Detailed Explanation of Key Techniques for Mandarin Fish Pond Aquaculture

1. Living habits of mandarin fish: a bottom-dwelling fish, living in still water and rivers, lakes and reservoirs with some flowing water, especially in shallow lakes with abundant aquatic plants. During the day it generally lurks at the bottom, and at night it moves around foraging, has the habit of digging burrows and making nests, does not like living in groups, and its suitable living water temperature is 15-32°C; when the water temperature is below 7°C it is not very active and does not feed much. In pond aquaculture, mandarin fish often lie at the bottom, hidden in relatively shallow burrows.

2. Food and feeding habits of mandarin fish: a carnivorous, ferocious fish; after hatching, as soon as it starts feeding it eats the fry of other fish, prefers live bait, and when hungry it cannibalizes its own kind. At the fry stage it can swallow fry of other farmed fish species equivalent to 70-80% of its own length. The size of the bait fish it eats depends only on what its mouth gape can swallow, regardless of the length of the fish body. Under artificial breeding conditions, when bait types are diverse and abundant, it often chooses fish that are slender in body shape, soft in fin rays and smaller in individual size as food. The maximum length of bait fish that an adult mandarin fish can easily swallow is 60% of its own length, but those at 26-36% have better palatability.

3. Growth rate of mandarin fish: under artificial breeding conditions, with palatable and sufficient bait, growth is relatively fast. A 1-winter-old mandarin fish raised in a cage has an average body length of 31.68 cm, equivalent to the body length of a 3-winter-old mandarin fish in natural waters. Mandarin fish before age 2 grow faster than older fish, and age-1 fish grow faster than age-2 fish. In winter, mandarin fish do not completely stop feeding and continue to grow, but feeding intensity and growth rate slow down.

4. Pond area for farming mandarin fish: an area of 4-6 mu is preferable, with a minimum of no less than 1 mu and a maximum of no more than 10 mu. If the pond area is too small, water quality changes quickly and is difficult to control; if the pond area is too large, the bait fish are relatively dispersed, which is not conducive to feeding by mandarin fish. The pond should be sheltered from the wind and facing the sun, oriented east-west, with a length-to-width ratio of 3:2, a flat bottom, sandy loam soil, and ideally a newly dug pond with little or no silt, with a water depth of about 1.8-2.5 m, sufficient water source, fresh water quality, and convenient water intake and drainage, preferably using river and lake/reservoir water, and ideally with slight water flow. Before mandarin fish fry and fingerlings are stocked into the pond, the pond must be thoroughly cleared and disinfected, and aerators must be installed.

5. Production of bait fish in the main pond: 15 days before stocking mandarin fish, put 600,000-800,000 bait fish fry per mu into the disinfected pond after its toxicity has dissipated, and cultivate the bait fish in the pond to 1.2-2.0 cm each.

6. Timing of stocking mandarin fish fry into the pond: when the bait fish in the pond have been cultivated to 1.2-2.0 cm each, this is exactly the time to provide sufficient and palatable early-stage bait fish after mandarin fish are stocked. Place an appropriate amount of alligator weed and water hyacinth around the pond for mandarin fish to rest on. Afterwards, control the body length of the bait fish at 1/4-1/3 of the body length of the mandarin fish.

7. Stocking density and size of mandarin fish: stock 1,000-1,200 summer fry of mandarin fish per mu at 3-5 cm each.

8. Supporting production of bait fish: under normal circumstances, the bait fish in the main mandarin fish pond can supply mandarin fish feeding for 1 month. After 1 month of rearing, mandarin fish body length can generally reach 11-14 cm. In the supporting bait fish ponds (3-4 times the size of the mandarin fish farming pond), according to the requirement of a mandarin fish bait coefficient of 1:4-5, use the advantage of multiple ponds, adopt farming methods of rearing at different densities, harvesting in batches, and gradually thinning out, to raise bait fish, and control the body length of the bait fish at about 50-60% of the body length of mandarin fish at the same period, ensuring that bait fish and mandarin fish grow synchronously so that mandarin fish can feed on them.

9. Optimum growth water temperature for mandarin fish: the growth water temperature for mandarin fish is 18-30°C, with the optimum water temperature being 23-28°C. Within this range, as the water temperature rises, its feeding amount increases and its growth rate accelerates.

10. Feeding of bait fish: during the farming period, the method of feeding bait fish at intervals can be adopted according to changes in water temperature. In the early and late stages, feed once every 7-10 days; in the middle stage (the high-temperature period of July, August and September), feed once every 5-7 days. Bait fish should be fed in an appropriate amount. If the density is too low, mandarin fish will consume too much energy chasing bait fish, which is detrimental to growth; if too dense, the total oxygen consumption will increase, causing mandarin fish to surface for oxygen and adversely affecting their growth.

11. Feeding amount of bait fish: each feeding amount is 8-10% of the total amount of mandarin fish, maintaining a ratio of mandarin fish to bait fish of 1:5-10. After bait fish are put into the mandarin fish pond, they still have a period of growth, so a small amount of concentrated feed may be fed as appropriate.

12. Water quality management: mandarin fish prefer fresh water quality and have relatively poor tolerance to low oxygen, so strengthening water quality management is very important. Before stocking mandarin fish fry, first drain half of the pond water, then fill in new water to make the pond water clear, and then stock the mandarin fish fry. Mandarin fish are very sensitive to acidic water quality. From June to October, every 15-20 days or so, use 20-25 jin of quicklime per mu, slaked in water and splashed over the whole pond, to maintain a pH value of 7-8, which is beneficial to the feeding and growth of mandarin fish.

13. Adding and changing water in stages: in the early stage of stocking, add new water once every 7-10 days, with each addition amounting to 10-20% of the pond water volume, until early to mid-July, gradually deepen the pond water to more than 1.5 m. From mid-July to September, as the water temperature rises, generally try to change the water once every 2 weeks, keeping water transparency at 30-40 cm. When it is less than 30 cm, replace 1/4-1/3 of the pond water. It is even better if circulating water conditions can be maintained regularly, so that the dissolved oxygen content in the water is always above 4 mg/L.