Stocking and introduction of fishes began in Newfoundland and Labrador in the early 1880s. Introduced non-native fishes and stocking of native fishes beyond their local range have established populations in many areas. Competition, predation and the possible introduction of parasites and diseases have all resulted from such stocking and introductions. Direct genetic effects have been caused by interbreeding with native species. Indirect genetic effects may have resulted from selective forces, genetic drift and inbreeding. Aquaculture and the creation of transgenic fish also pose a new threat to native fish. The effects of introductions as mitigation or enhancement tools are discussed. Although Newfoundland and Labrador is still relatively pristine, safeguards must be introduced to reduce the potential detrimental effects of these management practices.