PLs ready for stocking in nursery ponds, biofloc tanks, or production ponds. Note the uniform size.
Setting aside the details for now about actually building a farm and all of the required infrastructure, the process is as follows.
One must start with a source of baby shrimp. These are called post larval shrimp or PLs for short. Shrimp go through a series of larval stages (by molting) after the eggs hatch before they molt into PLs. Shrimp are invertebrates with their skeletons, consisting of a polymer called chitin, on the outside of their bodies. They must shed or molt this to grow. As the post larval shrimp molt (typically daily in hatchery tanks) they are designated by the days post their molt into PLs from pre-larval stages. Secondary gill development, essential for the ability to osmoregulate, is monitored and typically when the animals have the required level of development they are ready for stocking into ponds. This usually ranges from PL8 on up. The photo above shows high quality PLs ready for stocking.
There are many things that can impact what happens on the farm. Not all of these come from the farm. Many originate from the hatchery and some from the broodstock.
Broodstock
Are essential to being able to consistently produce strong, healthy, rapidly growing shrimp at all stages of growth. Genetic selection can dramatically impact growth given the right environment.
The movement of pathogens between shrimp producing areas and countries is often a result of moving infected broodstock and/or nauplii/PLs produced from them. This is perhaps the single greatest risk to the stability and sustainability of shrimp farming. Disease is natural and in high stress production environments where pathogens are brought into the production environment as a result of inadequate biosecurity the consequences can be dire.
Wild broodstock are still used in some parts of the world despite the practice being widely acknowledged as not being sustainable, carrying with it a high risk of disease and in general a poor practice. Most of the wild broodstock in use are P. monodon. Without testing of each individual animal, testing the appropriate tissues, stressing animals to express viral pathogens that may have gone dormant and constantly examining dead and dying broodstock for evidence of pathology that could be explained by the presence of as of yet uncharacterized pathogens, the chances that there will not be problems with this approach are close to zero. It is inevitable.
Today, most farmed shrimp are produced from captive broodstock. These fall into several categories ranging from the highly biosecure to the flagrantly non-biosecure. Biosecure stocks are necessary to minimize the potential for disease problems on the farm. This is actually an easy way to make money as the demand can readily exceed supplies at certain times of the year and in areas where stocking is being done all at once, creating a huge demand for PLs in a very short period of time. This lure has attracted many companies that should not be in this business.
There are genetically improved animals P. monodon and L. vannamei commercially available Most of the earlier programs focused on a conventional approach. Survivors from ponds were selected based on phenotypes that were deemed to be important. This could be as simple as culling the largest animals at harvest and using them for broodstock. Even today there are some programs that cling to this approach insisting that that animals at harvest have survived disease outbreaks because they are better in some way, ignoring the role of chance in survival. Genetics programs range from the very small to the huge. The safest source of broodstock is from the few companies that have nucleus breeding facilities.
This means that the animals have been held in isolated indoor, bio-secure environments for multiple generations. They are specific pathogen free (SPF) and in some cases have shown tolerance against some diseases (SPT). While some companies claim animals are resistant this is not usually accurate. Not all lab results move well to the field. Few strains are not susceptible to pathogens at some levels and the role(s) of stressors in stress filled production systems is not widely appreciated. Field data is not a good measure of susceptibility. Controlled lab studies are needed to verify that the animals are showing some degree of tolerance to the pathogen(s) of interest. Unfortunately this does not mean that in the field the animals will be any less likely to fall ill. Disease is often multifactorial rarely without more than one pathogen present and not always as simple as a pathogen simply being in the production system.
When you use broodstock that are not from nuclear breeding centers and that have been produced outdoors, regardless of test results, they can no longer be considered SPF. Some consider these animals to be "High Health" as a result of the source and no lengthy exposure Unfortunately far too many farmers fall victim to forged certificates or simply do not understand what this really means. They buy based on price and relationships not on science based assurances of quality. PCR results for some viruses are not reliable.
One must start with a source of baby shrimp. These are called post larval shrimp or PLs for short. Shrimp go through a series of larval stages (by molting) after the eggs hatch before they molt into PLs. Shrimp are invertebrates with their skeletons, consisting of a polymer called chitin, on the outside of their bodies. They must shed or molt this to grow. As the post larval shrimp molt (typically daily in hatchery tanks) they are designated by the days post their molt into PLs from pre-larval stages. Secondary gill development, essential for the ability to osmoregulate, is monitored and typically when the animals have the required level of development they are ready for stocking into ponds. This usually ranges from PL8 on up. The photo above shows high quality PLs ready for stocking.
There are many things that can impact what happens on the farm. Not all of these come from the farm. Many originate from the hatchery and some from the broodstock.
Broodstock
Are essential to being able to consistently produce strong, healthy, rapidly growing shrimp at all stages of growth. Genetic selection can dramatically impact growth given the right environment.
The movement of pathogens between shrimp producing areas and countries is often a result of moving infected broodstock and/or nauplii/PLs produced from them. This is perhaps the single greatest risk to the stability and sustainability of shrimp farming. Disease is natural and in high stress production environments where pathogens are brought into the production environment as a result of inadequate biosecurity the consequences can be dire.
Wild broodstock are still used in some parts of the world despite the practice being widely acknowledged as not being sustainable, carrying with it a high risk of disease and in general a poor practice. Most of the wild broodstock in use are P. monodon. Without testing of each individual animal, testing the appropriate tissues, stressing animals to express viral pathogens that may have gone dormant and constantly examining dead and dying broodstock for evidence of pathology that could be explained by the presence of as of yet uncharacterized pathogens, the chances that there will not be problems with this approach are close to zero. It is inevitable.
Today, most farmed shrimp are produced from captive broodstock. These fall into several categories ranging from the highly biosecure to the flagrantly non-biosecure. Biosecure stocks are necessary to minimize the potential for disease problems on the farm. This is actually an easy way to make money as the demand can readily exceed supplies at certain times of the year and in areas where stocking is being done all at once, creating a huge demand for PLs in a very short period of time. This lure has attracted many companies that should not be in this business.
There are genetically improved animals P. monodon and L. vannamei commercially available Most of the earlier programs focused on a conventional approach. Survivors from ponds were selected based on phenotypes that were deemed to be important. This could be as simple as culling the largest animals at harvest and using them for broodstock. Even today there are some programs that cling to this approach insisting that that animals at harvest have survived disease outbreaks because they are better in some way, ignoring the role of chance in survival. Genetics programs range from the very small to the huge. The safest source of broodstock is from the few companies that have nucleus breeding facilities.
This means that the animals have been held in isolated indoor, bio-secure environments for multiple generations. They are specific pathogen free (SPF) and in some cases have shown tolerance against some diseases (SPT). While some companies claim animals are resistant this is not usually accurate. Not all lab results move well to the field. Few strains are not susceptible to pathogens at some levels and the role(s) of stressors in stress filled production systems is not widely appreciated. Field data is not a good measure of susceptibility. Controlled lab studies are needed to verify that the animals are showing some degree of tolerance to the pathogen(s) of interest. Unfortunately this does not mean that in the field the animals will be any less likely to fall ill. Disease is often multifactorial rarely without more than one pathogen present and not always as simple as a pathogen simply being in the production system.
When you use broodstock that are not from nuclear breeding centers and that have been produced outdoors, regardless of test results, they can no longer be considered SPF. Some consider these animals to be "High Health" as a result of the source and no lengthy exposure Unfortunately far too many farmers fall victim to forged certificates or simply do not understand what this really means. They buy based on price and relationships not on science based assurances of quality. PCR results for some viruses are not reliable.