The largest fish to walk on land, the voracious northern snakehead, will flee water that is too acidic, salty or high in carbon dioxide. How does it do it? It has the most unusual ability to breathe inside and outside of water. The younger fish are good at moving short distances on land. They have sharp, dagger-like teeth, and canine teeth on their lower jaw. They are carnivorous and are native to China, southern Siberia, and North Korea, where it is fished and occasionally raised for food. It is also being introduced around the world, including most recently, the United States, where the invasive species has caused environmental problems.