Some notes before entering the 2013 spring-summer shrimp farming season

To make the 2013 spring-summer shrimp farming season highly effective, farmers need to do well some of the following technical steps:

First, prepare the pond before releasing the seeds: this is a very necessary step because if you can create a stable environment, without pathogens in the pond when the weather changes, you can prevent the shrimp from getting sick. Shrimp are bottom-dwelling species, so the pond bottom environment has a great influence on their ability to grow and develop. After each crop, the pond bottom often accumulates layers of waste, contaminated bottom mud, which is a favorable environment for harmful bacteria to develop, creating toxic gases such as NH3, H2S... harmful to farmed shrimp. Farmers need to drain or pump to remove the bottom mud and waste, combine with agricultural lime at a dose of 25-35kg/pond, then plow to mineralize the pond bottom and increase the pH of the bottom layer. If possible, the pond bottom should be exposed for 3-5 days; note that places with thin, black mud and a foul smell need to increase the amount of lime applied.



Applying biofertilizers to shrimp ponds in Quynh Thuan and Quynh Luu communes

After carefully renovating the pond, proceed to collect water and create color. To create water color, farmers should use fertilizers such as: nitrogen - phosphorus mixture with a ratio of 2:1, urea 0.5 - 0.7 kg/sao; NPK (3:5:1) 0.7 - 1.0 kg/sao, mix with water and sprinkle evenly throughout the pond; or you can use algae-inducing fertilizer sold at dealers, dosage according to instructions on the packaging. If using organic fertilizer (cow and buffalo manure), the amount to use is 15 - 20 kg/sao, the fertilizer must be thoroughly composted with 5% lime for 30 days before fertilizing. Normally, to create water color, inorganic fertilizer should be used first for algae to grow quickly (water color), then organic fertilizer should be used to maintain the long-term development of water color.

Next is selecting and releasing the breed. Choosing good breeds is also one of the important factors contributing to the success or failure of the entire farming season. Farmers should choose reputable breeding facilities, the breeds must have a clear origin and must be carefully quarantined before being released into the pond. The criteria for selecting breeds are primarily based on the size of the shrimp. In a source of shrimp with many different sizes, it may not be the source of one mother shrimp but may have many different mother shrimp or different hatching times or poor farming techniques... If the sizes are different, it is very disadvantageous in managing the feeding of the shrimp, they will compete for food with each other. The criteria for having a good breed of shrimp must be uniform, for black tiger shrimp the length is 12 mm and for whiteleg shrimp 9 mm; smaller sized shrimp account for no more than 5% of the shrimp breed.

The best shrimp seeds are ash black in color. Do not use shrimp with many colors or pale white shrimp. These are very weak shrimp, if not taken care of properly, the loss rate will be very high. Other parts such as legs and antennae must be complete and not deformed. When swimming, the tail legs must be fully spread out, which is a healthy shrimp seed. The meat in the abdomen must be full, tight and firm, the outer shell must be smooth and shiny, which is a healthy shrimp.

On the body of the tiger prawn, there are 6 segments in the abdomen, the abdominal segments are long. For whiteleg shrimp, the abdominal segments are rectangular, the head and body are balanced. Experience shows that tiger prawns with longer abdominal segments grow faster than those with shorter abdominal segments. If you observe carefully and see if there are any foreign objects attached, you should not use them, because later they will not be able to molt and will die. Take 200 shrimp randomly from the school and put them in a basin of clear water. Then, use your hand to stir around the edge of the basin. If you see more than 10 shrimp floating with the water or being swept to the bottom of the basin, it is a weak shrimp...

In addition, farmers can evaluate the health of shrimp larvae by shock method with Formalin concentration of 2-2.5ml/10 liters for 30 minutes. If the shrimp mortality rate is not more than 5%, the shrimp population is good. Or by suddenly lowering the salinity, take 100-150 P15 shrimp and put them in a container containing 1 liter of nursery water. If the water in the shrimp nursery tank has a salinity of over 20%o, add fresh water to suddenly reduce the salinity by half (ie add one liter of water in the shrimp nursery tank and 1 liter of fresh water). If the salinity is lower than 15%o, the shrimp can be put directly into the freshwater environment. After 2 hours of observation, if the shrimp mortality rate is less than 5%, the shrimp population is good. In particular, shrimp larvae must be tested by the competent authority for parasitic diseases, MBV, taura syndrome...

Regarding the farming season, farmers should follow the seasonal calendar of the Department of Agriculture and Rural Development, in which the main crop starts from April to June 30 (for whiteleg shrimp) and from April to May 30 (for black tiger shrimp). After the main crop, farming areas with good infrastructure conditions and a stable water environment can release a secondary crop, from September 20 to October 30 (for whiteleg shrimp). Black tiger shrimp are not released for the secondary crop, the shrimp farming density depends on pond conditions, experience and financial capacity, but to be effective, when intensively raising black tiger shrimp, farmers should release 15-20 shrimp/m2, Poslavar 15 size and 80-100 white tiger shrimp/m2, Poslavar 12 size.

Finally, the care and management stage: in the first 1-2 months, it is necessary to take care of feeding carefully to keep the shrimp healthy; keep the pond environment always stable, maintain fertilization to create a clear water color of 30-35 cm, the best pond water color is light brown or young banana green, especially do not let the phenomenon of water discoloration, algae die. In case of algae die, it is necessary to treat immediately by using Zeolite or biological products to limit shrimp death.

Tran Trung Thanh (Nghe An Agricultural Extension Center)