Environmental requirements and tolerances of Rainbow trout (Oncorhynchus mykiss) and Brown trout (Salmo trutta) with special reference to Western Australia: A review

Both Oncorhynchus mykiss (rainbow trout) and Salmo trutta (brown trout) have a long history of translocation and culture and a wide knowledge base exists. O.mykiss is being considered as a candidate for inland aquaculture in the salinity affected areas of southern Western Australia and this review aims, in part, at providing relevant information to those considering a trout-framing venture in Western Australia. Both species of trout can survive a wide range of environmental conditions, including temperature, salinity, pH, dissolved oxygen and ammonia, with O.mykiss having a higher temperature tolerance than S.trutta. However, within the ranges of environmental conditions, each species has a preferred range within which survival and growth are optimal. Furthermore, survival within these ranges will be affected by synergistic interactions among variables (for example temperature and dissolved oxygen) and the presence of certain features within a habitat (for example cover and refugia). Although not conclusive, many studies suggest that selective breeding programs may be able to produce fish with increased tolerances and better survival under more extreme conditions. In the south-west of Western Australia, a selective breeding program may produce more heat-tolerant fish, presenting opportunities for trout production under a wide range of temperature conditions. Rainbow and brown trout also form the basis of a significant recreational fishery in southern, inland Western Australia and additional environmental influences on stocks within this fishery are also considered.