Lakes Kutubu and Sentani are unusual small tropical lakes because they contain many species of fish that can't be found anywhere else in the world.
Usually the only time that rainbows are visible is after a hard rain. But in Lakes Kutubu and Sentani, they flash their bright colors all the time. Well, at least rainbow fish do! Species called rainbowfish, along with many others, are unique to these lakes, which are located in New Guinea, the world's second largest island.
Lake Kutubu lies in the heart of the Kikori Basin, a vast area of wetlands, grasslands, and rain forest. Its water is clear, still, and about 230 feet (70 meters) deep. Although streams flow into Kutubu and a large river takes water out, the lake is fed mostly by underground channels. Lake Sentani is much larger but only about 160 feet (50 meters) deep. It is fed by rain falling directly into the lake and by mountain streams. Water flows from Sentani to the Pacific Ocean by way of two rivers.
Lake Kutubu may be small, but it harbors 11 species of fish that live nowhere else in the world, including the Kutubu tandan (a kind of catfish), Kutubu hardyhead, Adamson's grunter, and the small, colorful Kutubu rainbowfish. Lake Kutubu also hosts several endemic fish called mogurndas. These include the Kutubu, blotched, variegated, black, and striped mogurndas. Besides having its own species of rainbowfish, Lake Sentani is also home to another fish species that cannot be found anywhere else, the Sentani gudgeon.
Cause for Concern
This ecoregion is located within one of the least populated areas of Papua New Guinea, but Lake Kutubu is threatened by overfishing and nearby oil development, with associated road-building and potential for oil spills. Introduced species could be harmful to the endemic species in these lakes.