Experience in Rearing Yellow Catfish Fingerlings in Ponds
Based on the characteristics at this stage, such as the increased size of yellow catfish fry, feeding habits basically similar to those of adult fish, stronger schooling behavior, increased food intake, and stronger adaptability to the ecological environment, and given that water temperatures are generally high during the rearing process, it is necessary to take into account the characteristics of yellow catfish and grasp several key technical steps in order to obtain high-quality fingerlings with a high survival rate and robust constitution. Rearing can be carried out in ponds or cages, but note that the area of ponds used for fingerling rearing should not be too large, otherwise it is not conducive to feeding and daily management.
1. Pond conditions and clearing The rearing pond area is generally most suitable at 1-2 mu, because if the area is too large, it easily causes uneven feeding among the fingerlings and brings difficulties to harvesting operations. The pond water depth should be about 1.5 m, the pond bottom should be flat, and it is ideal for about 20% of the area around the drainage outlet to be lowered by about 20 cm. There should be little silt, good water retention performance, convenient water inlet and drainage, a quiet surrounding environment, and some slight shading. Before stocking fry, the pond must first be cleared of wild fish and disinfected, and fry should be stocked after zooplankton has been cultured.
2. Fry stocking Stock small-sized summer fry of about 2 cm (also called fire-fry), requiring uniform size, robust constitution, no injuries or disease, agile swimming, and vigorous movement, and the fish bodies should undergo strict medicated bath disinfection. The stocking density of fry should be determined according to production conditions and pond conditions. Generally, when fingerlings are to be reared until around overwintering and then stocked into adult fish ponds for grow-out, the rearing density is relatively high, with a stocking rate of 8,000-10,000 fish per mu. If rearing for a short period until July-August and then dividing into ponds for commercial fish rearing, the stocking rate is 4,000-6,000 fish per mu. When the fingerlings grow to 8 cm, they can be divided into ponds and then placed into adult fish ponds for grow-out.
3. Feed and feeding When stocking 2 cm fry, the amount of zooplankton in the pond can basically meet their needs for several days. When the fingerlings are between 2-3 cm, the best feeds are live feeds such as rotifers, copepods, cladocerans, chironomid larvae, and tubifex worms. As individuals grow larger, natural food in the pond decreases, and artificial mixed feed must be provided to meet the feeding needs of the fry. First, set up a feeding platform in the pond. The materials should be bamboo mats, straw mats, colored striped cloth, etc. The area of the feeding platform per mu of pond should be about 6-8 sq m, and the feeding platform should preferably be able to be raised and lowered. Fix the feeding platform with bamboo stakes at about 10-20 cm from the pond bottom, then place the feed on the feeding platform. There are the following three methods for preparing feed:
(1) A method more commonly used in production is to mince small trash fish, mix in some fish meal, silkworm pupa powder, soybean powder, wheat bran, and third-grade flour, and knead into a dough-like feed for feeding. The fish can also be minced into a paste and directly fed after binding with third-grade flour.
(2) Mix powdered raw materials evenly, add a certain amount of water, knead into dough, and feed.
(3) Artificially compound and process into pellet feed, then crush into micro-pellet feed for feeding.
The preparation method for the latter two compound feeds is: fish meal 23%, silkworm pupa powder 8%, meat and bone meal 8%, blood meal 8%, yeast powder 6%, soybean powder 17%, standard flour 23%, vegetable oil 3%, vitamin mixture 1%, mineral mixture 1.5%, and binder 1.5%. In addition, many farmers use small trash fish minced into meat paste and directly feed it into the pond. As for feeding amount and frequency, the feeding amount is generally 10% when feed conversion begins, and later gradually decreases to 5%-6% of body weight. Feed 2-4 times per day. Before reaching 3 cm in length, feed 3-4 times per day; before reaching a total body length of 5 cm, feed 2-3 times per day; afterward, feeding 2 times per day is sufficient. The nutritional standards for compound feed for yellow catfish fingerlings are: crude protein 40%-43%, fat 8%-10%, carbohydrates 18%-23%, and fiber 3%-5%.
4. Daily feeding management Throughout the entire fingerling rearing process, daily pond management is a meticulous, multifaceted, and routine task, and is the key to increasing the survival rate of fingerlings and enabling them to reach large size.
(1) When feeding every day, special attention must be paid to the “four fixeds”, namely fixed time, fixed location, fixed quantity, and fixed quality.
(2) Clean the feeding area once every 3-5 days, and disinfect once every half month with bleaching powder (0.3-0.5 kg). If pellet feed is used, the frequency can be appropriately reduced. Frequently remove weeds around the pond and decaying filth in the pond, maintain pond environmental sanitation, and prevent the breeding of harmful insects and pathogens.
(3) Patrol the pond once every morning to observe water color and fish activity, especially the floating-head situation. If floating head is relatively serious, add fresh water in a timely manner. Observe changes in water quality and control the amount of fertilization and feeding. In the afternoon, patrol the pond in conjunction with feeding or checking feeding conditions, so as to discover problems and solve them in a timely manner.
(4) During the fry rearing period, it is also the peak period for the reproduction of tadpoles and various harmful aquatic insects. Tadpoles in the pond should be removed at any time to prevent them from competing for the fingerlings' feed. When enemies such as water snakes, water centipedes, and dragonfly larvae are found, they should be dealt with in a timely manner. In areas with many water birds, effective measures should be taken to drive them away and kill them.
(5) Add water at appropriate times to improve water quality. With large daily feeding amounts in the pond and much excrement, pond water can very easily become too fertile. Therefore, frequently adding water can improve water quality, prevent oxygen deficiency and pond die-off, and promote fish growth. During the rearing period, generally add water once every 10-15 days.
(6) The fingerling rearing stage is the period when fish diseases are most likely to spread. During this period, attention should be paid to observation and various preventive measures should be adopted. The most common disease of yellow catfish during this period is hemorrhagic edema disease. In addition to using disinfectants in the pond to eliminate bacteria, tetracycline should also be added to the yellow catfish feed, adding 20 g per kg of feed for feeding, once a day, for 3-5 consecutive days.