Although the act is illegal in most places today, our ancestors once used plant poisons to stun fish for easy collection. Numerous nuts, roots, seeds, fruits, and leaves contain compounds that have an effect on the respiratory or nervous systems of fish—especially in still water. The stupefied fish simply float to the surface, awaiting your collection. Crushed mullein seeds (Verbascum thapsus) have been used for centuries in North America as an effective fish poison. The crushed seeds release saponins, glycosides, coumarin and rotenone into the water, compounds that can stun fish and bring them to the surface. In addition to mullein, you can also use the bark and green nut husks of black walnut (Juglans nigra) in North America, and several native plants on each of the other continents. Used in a small body of water, it can bring up fish that refuse to be caught with other methods. Again, this is illegal and unsportsmanlike, but in a dire emergency—do what you must. Just catch and gut the fish quickly to minimize the meat's exposure to these toxins. Cook until well done.