Tlxe Food of Young Fishes. 83 



In the effort to increase the valuable fishes of a lake or 

 stream, it is not sufficient that the food of these species 

 should be increased alone, but at the same time special 

 measures must be taken to secure a corresponding multi- 

 plication of the predaceous fishes themselves, otherwise 

 precisel}^ the reverse result may be produced from that in- 

 tended. 



As a further illustration of some of the practical bear- 

 ings of these facts, it may be noticed that the free access 

 of fishes to the ponds, lakes and marshes connected with a 

 stream is a matter of the highest importance. Kunning 

 water is relatively destitute of Entomostraca, and hence 

 fishes denied access while breeding to slow or stagnant 

 water in which Entomostraca abound, have no chance to 

 multiply. The condition of fish life in the lower Fox R, 

 will illustrate this point. This stream takes its rise in the 

 numerous lakes of northwestern Illinois and southern 

 Wisconsin, l)ut in its lower course has few branches and 

 no stagnant waters draining into it. Its own current is 

 swift and much of its bed is rocky, while the vast expanse 

 of water of which it forms the outlet prevents any great 

 oscillations of its level with the consequent flooding of ad- 

 jacent lands. This part of the stream is therefore pecu- 

 liarly unfit for breeding purposes, and we should expect few 

 fish to maintain themselves in it if denied access to the 

 immense and teeming breeding grounds of the upper part 

 of the river. Such access is effectually cut off by several 

 dams, unprovided with fishways, which have been thrown 

 across the stream. A fish which enters the river from 

 al)ove therefore cannot get back to breed, — a fact which 

 must unfavorably affect the number of fishes in both river 

 and lakes, and is apparently one cause of an unusual scar- 

 cify of game fishes in that stream. 



