Boundaries

This ecoregion stretches across the north coast of the island of New Guinea from the Schouten Islands in the west to the Huon Peninsula in the east. It includes the drainages north of the Central Highlands, which run the length of the island.

Topography

The topography of this ecoregion ranges from lowland alluvial plains to the northern slopes of the Central Highlands. Some of the coastal mountains in the ecoregion include the Van Rees, Torricelli, Prince Alexander, Aldelbert, Finisterre, and Saruwaged mountains.

Freshwater habitats

The large river basins of this ecoregion are characterized by braided and meandering river channels and alluvial plains, with insignificant delineations between the basins. As a result fish species occur throughout the ecoregion, although the Central Highlands form an effective barrier to the south (Allen 1991).

Terrestrial habitats

This ecoregion is composed of Yapen rain forests, Northern New Guinea lowland rain and freshwater swamp forests, Northern New Guinea montane rain forests, Central Range montane rain forests, Huon Peninsula montane rain forests, and Central Range sub-alpine grasslands (WWF 2001).

Description of endemic fishes

This ecoregion contains 50 endemic species. Nearly half of the ecoregion’s endemics are in the family Melanotaeniidae, including endemic genus Glossolepis and near-endemic Chilatherina. Some other endemic genera include Pardachirus, and Brustiarius. Endemic species include Chilatherina sentaniensis, C. bulolo, and C. bleheri; Glossolepis dorityi, G. incisus, G. pseudoincisus, G. maculosus, and G. wanamensis; Melanotaenia corona, M. maylandi, and M. vanhuerni. Some lacustrine areas of endemism include Lake Holmes (Danau Bira), which contains C. bleheri and M. maylandi; Lake Sentani, which contains C. sentaniensis and G. incises; and Lake Wanum, which contains Glossolepis wanamensis (Allen 1991; Polhemus et al. 2004).

Justification for delineation

The ecoregion follows North Coast Ranges and Valleys and associated offshore islands endemic region identified by Allen (1991) and Polhemus et al. (2004). It includes many areas of endemism, such as the islands of Biak and Supiori, which boast endemic Gerridae and Notonectidae species. Yapen shares affinities with the north coast of Irian Jaya, but it also has endemic species of Zygoptera and fishes. Other areas of endemism include the Mamberamo basin and Sepik-Ramu-Markham basins as well as coastal mountain areas. The ecoregion is distinguished by two endemic genera, Chilatherina and Glossolepis.