Detailed Explanation of Key Techniques for Squaliobarbus curriculus Fry and Fingerling Rearing

1. Rearing pond: area 3-5 mu, water depth 1.8-2.2 m, pond cleared and disinfected with bleaching powder, water intake filtered.

2. Water quality cultivation: 3-5 days before the fry are stocked, apply 150 kg of thoroughly fermented chicken manure; the water turns oily green, the water quality is fresh and lively, with transparency of about 30 cm. After the fry are stocked, use it together with soybean milk to maintain good water quality. Because the mouth opening of newly hatched Squaliobarbus curriculus fry is small, they can only feed on small plankton at first feeding, so the base fertilizer should not be applied too early.

3. Newly hatched fry stocking: 1 day before stocking, conduct a “test water” check to detect whether the toxicity of the pond-clearing chemicals has dissipated, and at the same time use a fine-mesh net to drag 1-2 times across the whole pond to remove frog eggs, tadpoles or other harmful organisms. Choose a sunny morning for stocking; if the newly hatched fry are purchased from outside, first soak the nylon bags containing the fry in the pond water for 0.5 h to adjust the temperature difference. Newly hatched Squaliobarbus curriculus fry are very delicate, so handling must be done with great care, and the temperature difference at stocking should not exceed 2°C. The stocking density depends on pond conditions and the level of farming technology; generally 100,000-150,000 fry can be stocked per mu.

4. Stocking density: under normal circumstances, fry (newly hatched fry) with a total length of 0.7-0.72 cm at stocking are reared to summer fingerlings with a total length of 1.7-3.0 cm, and 150,000-200,000 fry can be stocked per mu of effective water surface.

5. Feeding management: On the day the newly hatched fry are stocked, begin broadcasting soybean milk over the whole pond. Use 4-6 jin of dry soybeans per mu of water surface per day, grind into milk in 2 batches and broadcast over the whole pond. In the middle and late stages of summer fingerling rearing, apply additional fertilizer as appropriate according to water quality, and gradually reduce the amount of soybean milk while increasing the feeding amount of powdered fine feed (such as wheat middlings, fine rice bran, etc.), generally feeding 4- jin per mu of water surface per day to ensure the fry receive sufficient feed. After 10 days, add soybean meal powder and wheat middlings mixed with water and feed them along the water edge in intermittent strips and spots, and gradually reduce the use of soybean milk. Then gradually transition to feeding micro-pelleted floating compound feed; after five or six days, use micro-pelleted feed entirely, feeding once each morning and afternoon, with the feeding amount based on the feed being basically finished within 20 minutes. Precautions: From the time the fry (newly hatched fry) are put into the rearing pond, the first broadcast of soybean milk over the whole pond can be done carefully and evenly after 2 hours. Ponds stocked in the morning should be fed soybean milk 2-3 times that day, and ponds stocked in the afternoon should be fed 1-2 times that day. From the morning of the 2nd day of rearing, feed 3 times a day, namely 8-9 a.m., 12 noon-1 p.m., and 4-5 p.m., broadcasting evenly over the whole pond. After 3 consecutive days of broadcasting soybean milk, depending on the fertility of the pond water and the amount of biomass (especially the amount of rotifers), the daily amount of soybean milk broadcast may be appropriately reduced. If the rearing pond water has already become fertile, the number of daily soybean milk broadcasts can be changed to 2 times, namely 9-10 a.m. and 3-4 p.m. After 10-12 days of rearing the fry (newly hatched fry) in soybean milk water, the fish body has grown to a total length of 0.8-1.2 cm; at this time, artificially prepared powdered feed (such as cooked oil wheat flour, oil fine wheat bran, oil fine rice bran, etc.) should be added to the pond in a timely manner. When the weather is good with a light breeze or no wind, use the hand to scatter the powdered feed at fixed points around the pond in appropriate amounts. If fish float up to feed after scattering, the feeding frequency and feeding amount should be appropriately increased. Each application of powdered feed should preferably be completely eaten within 20-30 minutes. When the fry have been reared for about 20 days, the amount of soybean milk should be reduced in a timely and appropriate manner according to whether the pond water is fertile or lean. At the same time, change the daily powdered feed to crushed artificial compound pellet feed with powdery fine particles. The daily feeding amount is 4-12 jin per mu of effective water surface.

6. Water quality regulation: Throughout the entire nursery period, attention must be paid to the management and regulation of water quality. Generally, as the fry grow, new water is frequently added to slowly raise the water level. In the later stage of nursery rearing when the water is relatively fertile, raise the water level to the maximum to ensure the water quality is “fertile, lively and fresh”. In daily management, persist in patrolling the pond twice a day in the morning and evening, carefully observing fry activity, feeding and changes in water quality, and promptly solving problems as they are found. As the fry grow larger and feed input increases day by day, oxygen-consuming factors in the rearing pond gradually increase; at this rearing stage, management of water sources and water quality must be strengthened. In order to expand the rearing space, increase the water-holding capacity of the rearing pond, and regulate water quality, the pond water level should be raised in a timely manner to improve the water quality environment of the rearing pond, increase dissolved oxygen in the pond water, and keep the pond water both fertile and lively. Add water once every 5-7 days, 5-10 cm each time. Use biological bacteria once every 15 days to keep the water quality fresh and lively, with transparency of 25-30 cm, dissolved oxygen of 4-5 mg/L, and pH of 7.0-7.6.

7. Pond splitting and stocking: After 25-30 days of rearing, the newly hatched fry generally reach a body length of 3-3.5 cm; at this time they should be sold or split into other ponds in a timely manner and transferred to the fingerling rearing stage. If summer fingerlings are to be transported over long distances, they still need 2-3 times of net-pulling exercise before leaving the pond, but operations must be careful to avoid external injuries as much as possible, so as to improve the survival rate of pond removal and transportation. After net-pulling and pond splitting, continue feeding floating feed, supplemented with a small amount of duckweed. Throughout the whole process from fry to summer fingerlings, management must be strengthened. Persist in patrolling the pond in the morning and evening, carefully observe whether there are abnormal phenomena in the pond fish's activity and feeding behavior, and whether there are changes in water quality and water level; once abnormal problems are found, promptly take effective measures to solve them. Precautions: Because this is a season of both high air temperature and high water temperature, Squaliobarbus curriculus at the summer fingerling stage are quite delicate, agile in activity, good at jumping, and quick in swimming. During the entire process of fish training, net transfer, and pond removal for sale, operations should be careful and meticulous, trying to avoid injury to the fish body, so as to improve the survival rate of pond removal, pond transfer, sale, and transportation.

8. Autumn fingerling rearing: From summer fingerlings to autumn fingerlings, in addition to stocking 12,000-15,000 summer fingerlings of 2.0-3.0 cm per mu of effective water surface, 200 silver carp of the current year may also be added, but no other species may be added. The rearing mainly consists of feeding powdered feed → crushed feed → pellet feed.

1) Feeding and rearing: In the initial stage of summer fingerling stocking, the feed must be palatable, preferably powdery floating powdery small crushed feed. For every 10,000 summer fingerlings, feed 300-350 g per day, increasing the feeding amount once every 5-7 days, with the increase gradually rising by 5-7% of the total feeding amount of the previous 5 or 7 days, so that the daily food intake of the pond fish accounts for 14-7% of the total weight of the pond fish, with 3-4 feedings per day, namely 7-8 a.m., 10-11 a.m., 1-2 p.m., and 4-5 p.m.; or 7-8 a.m., 11 a.m.-12 noon, and 3-4 p.m.; when the summer fingerlings grow to more than 5 cm, change the original 3-4 feedings per day to 3 feedings per day, namely 8-9 a.m., 12 noon-1 p.m., and 4-5 p.m.; it may also be changed to feeding pelleted feed once each in the morning and afternoon, namely 8-9 a.m. and 2-3 p.m., and feeding small duckweed once at 5-6 p.m. The daily feeding amount of fine feed is 7-4% of the total weight of the pond fish. The exact daily feeding amount should also be flexibly controlled according to the weather, water temperature, water quality, dissolved oxygen level, pond fish activity, feeding behavior and other conditions of the day. Each time the fish are fed, it is preferable that all the feed applied (except small duckweed) is completely eaten within 50 minutes. The daily feeding amount of green feed depends on the feed source, but for fresh small duckweed, the daily feeding amount must not exceed 12% of the total weight of the pond fish, and it is best to feed it every evening.

2) Water quality regulation: Throughout the whole process from summer fingerlings to fingerlings, the water quality of the rearing pond should always be maintained in good condition. Under normal circumstances, add new water once every 10-15 days, and each addition must be no less than 10 cm. Once sudden changes occur, the amount of water added or exchanged must be increased; especially in the midsummer season when both air and water temperatures are high, the pond water level should be raised to the highest point to expand the rearing space and increase dissolved oxygen in the pond.

3) Daily management: The period from summer fingerling rearing to autumn fingerlings coincides with the midsummer season of changeable weather and unstable climate. During this period, great importance must be attached to the daily management of the rearing pond:

a. Manage the pond water level and water quality well, and add new water or exchange part of the old water in a timely manner;

b. Keep the dissolved oxygen content in the rearing pond water body above 4 mg/L for a long period;

c. Feed the fish according to the weather; in terms of feeding quantity, not only grasp the “four fixed” principles, but also pay attention to observing weather changes, and feed the fish according to the sky, the water, and the situation. Squaliobarbus curriculus are sensitive and active, have strong food-grabbing ability, and are also greedy feeders; their oxygen consumption rate is somewhat higher than that of other conventional fish. For this reason, on muggy and rainy days they must not be allowed to spend the night with a full belly;

d. Turn on mechanical aeration in a timely manner to strictly prevent pond fish from gulping for air; persist in pond patrol work, and throughout the entire rearing process persist in patrolling the pond in the morning, at noon, and in the evening, carefully observing changes in the pond water and whether there are abnormal phenomena in fish school activity.

Using the above methods, from summer fingerlings to the current year's autumn and winter, the survival rate can reach more than 90%, the fingerling size can reach an overall average total length of more than 12 cm, the average weight per fish can reach more than 40-60 g, and the yield of fingerlings per mu can reach more than 1,500 jin.

9. Winter fingerling rearing: Basically similar to summer fingerling rearing, but the stocking density is controlled at about 10,000 fish per mu. In addition, as the fry and fingerlings continue to grow, compound feed and an appropriate amount of green feed (such as duckweed, Hydrilla verticillata, etc.) must also be fed. As long as feed is sufficient and water quality is good, Squaliobarbus curriculus summer fingerlings reared to the end of the year can all reach a size of more than 12 cm, and can be used as fingerlings for grow-out the following year.

During the fry and fingerling stage, Squaliobarbus curriculus has a relatively fast growth rate. After a rearing period of 70-80 days, the fingerling size can all reach more than 10 cm, and the survival rate is more than 90%.