The US imports about $4-5 billion worth of shrimp every year, a mix of fresh, frozen, and prepared products. Most of it comes from southeast Asia, but some is from Latin America, and in particular Ecuador and Mexico (not shown).
(source data from the USDA's Economic Research Service)
As you can see, for a long time Thailand has been the biggest exporter of shrimp: they are blessed with a lot of mangrove coastline, and farming shrimp is extremely profitable, so naturally there are a lot of people in the business. Unfortunately, the business apparently isn't very well regulated: wastewater from one farm is often the intake water for the next farm downstream, so diseases like "
early mortality syndrome" can sometimes run amuck, devastating the entire country's production. That's the cause of the drop in the graph above. Making matters worse, the NYT recently had a piece about
slavery on board shrimp boats. (Shrimp are both farmed and wild caught in places.) With all the chaos in the Thai government these days, I doubt that regulations will soon clean up the industry.
Notice that others such as India are stepping into the gap. In 2008 and 2009, India produced just about $150 million worth of shrimp, but in 2013 they broke the $1 billion barrier, increasing exports to the US by a factor of six over just five years. It's definitely possible to have a cleaner production system: according to the Monterey Bay Aquarium's "Seafood Watch" guide, the
best choices for shrimp are from aquaculture done in North America. It is much less damaging of the environment, and I'd think that it's less likely to involve slavery as well. If Thailand reins in the human rights abuses, their costs will probably go up, giving India and others even more of an opening. A market that works is a good thing for everyone!
