If you are a fish, and you live in fresh water, but you swim to the ocean to breed, then you are catadromous. This is the reverse of the best known salt- and freshwater fish, the salmon, who swims into fresh water to breed.
European eels are catadromous.
So a catadromous fish runs in reverse. Anadromous fishes swim from the ocean into rivers or streams to breed. Inc. All rights reserved. Cool Word of the Day is a trademark of The Learning Kingdom, Inc.