Shrimp farms in Asia are getting new technology and advice on how to control early mortality syndrome (EMS), but there’s still a lot of work to be done, according to Global Aquaculture Alliance (GAA) President George Chamberlain.
Chamberlain delivered an update recently to members of the National Fisheries Institute Shrimp Council, where he discussed the status of the disease worldwide and efforts to fight it.
In China, the disease has not appeared in the north, where farms have not been stocked, but eastern and southeastern operations, particularly along the Pearl River and Zhangjiang regions, have “moderate to high rates” of the disease, Chamberlain said.
Thailand, Chamberlain said, continues to take a beating. First quarter estimates from 2014 show three months of low temperatures and stock failure rates of more than 30 percent led to only 30,000 metric tons (MT) of production, versus 100,000 MT over the same period last year.
Despite the warnings, the shortage of shrimp has driven prices higher, which has led to a boom in aquaculture expansion in Vietnam, though with prices dropping more recently to USD 5 (EUR 3.68)/kg, there are fewer farms stocking.
But there are some bright spots: Malaysia production remained low overall, but a farm run by Agrobest appears to have growing volumes. Farmers in Mexico, despite outbreaks of EMS at Nayarit and here and there in Sonora, are doing well, especially with new farms in the south and on the Gulf of Mexico. Chamberlain said the GAA is predicting a yield of 55,000 to 60,000 MT in head-on shrimp.
And in India, where the disease was thought to have appeared, the science is “inconsistent and inconclusive.”
“The country’s producers should be considered free of EMS at the present time,” he said.
Chamberlain said research shows EMS may be transmitted vertically (on the outside of eggs) from broodstock to postlarvae. It is also believed to transfer to shrimp via water, cannibalism, feces, plankton, macro-organisms, birds and biofilms. Chamberlain offered a number of recommendations of what shrimp farmers should do to control the disease. They include:
- Don’t use antibiotics. Studies in China and Mexico find “the full range” of antibiotics are not effective in controlling the vibrio parahaemolyticus bacteria believed to be causing the disease.
- Make sure to use EMS-free broodstock. Selective breeding for resistance to EMS could be helpful.
- Improve farm practices. Be sure to monitor water and bottom quality, disinfect with chlorine or ozone, and possibly use probiotics and polyculture to condition the water. Avoid overfeeding stocks, too, and remove bottom sludge regularly.
- Employ a nursery phase. It allows farmers to monitor the stock more carefully, and keep juvenile shrimp isolated, possibly long enough to mature to the point where they will be immune to the disease.
- Improve farm infrastructure. Use small, deep ponds covered with plastic or bird nets to make disinfection more manageable.
- Identify feed additives that reduce the incidence of EMS. These could include quorum-sensing inhibitors, essential oils or immunostimulants.
As part of ongoing efforts to study and fight the disease, Chamberlain said the GAA is also launching a new online survey to collect data on farms reporting the presence of EMS. The World Bank Allfish project, the Seafood Industry Research Fund at the National Fisheries Institute and C.P. Prima of Indonesia are all funding the survey. The GAA expects to follow up on the survey with site audits of farms to help figure out the best practices to fight EMS.
