Keeping up with the demands for fish and shellfish (especially shrimp) means corners get cut. Via Bloomberg, these details:

About 27 percent of the seafood Americans eat comes from China—and the shipments that the FDA checks are frequently contaminated, the FDA has found. The agency inspects only about 2.7 percent of imported food. Of that, FDA inspectors have rejected 1,380 loads of seafood from Vietnam since 2007 for filth and salmonella, including 81 from Ngoc Sinh, agency records show. The FDA has rejected 820 Chinese seafood shipments since 2007, including 187 that contained tilapia.