Propagated Fish in Resource Management

Unauthorized Fish Introductions: Fisheries Management of the People, for the People, or by the People?

Frank J. Rahel


Abstract.—Although agency-authorized stocking of sport and forage fishes was the most common reason for fish introductions in the past, unauthorized introductions are now a major reason for the spread of nonnative fishes. Of 62 unauthorized fish introductions documented in Wyoming during 1973–2002, half (50%) involved the deliberate and illegal release of species by the public. These illegal introductions involved 23 taxa and included sport fish, baitfish, and aquaria fish. Colonization events involving the unwanted movement of fishes into new water bodies constituted 34% of unauthorized introductions and involved 13 species. Inadvertent introductions whereby species were introduced unknowingly, often as contaminants in authorized fish stockings, constituted 8% of unauthorized introductions. The remaining 8% of unauthorized introductions involved cases where the source of the nonnative fish was unknown. Options for reducing the number of unauthorized introductions include educating the public about the negative consequences of unplanned fish introductions and enacting legislation that restricts the public’s access to species deemed undesirable if released into local water bodies. Because control or eradication of nonnative fishes is expensive, logistically difficult, and sometimes controversial, it will be feasible in only a limited number of situations. In most cases, we will have to accept unauthorized introductions as potentially leading to permanent additions to the regional fish fauna.