In the heart of North America, on the border of the United States and Canada, stretches the vast Great Lakes system, which has attracted travelers for years with its monumental size and extraordinary landscapes. The depths of these bodies of water also hide less visible, but no less fascinating stories, such as the one about the sea lamprey – a seemingly harmless fish that has become a threat to local ecosystems. For years, Niagara’s natural barrier protected the Great Lakes from this predator, but as infrastructure developed, its path northward was opened. The effects on the ecosystem have been shocking.