92 U. S. BUREAU OF FISHERIES. 
the recommendation of a friend or because the species has afforded 
him pleasure in another region. The importance of making a careful 
survey of the waters to be stocked, with the view of determining the 
species best adapted thereto, is often not recognized. It has been 
proved beyond a doubt that in nearly every case it is advisable to 
plant a species which is native to the locality, and in specifying his 
choice of fish the applicant should bear this in mind. Nonindigenous 
species should not be introduced unless it can be clearly shown that 
the native species, because of changed conditions, have failed to 
maintain themselves. There are many notable examples of the suc- 
cessful transplanting of fishes where the results have been highly 
beneficial. However, there is always an element of uncertainty in 
the planting of nonindigenous fishes in any region, and it should be 
undertaken only after a careful consideration of all phases of the 
situation, because 1f promiscuous plantings were to be permitted the 
work of fish culture might easily become a curse instead of a blessing 
to mankind. 
The carp is an appropriate example of the results of the indis- 
criminate introduction of a foreign species. This fish was popular 
in the early history of fish culture in America, largely, perhaps, 
_because it was a favorite with European fish-culturists and because 
of its rapid growth and ready adaptability to new surroundings. 
Through carelessness and indifference the carp became widely dis- 
tributed in the waters of the country, with the result that in many 
sections a stigma will always apply to this sturdy fish. Neverthe- 
less, there is a place in the piscatorial world for the carp, and for 
certain waters it fills a demand that can not be adequately met by 
any other species. It frequently happens that carp can be success- 
fully and profitably propagated in waters that are quite unsuited to 
the finer species; and, under proper restrictions, this idea should be 
encouraged. 
Aside from possible injury to indigenous species that may follow 
the introduction of foreign fishes, there are other important points 
to consider: Will the new inhabitants find a suitable temperature 
range and other conditions congenial to their reproduction? Will 
the food supply be of a suitable character and ample for their needs? 
Unless these essentials are present an introduced species can not 
establish itself in a new environment on a self-maintaining basis. 
Not infrequently species of fishes that are possessed of the highest 
food and game qualities in their natural habitat will, when trans- 
planted in less favorable surroundings, degenerate to a point where 
they have no attractions either from a food or a game standpoint. 
Even the planting together of the same species of fish taken from 
different sections of the country or from different streams in the 
same section may be inadvisable. Certain investigators have ex- 
pressed the belief that such plantings may lead, or in certain instances 
may have already led, to a form of hybridization which may result 
in seriously impairing the virility of the progeny. 
Many of the more progressive State fish and game commissions 
have requested that all applications for certain species of nonindige- 
nous or predacious fishes be submitted to them for approval. The 
bureau commends this policy, and all such applications, including 
those for carp, are referred before acceptance for the proper State 
