Black Tiger Shrimp AKA Monodon (right)
These two species makeup over 80% of the shrimp farmed in marine and brackish waters. If you have eaten shrimp lately, it is likely from one of these two species.
The big risk with having monocultures like these is the constant threat of disease. It slammed Thailand and India in the 1990's and has been a persistent problem ever since. Luckily farms have implemented much stricter biological controls to avoid disease at all costs.
There are other species of marine shrimp that are farmed, but they are often done so for the local market and are less of commodity than vannamei or monodon.
These are primarily grown in China and represent a much smaller portion of the shrimp that gets exported around the world.