Methods for Achieving High Yield in Intensive Culture of Yellow Catfish

1. Pond conditions

An intensive high-yield fish pond requires a good water source, convenient drainage and irrigation, an area of 1,334—3,335 sq m (2—5 mu), a water depth of 1.5—2 m, fresh water quality, abundant dissolved oxygen, and little sludge at the pond bottom. Still-water ponds must be equipped with aerators.

Drain the pond water 7 days before stocking, and use 100 kg of quicklime per 667 sq m (1 mu) to disinfect the pond. On the 3rd day, fill with fresh water and use “901 Yuchongjing” to kill enemies such as water centipedes and tadpoles, improving the survival rate of yellow catfish fry and fingerlings.

2. Fry stocking

Artificially bred yellow catfish fry in the Poyang Lake area can reach 1.5 cm by early June. It is best to temporarily rear them in cement ponds or small earthen ponds for 10 days until they reach the summer-fry size of about 3 cm before stocking into the pond. During temporary rearing, mainly feed red worms and minced fish meat, and later mix in powdered compound feed. The stocking density depends on pond conditions and the degree of feed security; generally, the stocking density can reach 5,000—8,000 fry per 667 sq m. Under normal conditions, after 120—150 days of rearing, the individual weight can reach the commercial size of 100—150 g, with a yield of 500—800 kg per 667 sq m of water surface. Yellow catfish are docile and weak at competing for food, so it is not advisable to polyculture them with other food-eating fish. To regulate water quality and reasonably utilize natural food organisms, it is necessary to polyculture large-sized (over 100 g per fish) silver carp and bighead carp fingerlings at a density of about 200 fish per 667 sq m; the polycultured fish yield can reach 150 kg.

Before stocking, fry must be disinfected by bathing in a 3.5% salt solution or 60 mg/L formaldehyde for 5 minutes to kill body surface pathogens and parasites. Because of the high temperature, it is best to carry this out in a net cage wrapped with colored cloth.

3. Feed feeding

Yellow catfish is an omnivorous fish with a tendency toward animal food. The prerequisite for intensive high yield is feeding large amounts of high-quality feed and achieving scientific feeding. Set up 2—4 feeding platforms and carry out feeding training so that the fish school gathers to compete for food at a fixed time and fixed location. Before the individual weight reaches 20 g, use fish meat mixed with powdered compound feed, add water, and knead it into balls for feeding; when the individual weight is 20—50 g, feed compound feed with a particle size of 1.5 mm and a crude protein content of 35%—40% (or crushed fry feed); when the individual weight is above 50 g, switch to compound feed with a particle size of 2.5 mm and a crude protein content of about 30%.

During the culture period, strictly follow the “four fixeds” in feeding: First, fixed location. Feed should be placed on or near the feeding platforms; do not feed randomly throughout the pond, and do not change location with the movement of the fish school. Second, fixed time. Every day from 9—10 a.m., feed 1/3 of the daily ration, and from 4—5 p.m., feed 2/3, each feeding lasting 30 minutes, and feed according to the rhythm of “slow, fast, slow” to avoid nutrient dissolution and loss. Third, fixed quantity. The daily ration should be adjusted in good time according to changes in water temperature and fish growth; the daily feeding rate is 3%—8%, generally taking the point at which most fish are full and leave the feeding platform 1 hour after feeding as the standard. Fourth, fixed quality. Ensure the feed is fresh and not spoiled; on the premise of a reasonable price, choose high-quality feed with high protein content, balanced nutrition, good palatability, and good stability. Under normal conditions, the feed conversion ratio is about 2.5. The lakeside areas are rich in wild trash fish resources, so ice-fresh fish meat can be mixed in for feeding to reduce feeding costs.

4. Water quality management

Yellow catfish prefer clear water, requiring pond water dissolved oxygen to reach 5 mg/L, and not lower than 3 mg/L for most of the day. Because intensive ponds have high density and are heavily fed with high-protein feed, excrement and residues easily deteriorate water quality, leading to oxygen deficiency and floating at the surface, or even pond-wide fish kills. During the culture period, on the one hand, regularly add fresh water and replace old water to ensure the water quality is fresh, lively, tender, and crisp; on the other hand, reasonably use aerators and make full use of their functions of stirring water, aeration, and oxygen enrichment to avoid eutrophication of pond water leading to low dissolved oxygen syndrome.

5. Fish disease prevention and control

Yellow catfish in natural waters rarely develop diseases, but intensive high-density artificial rearing is prone to outbreaks of bacterial diseases and parasitic diseases. Frequently washing and cleaning the feeding platforms, removing residual bait, and disinfecting the feeding platforms are effective preventive measures. During the rearing period, regularly disinfect the water body, such as splashing the whole pond with 0.3 mg/L strong chlorinated powder or 20 mg/L formaldehyde, or 0.7 mg/L copper sulfate and ferrous sulfate mixture, combined with oral furazolidone (add 0.5 g per kg of feed, feed continuously for 7 days), which has a good preventive and control effect. If the disease is severe, fish can also be gathered with a seine net and bathed in 50—60 mg/L formaldehyde for 5 minutes. In addition, every half month apply 15 kg of quicklime per 667 sq m, which can both regulate water quality and prevent the spread of fish diseases.