Introduced to Qld., N.S.W., Victoria, Tasmania, South Australia and Western Australia (Ref. 7300). Rainbow trout were introduced to Australian inland waters, primarily for their sporting value. They are cool water (4-19° C) species, restricted mainly to alpine and sub-alpine waters. Self maintaining populations of rainbow trout occur in higher altitude waters of New South Wales, Victoria and Tasmania. Populations are maintained by stocking in warmer rivers and reservoirs throughout New South Wales and Victoria. Cooler waters in Tasmania mean that trout are common down to sea level. Trout populations are also present in rivers and reservoirs around Adelaide in South Australia and in the south-west of Western Australia. Populations in Western Australia are largely maintained by continued stocking as there is an absence of suitable natural spawning sites. There are also isolated populations of sea run trout in Tasmanian and Victorian streams. Because of its history of introduction into Australia, rainbow trout can genetically be considered as a single stock. It is unclear whether its anadromy is a truly genetic adaptation or simply an opportunistic behavior. It seems that any stock of rainbow trout is capable of migrating, or at least adapting to sea water, if the need or opportunity arises. They require moderate to fast flowing, well oxygenated waters for breeding, but they also live in cold lakes (Ref. 6390, 44894). Rainbow trout survive better in lakes than in streams (Ref. 26519). Adults feed on aquatic and terrestrial insects, mollusks, crustaceans, fish eggs, minnows, and other small fishes (including other trout); young feed predominantly on zooplankton (Ref. 26523).