The occurrence and distribution of exotic fishes in the open waters of the United States were traced by Robins et al. (1980) and Courtenay et al. (1984, 1986, 1991). In 1980, Lee et al. (1980) found that in addition to the 790 native fishes that inhabit freshwaters of Canada and the United States, 32 exotic fish species had been released and were believed to have become established in the waters of North America. The range distributions of all species were presented. Since 1978, the National Fisheries Research Center of the U.S. Fish and Wildlife Service in Gainesville, Florida, has been monitoring the status, distribution, and potential effects of all known exotic fish species in the open waters of the United States (Williams and Jennings 1991). To date, 126 species of exotic fishes have been taken from the open continental waters of the United States, and 46 of them are established. The National Fisheries Research Center, now under the National Biological Survey, developed a computer database with information on all exotic fish species taken from waters of the United States. More than 10,000 entries are in the database; 46 exotic fish species are established in the waters of the United States, and another 80 reported but unestablished species were identified (Table 7). In addition, Courtenay and Taylor (1984) identified 168 species of native fishes in the United States that were transplanted beyond their original ranges into other parts of the country, nine of them into Florida. Courtenay (1993) provided a recent review of the biological pollution from the movement of exotic species, their effects, pathways, and possible future controls. Courtenay and Stauffer (1990) pointed out that of the 46 exotic fish species, at least 28 and possibly as many as 30 are popular in the aquarium trade and hobby. Most of these tropical fish species are not well suited to the ecosystems into which they were introduced; therefore, many have only established localized populations. Many have made little, if any, known changes in the receiving ecosystem. Others that were introduced into already stressed or altered ecosystems found favorable conditions, and their populations exploded and are causing clear, immediate changes, especially in the southwestern United States. In Florida, only few of the species have had any significant impacts. Frequently, impacts from introductions are confounded by other changes in the environment and cannot be accurately determined. Sheldon and Smitherman (1984), Courtenay and Stauffer (1990), Courtenay and Williams (1992), and Davidson et al. (1992) discussed the introduction of exotic species for aquaculture, and Kushlan (1986, 1987) discussed the environmental changes exotic fishes made in the Florida everglades.
Annual sales of aquarium fishes in the United States range from 75 to 350 million fishes, averaging 20 fishes in each of 16.3 million households. This approximates about 326 million aquarium fishes valued at between $115 and $344 million in the United States. Axelrod (1971) estimated that 20 million aquaria are in homes, 6,000 in pet stores, and 1,000 in variety stores selling aquarium fishes and supplies and that more than 450 manufacturers and importers of aquarium supplies are in the United States. He stated that the three largest suppliers had annual retail sales of more than $350 million. In addition to sales of the fishes are sales of aquaria, air pumps, filters, foods, medications, and other supplies and profits from fish culture, breeding, holding, and shipping facilities (Courtenay and Stauffer 1990).
