I may have solved the puzzle of the poisoned fish. The Ainu of northern Japan hunted deer and bear with poisoned arrows. There were various recipes for this poison but a main ingredient was the the aconitum plant - more familiarly known to us as monkshood. Tubers from the plant were gathered in the summer and dried in the shade until the fall, which was supposed to make a more potent poison. "Because the alkaloid aconitum agent was only deadly upon entering the bloodstream, it was safe to eat the meat of animals so killed as long as one removed the meat around the point of penetration." There are several species of aconitum which are native to the eastern regions where the Cherokee lived.


Source: William W. Fitzhugh and Chisato O. Dubreuil, ed. Ainu: Spirit of a Northern People. Smithsonian Institute, 1999.