Onilahy River

Onilahy is a river in Toliara Province, southern Madagascar. It flows down from the hills near Betroka to the Mozambique Channel. It empties at St. Augustin (23.5666667°S 43.75°E / -23.5666667; 43.75), and into the Bay of Saint-Augustin.

Map of Onilahy River, Madagascar

Two species of cichlids are endemic to the river basin, but Ptychochromis onilahy is probably already extinct and the remaining range of Ptychochromoides betsileanus covers less than 10 square kilometres (3.9 sq mi).