New direction in shrimp seed production
Producing shrimp seed by cutting the eyestalk will reduce the number of spawnings and the quality of shrimp. Applying the method of producing natural shrimp without cutting the eyestalk will solve the current difficult problem of shrimp seed, creating a uniform, disease-free shrimp seed.
Change traditional methods
Most shrimp seed production today uses the traditional method of cutting the eyestalk of the mother shrimp to stimulate the molting process, increase the ability to mature sexually and speed up the egg-laying process of the shrimp. The reason for using this method is because the eyestalk of shrimp (both male and female shrimp) contains the X-organ complex (nodal gland), the X-organ directly controls the synthesis of the hormone that inhibits gonadal development (GIH) and the hormone that inhibits molting (MIH). Therefore, cutting the eyestalk will remove some of the X-organ complex, thereby reducing the inhibitory factor on the development of the gonads (GIH). Besides the advantages, shrimp with eyestalk cut have some limitations: They only spawn 3-5 times, after which their reproductive life ends; the quality of the next spawning gradually decreases.
Due to the characteristics of black tiger shrimp with closed Thelycum, when cutting the female shrimp's eyestalk, it will molt, the reproductive organs will soften, from which the male shrimp can easily attach the sperm sac when mating. As for white leg shrimp (TTCT), due to the open Thelycum, reproduction is carried out smoothly even without molt. Based on that characteristic, the production of TTCT breed by natural farming has been successful and achieved good results. This method is a synchronous chain from selecting parent shrimp with origin, disease-free and investing in applying comprehensive technical measures to create TTCT breed to limit infection with white spot, Taura, yellow head, muscle necrosis, hepatopancreatic necrosis. Therefore, the resistance, survival rate, and growth rate of shrimp are also higher than the eye cutting method.
Application in shrimp seed production
This natural, non-ablated TTCT seed production process involves selecting Hawaiian parent shrimp weighing over 45g/male and 50g/female. Domestication and breeding of parent shrimp is a very important stage, requiring adequate nutrition and control of environmental parameters under appropriate conditions to help the shrimp mature naturally. Managing environmental parameters (temperature, salinity) and using appropriate nutrition are considered key factors in the process, aiming to achieve consistent, stable seed quality and have many advantages over traditional methods.
In fact, when shrimp are in the wild without their eyestalks cut off, they can lay eggs more often over a long period of time, producing more baby shrimp. Therefore, people have studied how to stimulate shrimp to lay eggs without cutting their eyes. In the world, serotonin injections have been applied to female shrimp, and the rate of first-time spawning was 35.4%, six times higher than the control. The rate of shrimp laying eggs the second time was 6.7%. In general, the number of shrimp that laid eggs stimulated by serotonin was seven times higher than the control. The rate of shrimp that laid eggs by serotonin injection was lower than that of shrimp that had their eyestalks cut off. However, after a series of spawnings, the number of shrimp that had their eyestalks cut off could no longer be used to produce shrimp seeds. Meanwhile, shrimp that laid eggs by serotonin continued to spawn because they were not damaged, thus prolonging the reproductive life of the shrimp.
After 1-2 months of active rearing, mature female shrimp will be released into the male shrimp tank for self-mating, then transfer the female shrimp to the spawning tank. At this time, it is necessary to ensure that the spawning tank has suitable temperature conditions, is quiet, and has no light. After 36-40 hours, collect the Nauplius and transfer to the nursery to continue rearing to Postlarvae.
This method has many advantages: Because the eye stalk is not cut, it does not cause damage to the mother shrimp, and does not take time to care for the mother shrimp to recover like when the eye is cut. The number of Nauplius obtained is greater than 200 Nauplius/female, the transition time from Nauplius to Postlarvae 12 is 18 - 19 days, 1 - 2 days shorter than the eye stalk cutting method and the length of Pl 8 (Postlarvae 8) is equivalent to Pl 10 of the eye cutting method. The shrimp seed has uniform quality, no deformities, and is healthy. In the face of the floating of shrimp seeds and rampant diseases, this method is considered a good signal to help the Vietnamese shrimp industry.
Vietnam Seafood Source - LY
