Australia's freshwater habitats from Australia's other year-round rivers. As with its terrestrial flora, Southwest Australia's Mediterranean climate and biogeographic isolation has given rise to a distinct freshwater ecoregion with many endemic species. There are fifteen freshwater fish species, including nine exclusively freshwater species, three estuarine species adapted to brackish water, and three diadromous species that spend part of their life-cycle in the sea. The exclusively freshwater species are endemic to Southwest Australia, as are two estuarine species. The salamanderfish (Lepidogalaxias salamandroides) is the sole species in the endemic family Lepidogalaxiidae. Salamanderfish can aestivate during the summer months, an adaptation to the region's dry summers. Other endemic species are the nightfish (Bostockia porosa), western mud minnow (Galaxiella munda), black-stripe minnow (Galaxiella nigrostriata), Balston’s pygmy perch (Nannatherina balstoni), western pygmy perch (Nannoperca vittata), and western galaxias (Galaxias occidentalis). Southwest Australian varieties of the diadromous common galaxias (Galaxias maculatus) and spotted galaxias (Galaxias truttaceus) have adapted so they can live their life-cycle and reproduce in fresh water. The southwestern snake-necked turtle (Chelodina colliei) and western swamp turtle (Pseudemydura umbrina) are aquatic species endemic to Southwest Australia. History The first evidence of human habitation of the region was 50,000 years ago at Devil's Lair by ancestors of today's Aboriginal people. Aboriginal populations were generally denser on the coastal plain and along the coastal forest edge, and in the interior woodlands and shrublands, particularly near permanent streams and river estuaries. Population was sparse in the forested areas of the south. Offshore islands were likely uninhabited. The Aboriginal inhabitants deliberately set fires to manage the land and vegetation. Evidence from lake and estuarine sediments and firsthand accounts suggest that fire intervals in well-settled areas were frequent – from one to ten years – compared to unoccupied forests and offshore islands, where fire intervals were 30 to 100 or more years. Frequent burning reduced tree cover and encouraged the growth of grasses, herbs, and low shrubs, fostering open woodlands and savannas and limiting areas of dense forest and thicket. Noongar peoples inhabited the western and southern portions of the region. The Noongar comprised 14 groups, which spoke distinct but mutually-intelligible languages. The Nyoongar seasonal calendar includes six different seasons in a yearly cycle. These are Birak, Bunuru, Djeran, Makuru, Djilba and Kambarang. Each of the six seasons represents and explains the seasonal changes seen annually. The flowering of many different plants, the hibernation of reptiles and the