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In November 2011, a devastating disease appeared in Thailand’s shrimp farms. Time and time again, farmers dipped their nets into aquaculture ponds and pulled out limp, lifeless shrimp, often just days after the ponds had been stocked. This problem—first referred to as early mortality syndrome (EMS)—hit the world’s shrimp supply hard. Before EMS hit, Thailand was the world’s largest exporter of farmed shrimp. With the losses, shrimp prices in places like the United States and Europe spiked, restaurants took shrimp specials off their menus, and countries that typically bought shrimp from Thailand looked elsewhere.
Roughly a year and a half later, a research team led by shrimp pathologist Donald Lightner identified the cause of the deaths: an infection by the bacterium Vibrio parahaemolyticus. Renamed acute hepatopancreatic necrosis disease, or AHPND (pronounced like “happened” without the h), the disease hampers the shrimp’s hepatopancreas—a dark, pea-sized organ that functions as both a liver and a pancreas. The disease first emerged in southern China in 2010 and moved through Vietnam and Malaysia before it reached Thailand.
In Thailand, AHPND took no prisoners: nearly all shrimp farms were affected. Many shrimp farmers ignored experts’ recommendations to disinfect their ponds and source shrimp from different suppliers. In a 2013 report, the Global Aquaculture Alliance estimated AHPND caused annual global losses of more than US $1-billion.
While many shrimp farmers struggled to pull a profit out of increasingly beleaguered stocks, Chaiwairuth Arunsopha, the owner of Thongchai shrimp farm in eastern Thailand, started designing a new way to farm shrimp.
Arunsopha has an open but firm demeanor and approaches shrimp farming with a rather Zen attitude. “[Early mortality syndrome] isn’t going to go away, and it looks like we will have to live with it,” he says. “The point now isn’t to kill EMS but to find a more green, sustainable way to grow our shrimp.”
Arunsopha is no scientist, but he grew up around shrimp, and his approach—instilled by his father who worked in the shrimp business—is that you learn by doing. This philosophy has driven him to treat his farm like a research base. In 2014, Arunsopha elicited the help of scientist Paisarn Wong-wassana, and they dedicated the entire year to restructuring the shrimp farm, transforming his ponds that used to solely grow shrimp into an experimental closed system.
Arunsopha’s farm has 33 ponds of four different types, all of which work together. The first type of pond has aerators to keep the water oxygenated, shrimp moving, and sediment concentrated in the center of the pond. The dirty water from the first type of pond is suctioned into the second type, which contains tilapia. The tilapia feed on the waste from the first pond and filter the water. Tilapia flow from their reservoir into a third pond—which contains barramundi, or sea bass, to control the tilapia population—by gravity. Finally, in the fourth pond, minerals and nutrients are added to the clean, filtered water before it is returned to the first pond.
On Arunsopha’s farm, this closed-loop system improved shrimp survival rates from a baseline of between 30 to 50 percent all the way up to 90 percent. Last year, more than 1,000 people from the Charoen Pokpand group, Thailand’s largest producer of animal feed and livestock, came to learn his methods.
In regard to controlling AHPND, Peter de Schryver, a microbial ecologist at Ghent University in Belgium, believes that a closed system is “the future, at least from an environmental perspective.”
“In nature, everything is in perfect balance: the diversity of species living together in the appropriate densities, surrounded by large volumes of water. All these factors are artificially manipulated in aquaculture to increase culture output, but, evidently, at a cost,” he says. De Schryver believes that the key to controlling AHPND involves maximizing disease resistance of the shrimp and minimizing the chances for the pathogen to develop inside shrimp farms by using closed systems. Growing tilapia alongside shrimp has been shown to reduce the incidence of disease outbreaks. However, a closed system is not necessarily a cure-all for AHPND. If not properly controlled and cleaned, these systems could propagate issues such as poor water quality or the accumulation of waste.
Despite his successes, Arunsopha’s experimentation has not entirely freed him from the threat of AHPND. In an email toward the end of January, he told me: “As I’m typing this, EMS is hitting again.”