What does anadromous mean?

The word anadromous means migrating up fresh water rivers from the sea, to breed. Salmon are anadromous. Anadromous fish born in fish water spends most of its life in the sea returns to freshwater to spawn. Smolt, shad, striped bass and sturgeon are common examples. Castration's fish dose the opposite - lives in fresh water and enters salt water to spawn.  Most of the eels are catanadromous.