Definition of "catadromous"
adjective
comparative more catadromous, superlative most catadromous
(ichthyology, of a migratory fish) Living in fresh water as an adult, but breeding in the sea.
Quotations
Bird migration routes favor marshes and river valleys, as do, more obviously, the movement of anadromous salmon and, the mirror image, catadromous eels, to mention only two of the numerous migrating fish species.
2017, James C Scott, chapter 1, in Against the Grain, New Haven & London: Yale, page 53