By: Ph.D. Stephen G. Newman*
Many ask why Ecuador is able to produce so much shrimp and why are they able to produce them so inexpensively? While questions of this nature rarely have a single simple explanation, it is more than likely that most of them are the result of the adoption of technology. Some are using the term technification to describe this. Technification can lead to increases in productivity, although it has practical limits.
Ecuador is the world’s leading exporter of farmed shrimp with exports in 2022 of over 1 million MTs. Through April 2023, the trend is increased exports. Ecuador appears to be set for a 1.2 – 1.3 million MT year, provided that the market continues to remain strong.
Many ask why is Ecuador able to produce so much shrimp and why are they able to produce them so inexpensively? While questions of this nature rarely have a single simple explanation, it is more than likely that most of them are the result of the adoption of technology.
Some are using the term technification to describe this. Technification can lead to increases in productivity, although it has practical limits.
The historical production paradigm in Ecuador has been low stocking densities in large ponds with modest water exchange rates, little to no supplemental aeration and feeding by casting feed or the use of trays. Some microbial tools have been used to treat the sediments prior to stocking.
Ecuador lost almost 2/3rds of their farmed shrimp production when the White Spot Syndrome Virus (WSSV) first hit in 1999/2000. It took the better part of seven years after that before they were producing at their pre-WSSV production levels.
Since then, the rate of production has increased year after year in small increments until around 2016, when the growth rate began to accelerate (Figure 1). This has made Ecuador the world’s largest exporter of farmed shrimp. What are some of the reasons for this growth and what are the risks?
The trendline for the data above, MTs per year of shrimp produced, shows slow but steady growth with a gradually increasing rate of expansion, with production more than doubling from 2018 to the present. Along with this growth, there has been a change in the production model.
At this point, it is relevant to discuss another aspect of the production in Ecuador. The standard in terrestrial agriculture and indeed in most aquatic production is to prevent animals from being exposed to obligate pathogens. Opportunistic pathogens are unavoidable, and the use of best management practices is typically the best approach towards limiting their impact.
Exclusion is part of this, where practical. The idea is to reduce the overall susceptibility of the population via genetics, density reduction, nutrition, and stress reduction. For shrimp it is challenging to get rid of many pathogens simply because of the nature of the aquatic environment.
“Disease is controlled by limiting exposure and minimizing the factors that determine susceptibility. Ecuador took a different approach.”
Seeing that shrimp are different than other farmed animals, many decided that it made more sense not to control the levels of pathogens in the environment but instead allow them to impact the population. The theory was that the survivors would be resistant or tolerant to obligate pathogens.
This was done using the existing paradigm, which was relatively low density, borderline extensive grow out. Shrimp were stocked at around 10 (+/- 5) animals per square meter and 60% of these survived to harvest. The largest animals were selected and used as the source of the next generation´s animals.
This was repeated year after year. In 2023, this stocking number might average twice this (20 +/- 5). Moving much further than this could be problematic. Known as all pathogen exposure (APE), some attribute Ecuador’s current success to this.
“Yet if one takes these animals and exposes them to obligate pathogens under controlled conditions in the lab, they succumb. I have witnessed this in the field.”
Ecuador can get (relatively) cold and there are times and places where the temperatures are too low for the ideal production of farmed shrimp.
The shrimp grow poorly and/or have other issues and challenges. A group of animals being cultured under a plastic roof were culled in order to reduce the density in the pond and placed into cooler water. They broke with WSSV, and all died. What APE has done is ensure that obligate pathogens are endemic.
If there was a very cold period of weather the disease and the opportunistic bacteria that thrive when animals are weakened by it would likely wreak havoc. Not only that, because no effort has been made to keep any pathogens out of the system despite claims that no shrimp from outside of Ecuador have been brought in, animals have found their way into Ecuador.
“Additionally wild animals are still being used to try and limit the inbing that is a result of their genetics programs. There are likely pathogens present in these shrimp that are not characterized and are impacting animals.”
The vibrio that causes acute hepatopancreatic necrosis syndrome (AHPNS) is present as is Enterocytozoon hepatopenaei (EHP) (these are ubiquitous with very few countries not having them) and possibly any number of viruses, including several uncharacterized noda viruses among others.
There are no stable immortal cell lines that allow the culturing of viruses of shrimp. Primary cell lines that die out after a few passages are all that exist. Histopathology is the primary tool for determining whether uncharacterized viral pathogens are present.
Viruses invade cells and cause changes in the cells as the virus replicates. These are readily apparent using the right stains and looking at the targeted tissues. All animals that are a part of thriving dynamic populations exchange microbial flora. Major sources of disease in farmed shrimp globally are pathogens that move from broodstock to the PLs and onto the farm.
If Ecuador were strictly APE and no measures were taken to minimize this, some pathogens such as the vibrio that causes the toxicosis AHPNS would impact PLs and animals that are stocked would still be succumbing from this toxicosis or if the exposure is low and chronic, growth and overall animal fitness in grow out would be affected.
Some proactive measures are probably being taken. When animal densities increase either as a result of higher stocking densities or simply due to animals growing to much larger sizes than has been the historic norm, as a result of genetic selection, the levels of stress that the animals are under increase as well as the pathogen pressure.
Higher levels of pathogens increase the probability of pathogens moving between animals. This increases the likelihood of acute disease. Opportunistic pathogens also come into play as in many instances what is killing the shrimp is not an obligate pathogen.
“They are merely setting the stage. There is compelling evidence that many shrimp that succumb to WSSV are dying from secondary infections. The virus weakens them, and secondary pathogens kill them.”
So, what is the bottom line? Ecuador’s success is the result of technification. While APE might play some role, it has left Ecuador exposed. The evolutionary success of shrimp is due to a variety of reasons. A property that is common to most eukaryotes is the ability to incorporate pieces of viral nucleic acids into their genome and use it to create what is known as RNA interference (RNAi).
This acts by blocking the ability of the specific virus to replicate. How long it lasts, how effective it is, what pathogens it works on, etc. remain to be determined. These sequences are thought to be passed to the next generation although it is likely more complex than this or we would already have animals that were immune to infection at high levels.
The only way to actually determine if this is present in farmed stocks requires challenging animals in the lab along with appropriate controls. Survival in ponds can be due to many things.
“What about those viruses like WSSV that are essentially dormant until the temperatures drop? We know that WSSV can start a cascade that leads to death even in animals that have been part of the APE program since its inception.”
It remains to be seen if this theory is correct. Ecuador may find it challenging to keep expanding low-cost production if technification is being used to intensify it beyond a certain point. Performance in the field is of course impacted by many variables and consistency can be elusive.
Technology that allows farms to produce 50 or more MTS per ha per year, while not the norm, nonetheless exists in SE Asia and sporadically in the Americas.
These are in small ponds, rarely a ha in size. Most are lined and heavily aerated. Automatic feeders are in use although some hand feeding is also common. Survivals rates can be higher than 90% (based on accurate stocking numbers). Ecuador has never been about producing high yields. It has always been about having a huge amount of developed acreage where a few MTs a year per ha is profitable.
Shifting to a high-density production paradigm requires the right animals and a clean production environment. Keeping animals free of pathogens maximizes the likelihood that the environment will be largely free of them. Shrimp can grow without the pressure of pathogens impacting their growth rates allowing them to realize their genetic potential.
There are limits to the carrying capacity of given production environments. Exceeding the carrying capacity results in stress and invariably, if persistent, disease problems.
This is the history of shrimp farming. Exactly what factors in the paradigm impact the carrying capacity is complex. Waves of deadly diseases move through the global industry regularly and the number one reason shrimp farmers lose money is disease.
There is no indication that this is changing nor is there any real reason to believe that it will. While some efforts are made, such as restricting the flow of broodstock and imports of potential vectors, there are lots of loopholes. Plugging these in is not easy.
“Recent studies have shown that there are likely many viruses present in the marine environment in other invertebrates such as crabs that can be in close contact with farmed shrimp and could mutate and infect shrimp. One cannot help but conclude that caution is warranted.”
If attempts to raise stocking densities are resulting in high mortality, even sporadically, these should be discouraged. Even in those SE Asian paradigms with small, lined ponds, over feeding can set off a cascade of production challenges. The risks are real. Most knowledgeable animal health professionals who understand this will tell you that it is not a matter of if but when.
How hard it hurts could (much as with WSSV) determine the short-term future of the industry. It has shown itself to be resilient when many others have not. Production in Thailand, once the world’s leader, dropped post WSSV and never returned to earlier levels.
Ecuador can and will continue to produce more shrimp. Technification/intensification will ensure this. The use of automatic feeders has dropped feed conversion ratios, resulting in less waste and a lower cost of production. Aerators that ensure that dissolved oxygen levels are almost always in the near saturation range minimize stress.
“The use of bioremediation/bioaugmentation has reduced the presence of accumulated waste and the amount of anaerobic pond bottoms that are generating hydrogen sulfide and methane, which are both detrimental and stressful.”
The question remains as to whether the current trend is sustainable and what the impact of APE is on the carrying capacity at higher production densities. It is important to learn from our mistakes and those of others.
There are practical limits to what the environment can tolerate before feedback damages our ability to continue in the same manner. With intensification there are still practical limits. Long held experience shows that excess feed levels 90 kg/ha/day can be detrimental.
The challenge is to find the sweet spot. The amount of biomass that is sustainable at a given density will not set off a cascade of events that result in a disease outbreak. Ecuador is up for the challenge and one can expect that they will continue to increase production as long as the market for shrimp allows.
Stephen G. Newman has a bachelor’s degree from the University of Maryland in Conservation and Resource Management (ecology) and a Ph.D. from the University of Miami, in Marine Microbiology.
He has over 40 years of experience working within a range of topics and approaches on aquaculture such as water quality, animal health, biosecurity with special focus on shrimp and salmonids.
He founded Aquaintech in 1996 and continues to be CEO of this company to the present day.
It is heavily focused on providing consulting services around the world on microbial technologies and biosecurity issues.