Bass Strait Drainages




Peter Unmack



Major Habitat Type

Temperate coastal rivers

Drainages flowing into

Indian Ocean

Main rivers to other water bodies

Several coastal rivers including the Tamar, Mersey, Forth, (all in Tasmania), Tarwin, Bunyip, Yarra, Barwon, Lake Corangamite, Hopkins and Glenelg occur within this ecoregion.



This ecoregion covers the northern half of Tasmania from the Ansons River west to the Welcome River, and a portion of the coast on mainland Australia that extends from Wilson’s Promontory west to the edge of the Murray-Darling Basin.


On the mainland, elevations reach a maximum of about 600 m in the hills at the northern edge of the ecoregion. Elevations are higher, up to a maximum of about 1300 m, in the highlands of Tasmania. In both regions the elevations drop off quickly moving towards the coast.

Freshwater habitats

This ecoregion is relatively small, covering 105,000 square kilometers or 1.3% of Australia. From the Yarra River east, coastal rivers descend from higher forested catchments and tend to have perennial flow. Rivers west of the Yarra rise in lower elevation headwaters with low gradients and portions of these drainages are often intermittent during dry periods. Most of the Tasmanian rivers are short and flow north from into Bass Straight. This is one of only two Australian ecoregions that has a significant number of permanent natural lakes. These are mostly situated in the western part of the mainland portion of the ecoregion. Some are situated in volcanic craters and tend to be deep, while others are much shallower and tend to be slightly saline.

Terrestrial habitats

A diverse range of vegetation types occurs in this ecoregion, including coastal vegetation, temperate rainforest, and open eucalyptus woodlands (World Wildlife Fund 2001a, 2001b).

Description of endemic fishes

Three species are endemic to this province: Galaxias tanycephalus (saddled galaxias), Paragalaxias mesotes (Arthurs paragalaxias), and Nannoperca variegata (variegated pygmy perch). Galaxias tanycephalus is a land-locked derivative of the diadromous G. truttaceus, spotted galaxias (Waters et al. 2000).

Other noteworthy fishes

While precise research is lacking, it appears likely that Galaxiella pusilla, dwarf galaxias, may be capable of aestivation (Beck 1985). Neochanna cleaveri, the Australian mudfish, is another galaxiid fish that is also capable of aestivation (McDowall & Fulton 1996).  Both species are found also in neighboring ecoregions.

Justification for delineation

Although the mainland and northern Tasmania are currently separated by the Bass Straight, they were connected during lowered sea-levels and thus share a similar fauna. The ecoregion is distinctive relative to Eastern Coastal Australia [807] in the species that it lacks, likely due to a former drainage divide between these regions during lowered sea levels. Despite a lack of significant topographic barriers, the fauna of the Murray-Darling ecoregion contains a number of species lacking from this ecoregion as well (Unmack 2001).

Level of taxonomic exploration

Overall taxonomic exploration is good. However, many species within this province remain poorly studied and recent evidence suggests several undescribed taxa exist within more widespread forms. At least four fish species may require revisions that may increase the number of species (e.g., Galaxiella pusilla (Unmack & Adams unpub. data), Galaxias olidus (Raadik unpub. data), Retropinna semoni (Hammer et al. 2007) and Gadopsis marmoratus (Miller et al. 2004)).


  • Beck, R. G. (1985). "Field observations upon the dwarf galaxiid Galaxiella pusilla (Mack) (Pisces: Galaxiidae) in the south-east of South Australia" South Australia Naturalist 60 pp. 12-23.
  • Elvey, W., Richardson, A. M. M. and Barmuta, L. (1996). "Interactions between the introduced yabby, Cherax destructor, and the endemic crayfish Astacopsis franklinii, in Tasmanian streams" Freshwater Crayfish 11 pp. 349-363.
  • Hammer, M., Adams, M., Unmack, P. J., et al. (2007). "A rethink on Retropinna: conservation implications of new taxa and significant genetic sub-structure in Australian smelts (Pisces: Retropinnidae)" Marine and Freshwater Research 58 pp. 327-341.
  • Hamr, P. (1992). "A revision of the Tasmanian freshwater crayfish genus Astacopsis Huxley (Decapoda: Parastacidae)" Papers and Proceedings of the Royal Society of Tasmania 126 pp. 91-94.
  • Horwitz, P. and Adams, M. (2000). "The systematics, biogeography and conservation status of the species in the freshwater crayfish genus Engaewa Riek (Decapoda: Parastacidae) from south-western Australia" Invertebrate Taxonomy 14 pp. 655-80.
  • Horwitz, P. (1990). "A taxonomic revision of species in the freshwater crayfish genus Engaeus Erichson (Decapoda: Parastacidae)" Invertebrate Taxonomy 4 pp. 427-614.
  • Horwitz, P. (1994). "Distribution and conservation status of the Tasmanian giant freshwater lobster Astacopsis gouldi (Decapoda: Parastacidae)" Biological Conservation 69 (199-206)
  • Horwitz, P. (1995). "Preliminary Key to the Species of Decapoda (Crustacea, Malacostraca) Found in Australian Inland Waters" Identification Guide no. 5 Albury NSW: Murray Darling Freshwater Research Centre, Cooperative Research Centre for Freshwater Ecology.
  • Horwitz, P. (1995). "The conservation status of Australian freshwater crayfish: review and update" Freshwater Crayfish 10 pp. 70-80.
  • McDowall and Fulton (1996). "Family Galaxiidae" R. M. McDowall (Ed.) Fishes of South-eastern Australia ( pp. 52-77 ) Chatswood, Australia: Reed Books.
  • Miller, A. D., Waggy, G., Ryan, S. G., et al. (2004). "Mitochondrial 12S rRNA sequences support the existence of a third species of freshwater blackfish (Percichthyidae: Gadopsis) from south-eastern Australia" Memoirs of Museum of Victoria 61 pp. 121-127.
  • Sokol, A. (1988). "Morphological variation in relation to the taxonomy of the destructor group of the genus Cherax" Invertebrate Taxonomy 2 pp. 55-79.
  • Unmack, P. J. (2001). "Biogeography of Australian freshwater fishes" Journal of Biogeography 28 (9) pp. 1053-1089.
  • Waters, J. M., López, J. A. and Wallis, G. P. (2000). "Molecular phylogenetics and biogeography of galaxiid fishes (Osteichthyes: Galaxiidae): dispersal, vicariance, and the position of Lepidogalaxias salamandroides" Systematic Biology 49 pp. 777-795.
  • World Wildlife, F. (2001). "Southeast Australia temperate forests (AA0409)" 2005 (2005;
  • World Wildlife, F. (2001). "Tasmanian temperate forests (AA0412)" 2005 (2005;
  • Zeidler, W. and Adams, M. (1990). "Revision of the Australian crustacean genus of freshwater crayfish Gramastacus Riek (Decapoda: Parastacidae)" Invertebrate Taxonomy 3 pp. 913-924.