The black flounder (Rhombosolea retiaria), also known by the MÃÂori language name mohoao, is a species of flatfish in the family Rhombosoleidae, found around New Zealand in shallow enclosed waters and coastal freshwater lakes. Its adult length ranges from .
Rhombosolea retiaria is known for its black back and orange spots.
Rhombosolea retiaria is the only species of flounder in New Zealand that can thrive in freshwater. It can be found in streams as far as inland from the ocean.