Key Technical Points for Natural Breeding of Yellow Catfish in Ponds

In recent years, artificial breeding techniques for yellow catfish have made some breakthroughs, and many places have attempted large-scale production of fry and fingerlings. However, due to the particular structure of the gonads of yellow catfish, both the fertilization rate in artificial breeding and the survival rate of fry and fingerlings are relatively low, so the price of fry and fingerlings is relatively high. Since 1999, Zhenglu Farm in Changzhou, Jiangsu, has explored and succeeded in natural breeding techniques for yellow catfish in ponds based on the breeding habits of yellow catfish in natural waters. The natural mating rate, egg fertilization rate and fry yield rate of yellow catfish are all relatively high, and the quality of the fry and fingerlings is good. For several consecutive years, it has achieved good economic returns. It is introduced as follows:

I. Preparation of the breeding pond

For the breeding pond, choose a pond that retains water and fertilizer, has a convenient water source, good water quality, and shallow and level bottom mud (15-20 cm), with an area of 1-2 mu being suitable. Make a water outlet in one corner of the pond, and dig a pond beside it for collecting fry. In November-December of the previous year, drain the pond water and expose it to the sun, dry it and freeze it to sterilize and kill insects. Around the Lantern Festival of the following year, plant grass as shelter and to regulate water quality. Generally, bamboo-node grass is better. First plant the grass in small flowerpots, then move the flowerpots into the pond with a spacing of 100 cm × 100 cm. If conditions permit, spread a layer of disinfected small stones in the shallow water around the pond, and at the same time add water to a depth of about 20 cm (filtered through 60-mesh silk bolting cloth), apply a small amount of organic fertilizer, and cultivate aquatic plants. Before stocking broodstock, clear the pond with quicklime or bleaching powder to disinfect it and kill wild miscellaneous fish and harmful organisms in the pond. After the toxicity disappears, add water to the fish pond to 60-80 cm. When adding water, the water inlet should be filtered with 60-mesh silk bolting cloth to prevent wild miscellaneous fish fry from entering.

II. Selection and stocking of broodstock

1. Source and selection of broodstock

Yellow catfish broodstock mainly comes from sexually mature individuals caught in rivers and lakes or from commercial fish from pond culture. The broodstock used for breeding should be selected from individuals with pure germplasm, large size, strong physique, no disease or injury, and that have reached sexual maturity. The female body weight should be above 75 g, and the male body weight above 100 g, with a female-to-male ratio of 3:2. Every December, put the selected broodstock into a 0.2-0.5 mu holding pond at a stocking density of 15,000 fish/mu.

2. Stocking and intensive conditioning of broodstock

At the end of February and the beginning of March, add filtered water to the breeding pond to 60-80 cm. At the same time, check the gonadal development of the broodstock, and put the better-developed broodstock into the breeding pond at a density of 80-100 fish/mu, with a female-to-male ratio of 3:2. From March onward, carry out intensive conditioning. During the conditioning period, feed self-made soft feed and ensure that the feed protein content is 40%-42%, while adding an appropriate amount of feed premix; feed twice a day, at 8-9 a.m. and 4-5 p.m., with 1/3 of the amount in the morning and 2/3 in the afternoon, and the feeding amount is 5%-8% of body weight. After entering April, also strengthen pre-spawning flowing water stimulation and pay attention to regulating water quality. Keep transparency at 30-35 cm and gradually add fresh water. By the time of breeding, control the water level at 1.2-1.3 m, with luxuriant aquatic plants. From mid-May to early June, the female fish have full and soft abdomens, obvious ovary outlines, and round, red and swollen genital pores, with relatively consistent maturity; the male fish have obvious genital papillae.

III. Breeding and fry rearing

1. Breeding

When the water temperature reaches 22-24 degrees C, the broodstock begin to chase, become excited and mate, and spawn on the spawning nests. Yellow catfish have the habit of guarding their young. After spawning, the broodstock guard the side of the spawning nests to prevent other fish from swallowing the eggs. After 6-8 days, when fry are found swimming level in the pond, begin collecting fry, that is, use a small water pump to pump water, with water entering on one side and exiting on the other, and collect the fry at the water outlet and put them into the fry rearing pond. At the same time, about one week before breeding, apply manure or green manure to the breeding pond to cultivate zooplankton for the fry to eat after the mouth opens. Generally, apply 300-400 kg of decomposed manure per mu, or 350 kg of green manure per mu.

2. Preparation of the rearing pond

Yellow catfish prefer low light, so the fry rearing pond is an indoor cement pond with an area of 300-400 sq m. Add water to a depth of 0.8-1.0 m. When adding water, the water inlet should be filtered with 60-mesh silk bolting cloth to prevent wild miscellaneous fish fry from entering. At the same time, build an outdoor biological bait culture pond of about 1 mu to cultivate rotifers, copepods and other bait organisms.

3. Fry and fingerling rearing

Put the fry collected from the breeding pond into the rearing pond at a density of 15,000 fish/sq m. Frequently introduce the cultivated bait organisms into the fry pond; at the same time, crush fresh low-value fish with a pulping machine, filter, and splash the filtrate into the fry pond. At the beginning, the feeding amount is 100%-150% of body weight, feeding once every 4 hours, and the feeding amount in the afternoon is about 60% of the whole day; after 2 days, change to feeding once every 6 hours. After 7-8 days of temporary rearing, the fry grow to 1.2 cm. At this time, they can be divided among ponds or sold. After another 7-8 days of rearing, such fry are grown into 1.8-2.0 cm fingerlings, that is, wuzai, and then large-size fingerling rearing is carried out.

The keys to the success or failure of natural breeding of yellow catfish in ponds are: the broodstock must be well selected; the clearing of the breeding pond and the fry rearing pond must be thorough; the aquatic plants used as spawning nests must be well planted; and the inlet water must be filtered through 40-60 mesh silk bolting cloth.