What does the term catadromous mean?

The term catadromous refers specifically to fish that migrate down rivers to the sea to spawn. This lifecycle pattern is seen in species such as eels. In a catadromous system, adult fish spend the majority of their lives in freshwater environments, but when it comes time to reproduce, they make an upstream journey to the ocean, where they spawn. This contrasts with fish that are known as anadromous, which migrate from saltwater to freshwater to spawn. The life cycle of catadromous fish showcases the importance of both freshwater and saltwater environments in their reproductive strategies.

The other options illustrate different migratory patterns or habitats but do not correctly define catadromous behavior, which is specifically tied to the transition from freshwater to saltwater for spawning purposes.