EMS - How Early Mortality Syndrome Changed Shrimp Farming
In a world with an ever-increasing population, shrimp farmers across the globe have begun to abandon traditional poly-culture farms and turn towards increasingly technologically advanced monoculture and intensive farms in order to meet the world’s growing food demands. Lucrative, efficient and necessary, these farms are a huge step in optimizing the shrimp industry, where farmed shrimp accounts for 55% of the shrimp produced globally. However, as any seasoned farmer or population dynamics biologist would know, when population is increased without adequate increases in habitat area, certain risks emerge and the results can be catastrophic. Enter EMS, the disease that has already drastically altered the face of shrimp farming.
Picture it: Southern China, 2009. A shrimp farmer notices a lethargy move across his juvenile shrimp and before the week is out more than half of his stock is lost. The pattern follows throughout his neighbors’ ponds and the entire Chinese shrimp industry takes a hit. This strange phenomenon, come to be referred to as Early Mortality Syndrome (EMS), picks up speed and by 2012 Vietnam, Malaysia and Thailand are reporting 90% losses. The entire industry mobilizes to discover and defend against the cause of this disastrous occurrence.
With millions of dollars in research, the culprit of EMS was found to be a strain of Vibrio parahaemolyticus, a usually harmless bacterium which in this case has evolved to create a biotoxin detrimental to shrimp hepatopancreas health. Given the name Hepatopancreatic Acute Necrosis Syndrome (AHPND), shrimp farmers and biologists across the world began the painstaking journey of understanding and thwarting the new threat to this essential agricultural industry.
A fast acting disease, the symptoms of EMS emerge within the first week of stocking a pond, and usually lead to 100% mortality before the month is out. According to, The Fish Site, symptoms include:
- Erratic swimming or swimming near the bottom of the pond
- Reduced growth
- whitening of the hepatopancreas
- reduction in size of hepatopancreas
- Soft texture of the exoskeleton
- Dark spots or streaks on the hepatopancreas
- Hardening of hepatopancreas
Fast forward 5 years, and the farmers have begun to revolutionize the way they handle biosecurity. With the introduction of highly filtered ponds, use of replaceable plastic liners and intensive airlock and washing procedures, the threat of EMS has been reduced, but not eliminated. Even experimental polyculture closed systems, such as the one created by Chaiwairuth Arunsopha and described here by Wudan Yan, are not foolproof against EMS. In fact, despite the measures taken to prevent spread of the disease, this past year the USDA confirmed reports of the first EMS case in the United States.
With no obvious cure and current preventative measures working mediocre at best, the farmed shrimp industry will have to think outside the box to solve this dynamic threat.
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