Nile perch is a fish that was introduced into Lake Victoria. The reason that fish was introduced into Lake Victoria was because it was decided that the people living near the lake needed more proteins than they were getting.
There's a measure of prescriptivism and descriptivism in every dictionary. Prescriptivism believes that the language should mirror the best practices of English, and editors are prescriptivist in so far as they don't want to let things they consider to be inelegant or ungrammatical into print.