Detailed explanation of key technical points for commercial adult fish farming of the red-eye carp (Squaliobarbus curriculus)
Stocking density for commercial fish farming ponds
When raising from fry of 3-4 cm total length to commercial fish of over 600 g individual weight, 20,000-25,000 fish can be stocked per mu of effective water surface (excluding polyculture fish). The red-eye carp in the pond can be harvested in batches when they reach 20 fish/jin, 10 fish/jin, and 5 fish/jin respectively for market sale, and finally about 1,800-2,000 fish/mu are retained to grow into large-size commercial fish of over 600 g.
Nutritional indicators of feed
Under pond farming conditions, artificial compound pellet feed is mainly used, and the animal protein content in the compound feed at each stage should preferably account for more than 1/3 of the total feed protein.
The nutritional indicators at each stage are: from summer fry to fingerling stage, the rearing period is 100-110 days, and the crude protein content in the compound feed at this stage should reach 30-34%; from fingerling to adult fish stage, the rearing period is 120-160 days, and the crude protein content in the compound feed at this stage should reach 28-32%.
Feeding methods for commercial fish
1. Stocking density in main culture ponds: provided the pond meets the required conditions, 1,800-2,000 large-size fingerlings with an average individual weight of 40-60 g and a total length of over 12 cm can be stocked per mu of effective water surface, and additionally 100-130 silver carp of the same age, 30-40 bighead carp, and 50-100 crucian carp can be polycultured.
2. Domestication and feeding: The red-eye carp is highly sensitive, easily rises to the surface, responds to domestication, prefers floating feed, tends toward herbivorous habits, and is easy to raise. In terms of feeding, do not rush to feed the fingerlings just placed into the pond, because after transfer between ponds or transport from elsewhere, they are startled and uncomfortable; the fingerlings just placed in the pond have not yet adapted to the environment, and since the stress response has not yet been eliminated and their constitution has not yet recovered, they will not eat immediately. After the fingerlings are placed in the pond, they should be left undisturbed for 2-3 days to adapt to the environment before starting domesticated feeding. The method is to first set up 4-5 feeding points around the pond, rouse the fish by clapping or playing sounds, and then train the fish and feed them; at this time, feed twice a day, once in the morning and once in the afternoon. After 3-4 days of domesticated feeding, most of the pond fish can gather in schools and rise to the surface to compete for food at the feeding points; then switch to the already prepared feeding table for formal feeding.
3. Fish body size and feed particle size: when the individual weight of the fish is below 100 g, crushed palatable pellet fragments should be fed; when the individual weight grows to 100-300 g, to suit the mouth shape, artificially compounded pellet feed with a particle diameter of 1.0-1.5 mm should be fed. When the individual weight grows to 300-600 g, artificially compounded pellet feed with a particle diameter of 1.5-3.0 mm should be fed. Because this fish is a population inclined toward herbivorous habits, during the rearing process from fingerling to adult fish, an appropriate amount of green feed should be fed (such as small duckweed, purple-backed duckweed, Hydrilla verticillata, dew-grown ryegrass, vegetable leaves, and tender grass, etc.). This can both meet the nutritional needs of its growth stages and effectively reduce feed costs (when feeding fresh tender dew grass in spring and early summer, it should be chopped before feeding; by midsummer, when the individual weight of the fish grows to over 150 g, it can be fed directly).
4. Feeding time and feeding amount: when the spring water temperature reaches above 10°C, this fish has already begun to seek food, and at this time trial feeding can begin in the pond, with the purpose of inducing it to start eating earlier. This stage is the trial feeding and domestication feeding stage, feeding once a day at 2-3 pm.
When the water temperature rises to 14-18°C, the daily feeding frequency should be changed to 2 times, namely 10-11 am and 3-4 pm; when the water temperature rises to 18-30°C, the daily feeding frequency is 3 times, namely 7-8 am, 11 am-12 noon, and 4-5 pm, or it can be changed to feeding pellet feed once each in the morning and afternoon, and feeding green feed once in the evening.
If there is no green feed, the times for the 3 daily feedings should be changed to 8-9 am, 11 am-12 noon, and 4-5 pm.
In autumn, when the water temperature drops below 8°C, this adult fish is basically in a state of not eating.
For this fish in spring when the water temperature is 10-14°C, the daily feeding amount is 0.3-2% of the total body weight of the pond fish; when the water temperature rises to 14-18°C, the daily feeding amount is 2-5% of the total body weight of the pond fish; when green feed is sufficient, the daily feeding amount is 8-13% of the total body weight of the fish; while feeding green feed, reduce the artificially compounded pellet feed by 8-10% of the original daily feeding amount.
When the pond fish have been domesticated to rise to the surface, gather in schools, and compete for feed, they should immediately be transferred to the previously prepared feeding table for centralized feeding. In feeding techniques, the feeding method should be adopted of going from slow to fast, from fast to slow, from less to more, and from more to less, and the feed should also be scattered over a wide and even area; from fingerling to adult fish, it is best to use a feeding machine to feed on schedule.
5. Raw materials and quality: the main feed raw material sources for rearing include fish meal, soybean meal, rapeseed meal, peanut cake, wheat bran, rice bran, wheat middlings, and other minerals and trace elements. However, the raw materials must be fresh, non-rotting, and non-contaminated; the use of deteriorated raw materials is strictly prohibited; and it is required that the protein content in the compound feed for red-eye carp at the juvenile stage should remain at 30-32%, and at the adult fish stage should remain at 28-30%. The green feed fed must have no pesticide residues, not be aged, not be rotten, and not be moldy, ensuring freshness, to avoid poisoning or disease in the pond fish.
6. Water quality regulation: during the rearing stage from fingerling to adult fish, this fish has a slightly weaker tolerance to low oxygen than other conventional fish, and the water quality and water level of the farming pond must be carefully adjusted.
Starting from the completion of the first water filling before fingerling stocking and the beginning of feeding when the water temperature reaches above 10°C, under normal circumstances, add new water once every 10-15 days, and each addition should be no less than 10-15 cm. As the dual temperatures rise, gradually raise the pond water level, especially during midsummer, when the pond water level should be controlled at a maximum of over 2.5 m.
As the fish grow, their food intake increases, and the excretory substances in the pond water relatively increase. In addition, some humic substances need oxygen to decompose and transform, which increases oxygen-consuming factors. Therefore, in pond water quality management, pond water quality monitoring and regulation should be done promptly according to weather conditions and water quality changes.
Add new water in a timely manner so that the water quality of the farming pond remains good over the long term, and the dissolved oxygen content must reach above 4 mg/L; discharge part of the old water from the pond and add enough new water. Keep the rearing pond water quality tender, lively, fertile, and refreshing during the farming period.
Feed feeding
The crude protein content of the artificial compound feed for adult red-eye carp should be about 28-30%, and the feed conversion ratio should be about 1.8. The raw materials of the compound feed are required to meet specifications, and raw materials that have been damp, moldy, insect-infested, spoiled and deteriorated, or contaminated by petroleum, pesticides, harmful metals, etc. must not be used.
Feeding should follow the scientific principles of the "four looks" and "four fixeds", and the amount fed each time should be flexibly controlled. During the main growing season, feed once each in the morning and afternoon every day, and generally the amount fed each time should be eaten within about 20-30 minutes after feeding. In addition, according to the feeding habits of the red-eye carp, some green feed should also be fed, such as duckweed and other aquatic plants and green grasses, so as to promote its growth, reduce feed costs, and improve economic benefits.
Disease prevention and control
The red-eye carp is a variety with relatively strong disease resistance among freshwater farmed fish, and from fry (water fry) to adult fish it rarely becomes diseased. However, under the conditions of intensive farming in pond water bodies, due to factors such as relatively high stocking density, farming water not being completely good, and management techniques not yet being perfect, it is difficult to avoid the occasional occurrence of some common disease types, such as parasitic Dactylogyrus, Trichodina, Gyrodactylus, and Lernaea. In water environments with extremely poor water quality, bacterial diseases also occur, such as gill rot and enteritis.
Throughout the entire rearing process, adhere to the principle of "prevention first, prevention more important than treatment"; in disease prevention and control, do the following work well:
Thoroughly clear the pond and disinfect the fingerlings; do not feed deteriorated or moldy bait or unclean green feed; add water or replace with new water in a timely manner, and increase the pond water storage capacity during high-temperature periods;
For water body disinfection during periods when fish diseases are prone to occur, every 15-20 days use quicklime at 10-12 kg per mu of effective water surface, or use bleaching powder (with a chlorine content above 30%) at 0.8-1.0 ppm, add an appropriate amount of water and thoroughly dissolve it into a medicinal slurry or liquid, and splash it over the whole pond;
Keep the pond water clean, maintain pond environmental sanitation, promptly clean up residual bait on the feeding table, remove dirt from the pond, and remove weeds around the pond to ensure pond environmental sanitation;
Persist in pond patrols, use drugs according to the symptoms, use drugs according to the fish, and use drugs prudently. The red-eye carp is extremely sensitive to copper sulfate, and copper sulfate is prohibited in main culture ponds; other drugs are largely the same as those for conventional fish. The more commonly used and safe drugs include: quicklime, bleaching powder, trichlorfon, oxytetracycline, baichongsha, povidone iodine, etc.
Daily management
During the main growing season, persist in patrolling the pond every morning and evening, carefully observe the fish's activities, feeding, and water quality, and keep pond records. During high-temperature seasons, pay attention to timely water changes, generally adding and changing water once about every 10 d, to maintain fresh water quality and relatively high dissolved oxygen.
During the growing season, turn on the aerator every day from 1-3 pm, and once floating head is found, turn on the aerator promptly. About every 20 days, use 20 g of quicklime per cubic meter of water, dissolve it, and splash it over the whole pond to regulate water quality.
To prevent bacterial diseases, a bactericidal disinfectant can be splashed over the whole pond once a month (May-September); for parasitic diseases, avermectin can be splashed over the whole pond; if infected with Lernaea disease, splash once more after an interval of 5-7 d. Before adult red-eye carp are marketed, the corresponding withdrawal period regulations should be observed and drug use stopped to ensure the quality of the marketed fish.
Precautions
Cage farming of commercial red-eye carp requires a cover net, because this fish likes to jump; pond farming of this fish during the fry and fingerling stage requires increased stocking density, and 25,000-30,000 fish can be stocked per mu, and after they grow to about 60-70 fish per unit, they can be divided into ponds to farm commercial fish; during intensive pond farming, when feeding, the machine should be run for about 10 minutes at a time, and it is better to run it again for about 10 minutes after a few minutes.