In recent years, the model of raising catfish in earthen ponds is receiving great attention from farmers. The technique of raising cotton fish is not much but requires high accuracy. To learn more about Technique of raising cotton fishfarmers do not rush to skip the article below.
Choose brood fish
The broodstock are selected in the wild from fishing boats, choose healthy individuals, have few scratches, keep the fish in the tank with continuous aeration for 3-4 days for the fish to be completely healthy and then transported to domestication. . Fish are raised with some gluttonous fish such as carp and sesame with a density of 5-10 kg/m3. Use pellets with protein content of 28 – 30%, daily ration 2 – 3%.
After that, the broodstock are reared and matured in rafts placed on the river, the size (8x4x3)m= 96 m3, the rafts are placed floating and anchored on a fixed river where the flow is straight and continuous. The place where the raft is placed does not affect traffic, the river water where the raft is located is not alum, salty, far from sewage and convenient in traffic and food transportation.
The selected broodstock are numbered for the brood with a pointed stick numbered on the head of the fish (using normal numbers for female fish, Roman numbers for male fish). The broodstock rearing season is from December of the previous year to mid-November of the following year. The fish matures and starts spawning from August. The spawning season lasts until early November.
On the outside, it is very difficult to distinguish male and female from the outside. When it comes to the breeding season, there is an outward appearance, specifically, the male fish has a slightly rounded protruding genital opening, while the female fish has a slightly more concave genital hole than the male fish.
Select male fish that are healthy individuals, claws on the abdomen near the genital opening with milky white semen flowing out. Select female fish that are large-bellied individuals, use an egg collection stick to observe the oocytes when the eggs are large, relatively uniform, easy to separate from each other, measure the oocyte size must reach an average of 1.3 mm or more, no immature eggs. In recent years, because the male fish is not mature enough, the ratio of male to female should be 2:1 or 3:1.
For spawning fish in a cement tank with a volume of (3x5x1)m=15 m3, the water level is 0.8 -1m deep containing 6 – 10 broodstock with an average weight of 3.5 kg/fish. Cottonfish do not spawn naturally in rafts, so they must be injected with sex hormones to stimulate ovulation. Using HCG hormone to stimulate artificial spawning of fish such as catfish and basa. Using multiple injections of female fish to stimulate the oocytes to absorb the stimulant increases the size of the eggs to the maximum size because this is a Mekong fish with a long migratory path, so they need to be injected several times with a long time to let the oocytes ripen more evenly.
In the first 3 – 5 leading doses using HCG hormone at the same level of 500 IU/kg, the interval between injections is 24 hours. When the eggs have reached the maximum level, the preliminary dose is injected at a dose of 1,000 – 1,500 UI/kg, the interval from dose leading to the preliminary dose is also 24 hours. The final dose is the decisive dose with the use of 5,000 IU, the interval from the preliminary dose to the decisive dose is 8-10 hours. The dose for male fish is 2,000 – 3,000 UI/kg at the same time as the decisive dose for female fish. The duration of hormonal effects from the moment of injection of the decisive dose to ovulation is 9-12 hours.
Check the fish, use a clean towel to dry the whole body, especially the belly of the fish, use your hand to swipe from the back of the fish’s head along the 2 sides of the abdomen to the end point is the genital opening, see the eggs flowing from the fish’s genital opening. female. In male fish, semen also exits from the genital opening which is milky white. Before seeing signs of ovulation, proceed to collect male fish first; Crystals were kept in 0.9% physiological saline. Use a syringe to suck 2 ml of physiological saline, then aspirate 0.5 ml of semen stored at low temperature to prolong the life of sperm.
Then proceed to stroke the eggs, by the dry fertilization method, use chicken feathers to stir the eggs and semen (semen), while stirring the egg and egg mixture, slowly add clean water and create conditions for sperm. active, increasing the probability of fertilizing the egg. Cottonfish is a very weak fish. Therefore, the process of checking maturity as well as selecting broodstock for spawning must be quick and gentle. Only fish are allowed to be put on the test bench and injected with sex hormones right in the water. For female fish, the duration of hormonal effect is 12 hours from the injection of the decisive dose.
After 24 hours of hatching, cotton fry will consume all its yolk sac and begin to eat external food, mainly zooplankton. Breeding cotton wool is divided into 2 stages.
After hatching 24 hours, fry were reared in composite tanks, each tank volume was 1m3, density from 300 fish/m3. Change the water during nursing once a day, each time 20-30% of the water in the tank. For the first 10 days feed Moina or Moina in combination with Artemia’s Nauplius. From day 11 to day 20, feed Moina with 40% protein powder. From day 21 to day 30 feed 40% protein flakes. After 30 days of age, fish reached 0.21 – 0.7 g and 28 – 45 mm long. The survival rate of fish after 30 days of age reached 30.8 – 90.8%.
The fry can be reared in a composite tank with a volume of 1 m3 with different densities such as: 50, 100 or 200 fish/m3. Using a pellet feed with a protein content of 40%, after 60 days of age the fish reached a weight of 3.2 – 3.5 grams/fish, equivalent to a length of 72.2 – 73.3 mm, survival rate of 10. 9 – 98%.
With the amount of information we share. We hope that you can successfully apply it to build a highly profitable fish farming model.