

The feeding amount is: before the end of February, feed once every 7-10 days on clear days; from March, feed twice a week, with 15-20 kilograms per mu of water surface each time; in April, increase the feeding amount as appropriate according to the weather conditions. Ensure that the ratio of mandarin fish to bait fish is 1:5-10. If the bait fish density is too low, the mandarin fish will on the one hand not eat their fill, and on the other hand will consume too much energy chasing the bait fish, thereby affecting growth; if the bait fish density is too high, it easily causes oxygen deficiency and gasping at the surface. To ensure the same growth of the uneaten bait fish, an appropriate amount of rapeseed cake should also be fed.

3. Fertilization and water quality control

For raising market-size mandarin fish, the water body requires abundant dissolved oxygen and fresh water quality. In winter, add fresh water once every 15-20 days, each time to a depth of 10-15 cm; in spring, add fresh water once every 7-10 days, each time to a depth of 20-30 cm, ensuring that the dissolved oxygen in the water body remains above 4 mg per liter and the transparency remains above 40 cm.

4. Disease prevention and control

Mandarin fish has strong disease resistance, and basically no diseases occur during the culture process. Disinfecting the mandarin fish with a medicated bath before they enter the pond can prevent them from bringing disease into the pond. During the rearing process, bait fish should also be stocked consistently to ensure sufficient feed.