Catadromous fish are species that spend most of their lives in freshwater but migrate to the ocean to spawn. A well-known example of catadromous fish is the American eel, which lives in rivers and lakes but travels to the Sargasso Sea to reproduce. This unique life cycle allows them to take advantage of different habitats throughout their lives. These fish have adapted to thrive in both freshwater and saltwater environments. Their migration patterns are crucial for their reproduction and survival. Understanding catadromous fish helps scientists learn more about aquatic ecosystems and the impact of environmental changes on these species.