254 Roosevelt Wild Life Bulletin 



As concerns game fishes and their relation to their physical and 

 biological environment, while lakes and ponds in some ways and 

 in some localities may be considered as distinct, in other ways and 

 in other localities they are intimately bound together and cannot be 

 considered otherwise in connection with certain fishes. 



There are some fishes which pass their entire life in a lake or in 

 a stream, at no stage of their existence migrating from one to the 

 other. Again there are others which pass a part of their life in the 

 lake and another part of it in a stream. Certain primarily lake fishes 

 enter streams to breed, and cannot successfully breed elsewhere. 

 The young of some of these pass their early life, which may be 

 from a month or two to a year or two, in the stream. The young 

 of still others almost immediately after hatching either actively or 

 passively enter the lake. Still others which are hatched in a lake 

 soon after birth make their way into streams. In some streams 

 phenomena similar to those mentioned in relation to lake and stream 

 are observed in the relation of the larger stream to its tributaries. 

 So in planting fish in lakes or streams it is essential to know what 

 their habits are in this respect, for upon that knowledge successful 

 stocking to a great extent depends. 



The relation of lake and stream or large stream to smaller stream, 

 however, is not restricted to propagation and young fish. Some fish 

 enter tributary streams from a lake or large stream as adult fish 

 for other reasons than that of propagation. It may be for food, 

 or it may be for some other reason, as temperature, for instance. 

 The sojourn in these tributary streams is more or less temporary. 

 For example, there are known instances of brook trout leaving a 

 lake and appearing in considerable quantities in a tributary stream 

 where they remain for some time, then disappear, and absolutely no 

 trout of any size can be found there. Still other instances, capable 

 of definite citation, are those where large trout occur and remain in 

 the lake and never ascend a stream, unless to spawn, and sometimes 

 not even for that purpose. But small trout up to ten inches or so 

 in length ascend the brook in the spring, or summer, during stages 

 of high water in the brook and return to the lake when the water 

 of the brook subsides, or warms up. Sometimes also, while large 

 trout spawn in the lake, smaller trout ascend the streams for that 

 purpose and remain there all winter, returning to the lake in the 

 spring or summer. 



Suitability of Waters for Fish. A Utopian wish of the fish cul- 

 iurist is for a simple method by which he can determine the favorable 

 localities and conditions in which to plant fish. The oldest method 

 is similar to that of the pioneer farmer who in the virgin forest 

 chooses the land for his farm by selecting the land with the best 

 forest. He assumed that, generally speaking, the best soil produced 

 the best timber. The fish culturist has tended to assume that waters 

 already having thriving fish are favorable waters. This method still 

 remnins the most practicable for remote or inaccessible waters. In the 

 nld days this was about all that was needed or expected, but condi- 



