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Ecoregion Description


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Species Richness


# of Endemic Species


Threats

803: Kimberley

Major Habitat Type:

tropical and subtropical coastal rivers

Author:

Peter Unmack

Reviewers:

Helen Larson, Curator of Fishes, Museum and Art Gallery of the Northern Territory, Australia

Countries:

Australia

Boundaries:

The southern boundary of the ecoregion is the Great Sandy Desert.  The ecoregion begins in the west with the Fitzroy Basin (Western Australia) and extends east up to and including the King George Basin.

Drainages flowing into:

Indian Ocean.

Main rivers or other water bodies:

Major rivers in the region are the Fitzroy, Isdell, Prince Regent, Mitchell, King Edward and Drysdale.  These and other rivers drain from the Kimberley Plateau to the coast, which is lined with numerous bays and inlets.

Topography:

The ecoregion is dominated by rugged sandstone and limestone ranges and the Kimberley Plateau.  Maximum elevations are up to 937 m (Mt.Ord) with most of the ecoregion being between 200-600 m.  Due to the rugged topography, Kimberley Ecoregion contains more gorges than any other part of Australia.  These gorges likely provide important long-term refuges for fishes during dry periods (Unmack 2001). 

Climate:

A short, hot wet season lasts from October to March, bringing most of the region’s rainfall, often in storms associated with destructive cyclones.  Temperatures are high throughout the year and monthly average maxima range from 25oC to 35oC (World Wildlife Fund 2001). 

Freshwater habitats:

This ecoregion is relatively small, covering 195,000 square kilometers or 2.5% of Australia.  Large rivers with strongly seasonal flow patterns dissect the complex topography of this region.  Many canyons or gorges are present due to the rugged topography.  These provide important long-term refuges for the fauna during dry periods.  No major dams exist within this ecoregion.

Terrestrial Habitats:

Wooded grasslands and shrublands are the dominant vegetation types.

Fish Fauna:

A total of 48 species from 18 families are present. Many of the non-endemic fishes that occur in this ecoregion are widespread and have ranges that extend at least to the east coast drainages of Australia (Unmack 2001). The fish fauna is strongly dominated in terms of richness by the families Terapontidae (grunters) and Eleotridae (gudgeons or sleepers) with nine species each, Plotosidae (eel-tailed catfishes) has five species and Melanotaeniidae (rainbowfishes) has four species.  Two families are represented by three species, three families are represented by two species, and the remaining nine families have only one species.

Description of endemic fishes:

Fifteen species including two genera are endemic: Kimberleyeleotris (Eleotridae) and Hannia (Terapontidae). Five of nine species in the family Eleotridae are endemic (Hypseleotris ejuncida, slender gudgeon H. regalis, Prince Regent gudgeon, H. kimberleyensis, Barnett River gudgeon, Kimberleyeleotris hutchinsi, Mitchell gudgeon, K. notata, Drysdale gudgeon); four of nine Terapontidae (Hephaestus epirrhinos, long-nose sooty grunter, Leiopotherapon macrolepis, large-scale grunter, S. trigonicus, long-nose Grunter, Hannia greenwayi, Greenway\'s grunter); two of three Atherinidae (Craterocephalus helenae, Drysdale hardyhead, C. lentiginosus, Prince Regent hardyhead); two of five Melanotaeniidae (Melanotaenia gracilis, slender rainbowfish, M. pygmaea, pygmy rainbowfish); and one of two Toxotidae (Toxotes kimberleyensis, Kimberley archerfish). Several endemics have ranges limited to only one or two individual rivers. Overall 15 out of 48 species are endemic (31%).

Other noteworthy aquatic biotic elements:

Chelodina kuchlingi, Kuchling’s long-neck turtle, is known from the King Edward River (Cann 1998). The atyid shrimp Caridina spelunca was described from a single cave (Choy 1996) but is also found in surrounding surface creeks and rivers (T. Page pers. comm.).

Evolutionary phenomena:

At least some of the endemic fishes within this region are probably relictual from wetter times given that many of them have quite restricted distributions.

Justification for delineation:

The complex topography of the Kimberley and its gorges have provided some refuge from historic climate change, thus contributing to the development of a distinctive and endemic biota.  The ecoregion has a mix of relatively widespread species across northern Australia in addition to a large number of endemic species (Unmack 2001).  This suggests that some species have had little trouble dispersing into this ecoregion, but others, based on their limited distributions are unable to disperse under current conditions.  A total of 15 species are endemic from a total of 48 (31%).

Level of taxonomic exploration:

Good/Fair. While many aspects of the distribution and ecology of Kimberley fishes are poorly known, a number of species are relatively well characterized taxonomically, but many areas remain poorly sampled. Morgan et al. (2002) considered that there may be an undescribed Ambassis species from this ecoregion and it appears likely that populations of Neosilurus hyrtlii, Hyrtl’s catfish, may be separated into different species (P. Unmack unpub. data). It is possible that local populations of other widespread species may represent undescribed taxa.

References/sources:

Cann, J. (1998). "Australian freshwater turtles" Singapore: Beaumont Publishing.

Choy, S. C. (1996). "Caridina spelunca, a new species of freshwater shrimp (Crustacea: Decapoda: Atyidae) from a Western Australian cave" Records of the Western Australian Museum 18 103–107.

Morgan, D., Allen, M., et al. (2002) "Inland fish fauna of the Fitzroy River Western Australia (including the Bunuba, Gooniyandi, Ngarinyin, Nyikina and Walmajarri names)". Project Number 003123. Natural Heritage Trust.

Unmack, P. J. (2001). "Biogeography of Australian freshwater fishes" Journal of Biogeography 28(9) 1053-1089.

World Wildlife, Fund (2001). "Terrestrial Ecoregions of the World" 2005 (2005; www.worldwildlife.org/science/ecoregions/biomes.cfm).

The Nature Conservancy World Wildlife Fund
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