Couldn't the Japanese just net up the bluegill and sell them to the Chinese? Then they could make something out of it, add lead to it and sell it in the U.S.
Really though, anytime an animal/plant is introduced out of it's native habitat, you run the risk of disaster. One example is the white perch. Eagerly sought after on the East coast, but in the midwest and great lakes, they're considered an exotic invasive pest. Flathead catfish get the same designation in North Carolina.
Do gooder since April 26, 2009!