Typically, prawn farmers in Chanthaburi province stock their ponds in January or February, with the intention of harvesting that crop just before April’s Songkran holiday. This year, however, things have turned out differently.
“Only 30% of all farmers have started stalking,” says Chakarin Pecharoen, Chairman of the Chantaburi Shrimp Farmers Club. “[The last quarter of 2012] netted a decrease of around 20-to-30%. But I have a deep feeling that the production in this first quarter might turn out to be something very horrible.”
Many shrimp ponds in Chanthaburi and throughout Thailand remain bone dry at this late point in the season because of fears about a scourge affecting crustaceans region-wide. EMS (Early Mortality Syndrome) is a phenomenon as mysterious as it is deadly and in the past three years, it has threatened to undermine Asia’s commercial shrimping industry.
Reports of EMS first surfaced in 2009 in China, where farmers noticed that their prawns had begun dying en masse, without any identifiable cause.
In the commercial shrimping industry, where occasional epidemics are par for the course, a Chinese die-off failed to qualify as news. However, as the months proceeded and dead shrimp continued to pile up, the statistics became too massive to ignore.
By 2011, shrimp farms in China’s Hainan, Guangdong, Fujian and Guangxi provinces were suffering losses as great as 80%. Without a specific pathogen to blame, farmers christened the disease according to its immediate effect – Early Mortality Syndrome.
From China, EMS made the leap to Vietnam and to Malaysia, where it left similarly massive swathes of devastation. In 2011 and 2012, EMS wreaked havoc on Vietnam’s shrimping industry. The province of Tra Vinh saw 330 million shrimp die in the month of June 2011 alone. Aquaculture news outlet The Fish Site used terms like “widespread devastation” in describing the outbreak.
Malaysia, where EMS first emerged in 2010, displayed a similar pattern. Between 2010 and 2011, its commercial prawn industry demonstrated a year-on-year decrease in production of roughly 42%.
“It’s a huge phenomenon,” says Daniel Gruenberg, CEO of Sea Garden Foods, an aquaculture and shrimp farming company in Chonburi province. “Just to give you a measuring stick, I had some friends that sell [prawn feed] and if they look at their year-on-year feed sales they’re down 70% to 80%. It’s massive.”
In Thailand, EMS has not racked up a death toll as large as those seen in China and Vietnam. However, since the phenomenon’s 2011 appearance in the Kingdom, its effect has been drastic, and increasingly difficult to ignore.
EMS first arrived in the eastern provinces of Chanthaburi and Rayong, where it has caused year-on-year decreases in prawn production as high as 40% by some accounts.
Even worse than the EMS itself is the panic it has engendered among local farmers. Gruenberg speculates that as many as 80% of the shrimp farmers in eastern Thailand have chosen to leave their ponds dry, rather than risk their capital by stocking shrimp that may or may not survive to maturity.
Though his estimate employs figures more cautious than Gruenberg’s, Dr. Putth Songsangjinda, Director of the Marine Shrimp Culture Research and Development Institute, concurs.
“The real problem is panic among shrimp farmers,” he says. “With
farmers delaying their stocking, it could adversely affect Thailand’s whole
shrimp production.”
For Thailand’s billion-dollar-plus yearly shrimping industry, these drops in production could prove catastrophic. The country’s shrimp exports are already in a less-than-ideal state, having suffered steady declines since their peak in 2000. With a 26.7% year-on-year drop in production between 2011 and 2012, the industry is ill positioned to withstand further shocks.
Though contained for the most part to the east of the country, outbreaks of EMS have begun to show up in Thailand’s southern provinces as well. So far, no one has conducted an extensive economic study of EMS’s impact on the Asian prawn fishery, but it numbers in the millions of US dollars, if not billions.
With so much money on the line, both shrimp farmers and academic researchers have entered a race to find the phenomenon’s cause, but so far, it remains an enigma. Authorities can’t even agree on whether or not it’s a disease. Dr. Putth hesitated to call EMS an epidemic because, in order for something to earn that status, its cause must be known. In the case of EMS, all scientists and farmers have to go off of are its effects.
EMS causes a prawn’s hepatopancreas (essentially a liver and pancreas combined) to malfunction. This in turn interferes with the animal’s ability to digest food, thereby weakening it and leaving it susceptible to disease. (The technical name for EMS is Acute Hepatopancreatic Necrosis Syndrome (AHPNS), though EMS has entered more common usage, owing at least in part to its brevity.)
Prawns typically run afoul of EMS while in the post-larval phase, which in general lasts for the first 35 days after they are planted in a shrimp pond. Though academics studying the phenomenon remain skeptical as to whether or not EMS can also affect mature shrimp, farmers such as Gruenberg insist that it can and does.
After at first assuming that a virus had caused EMS, researchers soon widened their range of possible culprits to include genetic abnormalities, bacterial infections, toxins and shifting environmental conditions.
A March 2013 disease advisory for EMS released by the Network of Aquaculture Centres in Asia-Pacific summarized the situation bluntly: “So far, no causative agent has yet been found and the disease is still considered idiopathic.”
Gruenberg believes that he may have found the cause, but his experiments are still in the initial stages and he prefaces his description of them with a caveat that they at best constitute a “working hypothesis.”
He believes that selective breeding in one of the most widely farmed specie of shrimp – L. vannamei – has led to the current catastrophe. By selecting shrimp for fast growth, Gruenberg contends that breeders have inadvertently selected for weak immune systems as well.
With inadequate immune systems (“like an AIDS patient,” says Gruenberg) these shrimp become susceptible to infection from a parasite known as Gregarine, which acts somewhat like a crustacean version of malaria.
Gruenberg and his team have set up a series of experimental shrimp ponds in which they are trying to save shrimp from EMS by feeding them copepods – a nutrient-dense zooplankton that can help compensate for the prawns’ ravaged digestive capabilities and weakened immune systems.
So far, Gruenberg’s experiments have turned out well, but he has yet to apply them on a scale large enough for the victory to qualify as decisive.
“Normally if a pond starts getting EMS, within a few weeks you’re going to be getting 100% mortality,” he says, “but we were able to save about 50% of the prawns at [the experimental] pond. So that opened our minds to nutrition as one possible solution.”
In the mean time, Southeast Asia’s prawn farmers have little choice but to sit by and anxiously await a cure.
When asked about how bad things could get if the EMS outbreak continues, Chakarin, Chairman of Chanthaburi Shrimp Farmers Club, responds simply, “I dare not say.”
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