Even as Washington tightens screening of imports from China to block items suspected of being produced by the forced labor of ethnic minority Uyghurs, the seafood industry that supplies a large portion of the fish consumed in the U.S. has largely escaped scrutiny. A recent investigation found that China has been sending numerous Uyghurs to work in seafood-processing factories on the country’s east coast — often against their will — and using elaborate ruses to hide the use of forced labor.