Anadromous:
going from salt water to fresh water or up rivers to spawn: said of salmon, shad, etc. [Your Dictionary]
Noted in “These Prehistoric Ocean Animals are Still Around Today,” Ocean Currents:
Since lampreys are anadromous fish (fish that live in fresh and saltwater), they play a major role in healthy estuaries—transporting nutrients from the ocean to freshwater environments. Due to increased human disturbances, lampreys are severely declining, which has the potential to affect entire ecosystems.
The usage might be a bit inaccurate. Does the definition, as understood by marine biologists, include the requirement that the fish die after the spawning?
[h/t JN]
