The price of vannamei shrimp in Vietnam has dropped about 15 percent since September. Holiday demand in the United States has run its course, and though China had to import to meet demand earlier in the year, a sluggish economy there has reduced demand allowing it to meet its needs with domestic production.

Early Mortality Syndrome (EMS) in Thailand from last year halved that country‚Äôs output, boosting prices by 40 percent. The high prices stimulated farmers in Vietnam and Indonesia to switch…