270 Roosevelt Wild Life Bulletin 



iish. Sometimes this supplantation has teen because the conditions 

 were best suited to the introduced fish and the native fish would 

 never have amounted to much in that particular water. Sometimes 

 the ascendency of the introduced fish is attributable to the direct 

 effect of the voracit}- of that form, and the decrease or disappearance 

 of the native fish is chargeable to the same factor, that is, the first has 

 eaten the other. IMore often the effect of the voracit}^ of the 

 introduced form is an indirect one, that is, it becomes a competitor 

 for the food supph- in which its voracit}- and actiA-it\- gives it an 

 advantage. Occasionally the supplanting has been with a fish superior 

 to the native fish, but more often one which in its new environment 

 becomes inferior in one or more ways. There are instances of waters, 

 originally containing no game fish whatever, which by the same 

 haphazard " experimentation " have proved eminently suited to one 

 or another fish. ]SIore often the experiments have sooner or later 

 resulted in failure. Some of the failures may be attributed to un- 

 suitable waters, to improper planting methods, or perhaps to too 

 small numbers planted to offset inevitable natural loss. 



It has occasionally happened that acclimatization has been effected, 

 not in the immediate waters where the fish were planted, but in 

 some other portion of the water sj'stem. In such cases it is unneces- 

 sary- to say, the fact is attributable to more suitable waters in the one 

 than in the other place. Such successes as these are due largety to 

 chance selection of suitable water and often repeated introductions. 



It is natural to beheve that waters which have been depleted of 

 the indigenous species could best be stocked by the same species 

 that originally inhabited them. If the fresh waters of the entire 

 State had to be restocked with fish, the logical species would appear 

 to be those of general distribution in the State, but it does not 

 necessarily follow that the original inhabitants of a given body of 

 water are best suited to it. or rather that others will not thrive there 

 as well as the original inhabitants, or even better. 



Usually there are more or less restricted localities which are 

 ideally adapted to fish that do not occur there, and are less or even 

 ill-suited to the fish of general distribution in that body of water. 

 For instance, because fish which are common in the lower course 

 of a stream occur to some extent in its upper course, it does not 

 signify that some other kind would not thrive or even do better 

 than the originals in the latter locality-. Or the reverse may be the 

 case. 



Bv various means the original conditions of some waters may 

 have been so modified that they are no longer suitable for the species 

 originally occurring there, but still may be suitable for some other 

 species. Mr. Whitaker was right on general principles, but circum- 

 stances alter cases. Where a body of water, lake or stream is 

 depleted but stiU inhabited by indigenous fish which are all that 

 could be desired or expected in food and game qualities, the cause 

 of depletion should be ascertained, and if changed conditions are 

 not the cause of depletion the natural stock should be restored. In 

 the other instances mentioned the logical thing to do is to ascertain 

 to what kinds of fish the wuters are best suited and act accordingly. 



