Breeding is an important factor that determines over 50% of the success of the crop. Therefore, understanding the methods of selecting stocking is essential.
Seed quality plays an important role in the success of the crop
Sensory evaluation method: Shrimp seed has uniform size, the number of shrimp difference does not exceed 5%. The length of shrimp body is greater than 12 mm (tiger shrimp), 10 mm (white leg shrimp). The color of the shrimp is bright, the shell is thin, the color is black to black, the body is balanced, the tail is spread out as a good breed. Shrimp breeds are flexible, healthy, evenly distributed in tanks, elongated shape, intestines are full of food (good ability to catch prey).
Using your hand to lightly tap into a shrimp container, if the shrimp reacts quickly, the shrimp will be strong. Unwell shrimp will be lethargic, unresponsive and the body will curve when swimming. Or drop shrimp seed into brass, stirring with hands, healthy shrimp often swim upstream or stick around the walls, weak shrimp gather in the middle.
Observation method on microscopy: Healthy shrimp, pigment cells (in the abdomen) often appear as small spots with star shape. Weak shrimp, chromatophores often spread into lines that line each other below the abdomen. Shrimps have the abdomen as long as possible and the shrimps grow fast. Shrimp with a V-shaped tail and close angle of two antennae like the V-corner are healthy shrimp. There are no fungi, bacteria or protozoa that attach to the legs, abdomen, tail, shell and shrimp. These groups will interfere with the respiration and shedding of shrimp.
Shocking method: This method evaluates the tolerance and health status of shrimp seed.
Shocking salinity: Sampling about 100 – 200 postlarvae, if the water in the nursery is over 20 ppt, saline water and fresh water will be mixed at a ratio of 1: 1, if the salinity level is lower than 20 ppt can feed shrimp directly in freshwater environment. After 2 hours, if the shrimp mortality rate is below 5%, it is a good shrimp herd.
Shocking Formol: Take about 10 liters of water in a nursery tank, prepare a Formol solution of 200 ppm (2 cc / 10 liters of water), and add about 100 postlarvae. After 2 hours, if the shrimp dies no more than 5%, the shrimp will meet the requirement.
PCR method: This method evaluates whether or not the shrimp infected or not infected with some viral diseases such as yellow head (YHV), white spot (WSSV), (MBV) … Made by the aquatic disease laboratory. Before choosing to buy breeds, farmers need to take samples for testing.
How to drop
There are two ways to safely stock shrimp, namely:
Method 1: Newly transported shrimp bags drop on the pond surface for about 15 – 30 minutes to balance the inside and outside temperature. Then open the mouth of the bag, throw from the outside of the pond into the bag, then gradually open the cover to let the shrimp swim out. When stocking, avoid wading into the pond to make pond water turbid.
Method 2: Prepare some large brass about 20 liters and aeration machine. Pour the shrimp bag into about 10,000 pieces / brass plate and aerate the air. Add water to pond water little by little to adjust shrimp gradually. After about 15 – 30 minutes tilting the brass so that the shrimp swim slowly. Some signs to identify healthy shrimp are adaptation to the water environment when pure shrimp in the brass, no or little shrimp die. Shrimp swim flexibly, clinging to the walls of brass. Healthy shrimps after being released in a sinking pond are not floating on the water.
Shrimp should be purchased at a facility that has a license to provide shrimp seed (shrimp has passed quarantine and agreed for distribution by specialized agencies).
Should choose breeding stock from a mother, to avoid the situation of many breeding shrimp in the same tank, the quality of larvae will be uneven. Choose to breed shrimp seed from reputable and brand production facilities, with shrimp herd parents ensure quality according to regulations; must check some specific diseases such as MBV, white spot, yellow head, taura, pancreatic liver necrosis … (with quarantine paper) on shrimp.
In addition to the method of mechanical inspection, sensory evaluation of production facilities must be conducted before choosing to buy seeds: The hatchery must be clean, airy, full of equipment and infrastructure for seed production; production equipment must be treated with specified disinfecting chemicals and dried; check whether the tanks have dead shrimp; aeration, whether the tank is clean or not; Do you use antibiotics and chemicals in your aquarium?
Breeding should be done at cool weather. Balancing salinity before transport to have similar salinity and temperature must balance between two environments. Shrimp seed heads in the wind direction to disperse shrimp throughout the pond.
Cre: Thủy sản Viêt Nam