Why were rainbow trout and brown trout introduced to waters outside their native ranges?

Rainbow trout and brown trout have been widely introduced to waters outside their native ranges primarily to serve as sport fish. Because these species are highly valued by anglers for their fighting ability and size, government agencies have historically stocked them in regions where such large predator fish were previously absent or where the demand for recreational fishing exceeded the natural supply.123

The introduction of these species has been particularly successful in areas like Africa, South America, Australia, and New Zealand. In these environments, the trout often flourish by feeding on local species, such as those in the families Retropinnidae and Galaxiidae, allowing them to grow to trophy sizes. Additionally, the brown trout is frequently transplanted because it is capable of thriving in warmer water conditions than many other trout species.24