Knowledge of the Australian freshwater fish fauna is very good. An Action Plan for Australian Freshwater Fishes was published in 1993 (Wager and Jackson, 1993). This included status assessments for all species along with detailed recovery outlines for threatened taxa.
Australia encompasses a wide variety of freshwater habitats and boasts a relative diverse fauna. Only four Australian species have evolved as primary freshwater species. The remainder have evolved from marine ancestors. Many of the inland Australian waters have very high salinities and may be several times more saline than sea water. Australia can be divided into nine more or less distinct divisions (ref 5259).
1. Southwestern Division. Contains mainly coastal rivers that are relatively short, flowing into the Indian and Southern Oceans between about Geraldton on the western coast and about Esperance on the southern coast. Most streams are generally narrow and relatively fast-flowing. Water temperatures are cool and support introduced trout populations. Most of the larger streams in the area have extensive estuaries at their mouths. The fish fauna is dominated by galaxiids.
2. Pilbara Division. Rivers draining the central-western coast region of Western Australia and flowing into the Indian Ocean. Rainfall is generally sparse and some rivers are dry for several years in succession. Streams are generally slow-flowing ranging from clear conditions inland to turbid conditions near the coast. Grunters and gudgeons comprise around half of the fauna.
3. Kimberley-Arnhem Land Division. Includes the relatively hilly terrain in the far north of Western Australia and the adjacent part of Northern Territory. Streams are characteristically shaded. This is one of the wettest regions of Australia. The fauna is dominated by grunters and gudgeons.
4. Gulf of Carpentaria Division. This region overlaps with the Arnhem Land division to the west and the Eastern Coastal division. Some of the rivers extend for hundreds of kilometres inland. Rivers are generally sluggish and turbid. Many of the species are shared with southern New Guinea.
5. Eastern Coastal Division. This is an extensive narrow coastal region extending from the tip of the Cape York Peninsula southward to Cape Howe and west to the South Australia border. It can be subdivided into northeastern and southeastern portions, the dividing line being the New South Wales-Queensland border. In the north there are peat-stained creeks and ponds in the coastal dune systems and tropical rainforests. The southeastern segment is extensively settled by man with pockets of rainforest, coastal heathlands and dune lakes and estuaries. Gudgeons are one of the largest groups throughout the region and galaxiids are particularly common in the south.
6. Tasmanian Division. The terrain is largely mountainous and precipitation is substantial. Much of the island is heavily forested and there are numerous man-made and natural lakes. The most remarkable element of the fauna are the galaxiids, many of which are endemic to Tasmania.
7. South Australian Gulf Division. The small area consists of streams in the vicinity of Adelaide draining into the Gulf of St. Vincent and the nearby Spencer Gulf. The streams are generally short and often stop flowing during the dry summer months.
8. Murray-Darling Division. The combined Murray-Darling River System is the largest in Australia, rising in the interior of southern Queensland and flowing southeastward for 1900 km to the Southern Ocean. The headwaters of the Murray consist of forested mountain terrain and high plains, whereas much of the Darling originates in gentler terrain with dry forest and low scrub bordering on desert conditions. This division is also greatly affected by man's activities, particularly land clearing and construction of dams for agricultural purposes. The fauna is dominated by galaxiids, percichthyids and gudgeons.
9. Lake Eyre and Adjacent Internal Divisions. This region encompasses much of the central interior and is characterised by featureless desert plains, low-lying hills and gorges around Alice Springs. Temperature and salinity regimes are subject to broad fluctuations and fishes in this area are hardy and well-adapted. Common species in the fauna include plotosid catfishes, hardyheads and grunters.
Around 25% of Australian freshwater fishes are considered to have either significantly declined in distribution or are found in restricted areas. Although no fish species are known to have become extinct since European settlement, one species has become extinct in the wild. Habitat degradation and/or interactions with introduced species appear to be the main causes of declining fish populations. Many processes threaten habitat and are often interlinked They include changes to natural flow regimes, clearing of catchment vegetation, increased sediment loads, alteration of river bed and banks, reduced water quality and artificial barriers to ations. Many processes threaten habitat and are often interlinked They include changes to natural flow regimes, clearing of catchment vegetation, increased sediment loads, alteration of river bed and banks, reduced water quality and artificial barriers to ations. Many processes threaten habitat and are often interlinked They include changes to natural flow regimes, clearing of catchment vegetation, increased sediment loads, alteration of river bed and banks, reduced water quality and artificial barriers to ations. Many processes threaten habitat and are often interlinked They include changes to natural flow regimes, clearing of catchment vegetation, increased sediment loads, alteration of river bed and banks, reduced water quality and artificial barriers to fish movement. Brown trout (Salmo trutta) and Gambusia (Gambusia holbrooki) appear to be the introduced species of most threat to native species at present. The majority of the species listed as threatened in the Action Plan are found in the south-east. While this may reflect the areas of most severe habitat degradation it may also reflect the lack of adequate survey work elsewhere.
The major factor limiting development of adequate recovery outlines for freshwater fishes remains the lack of biological data, particularly relating to habitat requirements. It is recommended that the Australian Action Plan be reviewed every five years.
Contacts: Rob Wager and Peter Jackson, Queensland Depart of Primary Industries, Fisheries Division, GPO Box 46, Brisbane, Queensland 4001, AUSTRALIA.
|Geography and Climate
Australia is located in Oceania, continent between the Indian Ocean and the South Pacific Ocean. The area comparative is slightly smaller than the US. The climate in the country is generally arid to semiarid; temperate in south and east; tropical in north. Terrain consists mostly of low plateau with deserts; fertile plain in southeast. Elevation extreme has lowest point in Lake Eyre -15 m and highest point in Mount Kosciusko 2,229 m. Natural resources are bauxite, coal, iron ore, copper, tin, silver, uranium, nickel, tungsten, mineral sands, lead, zinc, diamonds, natural gas, petroleum. Land use: arable land: 6%, permanent crops: 0%, permanent pastures: 54%, forests and woodland: 19%, other: 21% (1993 est.). Irrigated land is 21,070 sq km (1993 est.). Natural hazards are cyclones along the coast; severe droughts.
Environment—current issues: soil erosion from overgrazing, industrial development, urbanization, and poor farming practices; soil salinity rising due to the use of poor quality water; desertification; clearing for agricultural purposes threatens the natural habitat of many unique animal and plant species; the Great Barrier Reef off the northeast coast, the largest coral reef in the world, is threatened by increased shipping and its popularity as a tourist site; limited natural fresh water resources.
Geography—note: world's smallest continent but sixth-largest country; population concentrated along the eastern and southeastern coasts; regular, tropical, invigorating, sea breeze known as "the Doctor" occurs along the west coast in the summer.
Ref. Anonymous, 1999