Application of Artificially Hatched Artemia in Industrialized Cultivation of Yellow Catfish Fry

1. Wide-ridge double-row planting method: This method transplants rice seedlings in a sequence of 6 cun, 12 cun, 6 cun. Its advantages: First, the total number of hills per mu (16,000 hills) is slightly less than that of monoculture rice, but yield increases through ventilation and light penetration; Second, it provides more than 7 hours of light daily, raises water temperature, and allows plankton to reproduce and grow rapidly, creating good conditions for providing natural food organisms for yellow catfish; Third, it broadens the activity space for yellow catfish, enables large-scale pest elimination, and fish feces serve as fertilizer, increasing rice yield.

2. Rice management: Rice cultivation management strictly follows "NY/T5117-2002 Pollution-Free Food" and rice production technical regulations. First, timely and rational fertilization: official transplanting on May 18; 1 day before transplanting, apply base fertilizer of urea 2.5 kg/mu and diammonium 5.0 kg/mu; 3 days after transplanting, apply green-turning fertilizer of urea 3.0 kg/mu; thereafter apply urea once every 7 days, with the first application at 4.0 kg/mu, the second at 6.0 kg/mu, and the third at 8.0 kg/mu. Second, rational use of biotechnology: photosynthetic bacteria are also used during rice cultivation. When soaking rice seeds, soak for 7 days in water with 20% by volume photosynthetic bacteria solution; when raising rice seedlings, spray 50 g/sq m photosynthetic bacteria on the seedbed (nursery bed); when rice seedlings grow to the two-leaf-one-heart stage, spray 5 g/sq m photosynthetic bacteria; 2 days before transplanting, spray 10 g/sq m photosynthetic bacteria on the seedbed once; at the tillering stage, jointing stage (early July), and booting stage (mid-August), spray 1000 g/mu photosynthetic bacteria.

7. Harvest

Harvest began in early October. The total area was 65 hectares, with a total rice harvest of 526,500 kg, valued at 947,700 yuan, with costs of 429,000 yuan and profit of 518,700 yuan; total yellow catfish output was 21,450 kg, with an output value of 858,000 yuan, costs of 305,000 yuan, and profit of 553,000 yuan. The comprehensive rice-fish benefit was 1102 yuan/mu, an increase of 524 yuan/mu in profit compared with monoculture rice.

The average grow-out size of yellow catfish was 110 g/fish, of which: 50 g/fish to 74 g/fish accounted for 5%, 75 g/fish to 99 g/fish accounted for 25%, 100 g/fish to 149 g/fish accounted for 55%, and 150 g/fish and above accounted for 15%. The rice planted in the yellow catfish rice-field ecological culture model had large panicles and many grains, higher than monoculture rice, and the rice processed from the planted rice fully met pollution-free food standards.

8. Existing problems

1. The size of yellow catfish fry was too small, only 6 g/fish, directly affecting culture yield.

2. Some culture plots had insufficient feed supply, with grow-out size only 50 g/fish to 60 g/fish.

3. The inlet protective net was improperly set up. Because the mesh was too large, wild miscellaneous fish entered the field and competed with yellow catfish for food, causing slow growth of yellow catfish due to insufficient food intake.

9. Summary

1. Rice-field engineering is the foundation. The larger the water body, the greater the biological load capacity, the better the water environment, and the more stable the yield.

2. Based on ecological and biological principles, establish and promote the yellow catfish rice-field ecological culture model, forming a food chain structure and a good ecosystem in which rice protects fish, fish eat insects, and fish feces increase fertility and thus enhance soil fertility.

3. The use of photosynthetic bacteria in culture can not only purify water quality and reduce pollution, but also prevent diseases, producing pollution-free rice and yellow catfish, achieving the goal of a win-win for rice and fish.

The stage from water fry to fry is a critical period in yellow catfish seedling cultivation, and the selection of first-feeding bait has always been a technical difficulty troubling yellow catfish seedling culture. In order to explore large-scale, industrialized production technology for yellow catfish fry, in recent years we used artificially hatched Artemia to conduct yellow catfish fry cultivation trials, and over 2 years cultivated a total of 2.64 million yellow catfish fry, with an average cultivation survival rate of 61.6%.

1. Preparation of cultivation ponds

There were 17 indoor cement cultivation ponds in total, rectangular, 2 m x 6 m, 1.2 m deep, capable of holding water 1.0 m deep. A shower-type water inlet pipe was at one end, and the outlet at the other end was closed with a 60-mesh sieve silk frame-type fish-blocking screen. Three days before stocking fry, the ponds were filled with water and disinfected with 1 ppm strong chlorinated disinfectant.

2. Stocking of yellow catfish water fry

The yellow catfish water fry were bred by a local seedling breeding farm. In the first year, a total of 12 batches and 1.925 million water fry were stocked; in the second year, a total of 15 batches and 2.36 million water fry were stocked. The stocking density of water fry was 3500 fish/sq m to 7000 fish/sq m.

3. Cultivation of Artemia

Artemia cysts were canned, with a specification of 425 g/can. Artemia hatching began 24 hours before the yellow catfish water fry were stocked into the ponds. A 100 kg capacity plastic bucket was filled with water, 2 kg to 3 kg of table salt was added, and 212 g (half a can) of Artemia cysts was placed in each bucket. The cultivation buckets were placed in a constant-temperature flowing water pool, with water temperature maintained at (26 plus or minus 1) degrees C, and oxygen was supplied with an air pump, with at least 2 air stones placed in each bucket. According to the number of yellow catfish being cultivated, Artemia were cultivated in several batches to ensure the supply of food organisms.

4. Feeding of Artemia

Artemia hatching generally takes 24 hours to 30 hours. Newly hatched Artemia have a relatively pale body color; when placed in a beaker in sunlight, Artemia can be observed with the naked eye. Feeding can begin immediately after the yellow catfish water fry are stocked into the ponds. Generally, feeding was done 3 times per day. At the beginning, for every 10,000 yellow catfish water fry, the daily feeding amount was 15 g to 20 g of Artemia hatched from Artemia cysts. Thirty minutes after feeding Artemia, the feeding condition of the yellow catfish fry was observed. Fry that had eaten their fill had round, bulging abdomens appearing orange-red. As the fry grew, their food intake continuously increased. It was required to frequently observe the satiation level of the yellow catfish and promptly increase or decrease the feeding amount. If most fry sank to the bottom after feeding or attached to the pond walls, it proved that the fry were full. If after 30 minutes of feeding most fry were still swimming on the water surface with empty, shrunken abdomens, it indicated that the feeding amount was insufficient and should be increased. After 5 days of water fry cultivation, cladocerans and other zooplankton collected from ponds could be appropriately fed to supplement the insufficiency of Artemia.

5. Culture management

1. Control the flow rate of pond water well, especially reducing the flowing water volume when feeding Artemia, to prevent Artemia from flowing out of the fish pond with the water flow. Generally, normal water injection was restored 30 minutes after feeding.

2. Promptly remove Artemia cyst shells from the pond water to prevent them from being mistakenly eaten by yellow catfish fry.

3. Gently brush the fish-blocking screen once every 2 hours to 3 hours to maintain water permeability.

4. Water temperature was required to be maintained at around 25 degrees C. Dissolved oxygen and water temperature were measured morning and evening each day, and culture records were kept well.

5. Regarding disease prevention and control, 35 ppm formaldehyde could be splashed over the whole pond once every 3 days, and sterilization drugs could be splashed over the whole pond once every 2 days.

6. Net-pulling exercise and @#@136@#@

When the yellow catfish grew to a body length of 2.0 cm to 2.5 cm, they could be taken out of the ponds for sale, and 1 to 2 net-pulling exercises were performed 1 day before sale, while reducing the feeding amount of food organisms by 50%.

7. Trial results

In the first year, 12 batches of fry were produced, 1.92 million water fry were stocked, 1.03 million fry were produced, and the cultivation survival rate was 53%; 39.1 kg of Artemia cysts were consumed, with an average of 380 g of Artemia cysts consumed per 10,000 fry produced, and the food organism cost was 58 yuan per 10,000 fry. In the second year, 15 batches of fry were cultivated, 2.366 million water fry were stocked, 1.61 million fry were produced, and the cultivation survival rate was 68%; a total of 65.87 kg of Artemia cysts were fed, with 409 g of Artemia cysts consumed per 10,000 fry produced, and the food organism cost was 63 yuan per 10,000 fry.

8. Analysis and discussion

1. Using artificially hatched Artemia to industrially cultivate yellow catfish fry in northern regions can improve the cultivation survival rate from yellow catfish water fry to fry, is not affected by weather, temperature, and other environmental conditions, allows all-weather production, and facilitates centralized sales, benefiting users.

2. The suitable stocking density of yellow catfish water fry is 3500 fish/sq m to 5000 fish/sq m. Too low a stocking density wastes water volume, while too high a density easily causes fry hypoxia and floating to the surface, and the size differences among fry are relatively large, reducing the cultivation survival rate. In the trial, the cultivation survival rate was only 61%. The main reason for the relatively low cultivation survival rate was that the quality of yellow catfish water fry was not high, with deformed fry accounting for a relatively large proportion (10% to 15%). After deformed fry were stocked into ponds, they died because of incomplete organ development and difficulty feeding.

3. The cultivated Artemia should generally all be fed out within 24 hours to 36 hours, and it is not suitable to feed too early or too late. Within this time period, the maximum hatching rate and survival rate of Artemia can be ensured, and it is also relatively suitable for the mouth size of yellow catfish. When feeding, splash it into the pond together with the salt water used for cultivation, which can improve water quality and prevent disease and eliminate pests.

4. During the cultivation of yellow catfish fry, no diseases with relatively great harm occurred. Chilodonelliasis caused by feeding zooplankton collected from ponds could be promptly eliminated by splashing a mixture of copper sulfate and ferrous sulfate; or when feeding collected zooplankton, first disinfect with a mixture of potassium permanganate, copper sulfate, and ferrous sulfate for 10 minutes, then feed, which can basically eliminate the occurrence of chilodonelliasis.

5. Using artificially hatched Artemia to cultivate yellow catfish fry does not have high feed costs, only about 60 yuan per 10,000 fry, accounting for less than 10% of the total cost of fry cultivation. Most of the cost is determined by expenses for breeding yellow catfish water fry, water and electricity fees, labor fees, and so on, while the selling price of yellow catfish fry is generally 1500 yuan per 10,000 fry to 1700 yuan per 10,000 fry. It can be confirmed that using Artemia to cultivate yellow catfish fry is technically feasible and also very considerable in terms of benefits.