engendered caution. Approximately AO species of nonindigenous 

 finfish have become established in the U.S. The long term 

 ecological implication of most of these species is not known. An 

 example of a beneficial introduction is the striped bass which was 

 introduced to the Pacific coast in the late 1800' s and has since 

 produced a valuable fishery. Aquaculture, like agriculture, stands 

 to be improved by culturing productive nonindigenous species and by 

 breeding with improved strains. 



Oysters have been widely transplanted with both beneficial and 

 detrimental effects on cultured and wild oysters. The most widely 

 introduced oyster is the Pacific oyster, Crassostrea gigas . This 

 species now furnishes much of the world's oyster supply, but may 

 have adversely affected or replaced indigenous species. 



There are numerous instances in which the nonindigenous organism 

 has been a host to invertebrates that have become severe pests on 

 wild indigenous and locally cultured species. Examples include the 

 Japanese oyster drill, Ocenebra japonica , the flatworm, 

 Pseudostylochus ostreophagus and possibly the copepod parasite, 

 Mytilicola orientalis . All were introduced to North America with 

 the Pacific oyster. 



Parasites and Diseases 



Imported organisms are often accompanied by diseases and parasites, 

 sometimes with catastrophic impacts on cultured organisms and 

 occasionally on wild populations. Scientists estimate that 48 

 species of freshwater fish parasites have become established on 

 other continents through the transfer of infected live and frozen 

 fish. Almost all of the spread of freshwater fish parasites have 

 been as a result of man's activities. At least five of these 

 parasites have caused severe problems. The best example is 

 whirling disease of trout, caused by the organism. My xo soma 

 cerebralis . This parasite has caused large economic losses in 

 rainbow trout culture on three continents. 



Careful screening, certification, and quarantine could prevent the 

 establishment of most parasites and diseases. 



Genetics 



The release of large numbers of cultured species to coastal waters, 

 "sea ranching," has raised questions about the potential impact on 

 the genetic integrity of wild stocks. Interbreeding between 

 domestic and wild stocks could result in genetic degradation of 

 wild stocks. Each wild stock has a harmonious gene combination 

 suited to its particular environment. 



Changes in the genetic makeup may affect the stock's ability to 

 survive. Potential problems of mixing domestic and wild stocks 

 could be prevented through proper research and management. 



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