A formal petition to the U.S. government calls for sanctions on Chinese seafood imports as it highlights China’s loophole-ridden illegal shark fin trade.By Johnny SturgeonFor migrant workers trapped onboard Chinese distant water fishing fleets, cutting the fins off sharks as they writhe violently on rusted decks in the Indian Ocean isn’t accidental. It’s an intentional and lucrative act that marks the start of a bloody half-a-billion-dollar offshore supply chain, tacitly supported by Beijing yet covertly concealed from port inspectors globally.