40 NORTHERN FISHES 



are best developed in the feeder streams. Frequently streams have so 

 much vegetation that they are partly choked by it. This situation 

 should be remedied by removal of part of the cover. 



Streams in which the water reaches a temperature of over 70° F. for 

 a considerable period during midsummer cannot be considered good 

 trout streams. If they are of fishable size they may be capable of sup- 

 porting smallmouth and largemouth bass, sunfishes, and even walleyes 

 and northern pike, and many can be improved to furnish better fish- 

 ing. As such streams are usually rather large, the cost of mechanical 

 devices for pool shelters and feeding beds may render improvement 

 impracticable. Pollution is a serious factor in rendering many of these 

 streams sterile and can be remedied only by complete elimination. Silt 

 from farmers' fields is just as serious a problem in these warm streams 

 as in the trout streams and can be remedied only by reducing soil 

 erosion. 



The seining of minnows for commercial purposes has greatly increased 

 in recent years. Such seining should be stopped, for it not only destroys 

 a valuable food source but also disturbs and damages the spawning and 

 feeding beds. Small M^arm streams, though not of sufficient size to sup- 

 port adult game fishes, are of great value as reservoirs for forage min- 

 nows. They serve as feeders to the larger streams and also as rearing and 

 spawning areas for game fishes. They should be improved and protected 

 wherever possible. 



In some streams rough or undesirable fishes furnish an even greater 

 problem than in lakes. Many large streams have become so silted and 

 muddy that game fishes have become scarce and rough fishes very 

 numerous. Rough fishes are much harder to control in rivers than in 

 lakes. The open condition of running waters enables the rough fishes 

 to re-enter an area from either downstream or upstream. Where im- 

 passable dams are present, control of rough fishes becomes easier. 

 Continual removal is the only practical control and may be supple- 

 mented by encouraging the predatory game fishes. 



Warm-water streams of fishable size should be improved as far as 

 conditions warrant, with due consideration of the cost. Clean water is 

 always necessary. Undisturbed feeding and spawning areas should be 

 provided. Wherever possible, pools and sheltered areas should be created 

 and protected. With these conditions improved as much as possible, the 

 streams should be stocked with the desirable species of game and pan 

 fishes. If these fishes can become established, they may aid in reducing 

 any surplus of rough or forage fishes. 



Although fish population balances may constitute a problem in 

 streams, they are not usually as serious as in some lakes. Streams, 

 like lakes, have a limited productivity and can support only a certain 

 amount of fish, but if this amount is exceeded and competition becomes 

 too great it is usually possible for stream fishes to escape to other areas 



