World Distribution of Rainbow Trout (Salmo gairdneri)

Since 1874, the endemic range of the rainbow trout, Salmo gairdneri Richardson, has been extended through introduction to include eastern North America and the continents of Africa, Asia, Australasia, Europe, and South America. The present range of the species extends into low latitudes by the use of waters at high elevations to over 4500 m above sea level.Environmental factors considered to be of primary importance in the survival of introduced populations are water temperature and precipitation. The presence of suitable spawning grounds, coupled with seasonal water temperatures below 13 C, are essential for the establishment of self-sustaining populations.A further extension of the world range of rainbow trout seems unlikely except perhaps in northeastern Asia. However, distribution within the present range is likely to be increased through the use of new ponds and reservoirs as they are constructed for water supply and flood control by many countries throughout the world. The farming of rainbow trout, now of local significance in parts of eastern Asia, western North America, and central and western Europe, offers an unrealized potential on all continents if warranted by a protein and market demand.