The genetic impact of introduced fishes on native species

Abstract

The introduction of nonnative fishes or "exotics" and transplants of fishes outside their geographic range but within the same country is a contentious issue. The effects of these introductions on native fish faunas are well documented and have resulted in legislation controlling future introductions of alien species and management policies based largely on living with past mistakes. However, fish introductions also occur at two more subtle levels: transfers within the range of the species, and introduction of foreign DNA to produce "transgenics." The rationale for transfers is largely typological in that "a fish is a fish," at least as far as any given species might be concerned. Transfers disregard the concept that species are divided into genetically distinct units or "stocks" adapted to their particular environment and that introduction of nonlocal conspecifics can disrupt the genetics and adaptation of local populations. This paper raises some of the major issues and the need to synthesize the concepts, documented cases, and effects.