Fish introductions in California: History and impact on native fishes

Since 1871, at least 50 species of fish have been successfully introduced into California's inland waters, and numerous transfers of native fishes have been made between isolated drainage systems. Introductions were made of sport fish, commercial fish, forage fish, bait fish, fish for weed and insect control, and aquarium fish. Most of the introductions were authorised, reflecting a dissatisfaction with the native fishes, but in recent years unauthorised introductions have become common. The continuing decline of the native fish fauna seems to be largely the result of habitat change but introduced fishes may have contributed to this decline through competition, predation, and hybridisation. The lack of information on the native and introduced fishes of California, and their interactions, demonstrates the critical need for a statewide natural history survey.