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THE INTRODUCED SPECIES PROBLEM Ecosystems Disrupted Many aquatic and terrestrial species have been introduced into North America. A study by the Office of Technology Assessment (USOTA 1993) concluded that introductions of harmful species have produced cumulative impacts and: "...are creating a growing economic and environmental burden for the country." The report states that 4,500 foreign species have established populations in the United States. Many of these introductions were intentional, but others occurred unintentionally through human activities (Taylor et al. 1984). Humans have a penchant for supplementing their local biological environment with imported plants or animals that are perceived to have special beauty or usefulness, or are simply reminders of a pleasing biological environment in another geographic location. Exotic species have been introduced from Europe and other continents with the intent of benefitting their "new ecosystem" in the United States. But most exotic species were the bane of, rather than a benefit to, new environments, and there are many examples of harmful introductions. One of the first species to be introduced into the United States was common carp. The carp was stocked across the country as a recreational and food fish by federal and state agencies, but the folly of this action soon became apparent as it caused great losses to fish habitat and displaced native fish populations (Fuller et al. 1999). For several decades, common carp has been considered one of the most undesirable species in North America, and targeted for population reduction or eradication (Wydoski and Wiley 1999). However, introductions of other fishes have continued, and predaceous and highly competitive species such as the ruffe (Gymnocephalus cemua; native to Europe and Northern Asia), which was introduced into the Great Lakes, and various species of snakeheads (Channidae; native to Africa and Asia), which now occur in several states (e.g., Oberg 2002) are recent examples of highly undesirable introductions. Finally, recent alarm over the imminent invasion of the great lakes by exotic silver, bighead, and black carp (Hypophthalmichthyes, Mylopharygodon) is due to predictions that these fishes would have even greater adverse impact on the Great Lakes ecosystem than the zebra mussel (Great Lakes Fishery Commission 2002), which imposed enormous economic hardships on water and power industries (Nalepa and Schlosser 1993). Although most of the preceding examples of exotic introductions were due to accidental or unintentional releases, it is important to point out that many fishes have been intentionally introduced into waters of the United States where they are not native species. The overwhelming numbers of these introductions have been due to actions by responsible government agencies, ostensibly for "beneficial purposes ". These introductions have included such diverse purposes as providing food resources (e.g., the 13