512 A NATIONAL PLAN FOR AMERICAN FORESTRY 



tance of shelter in the daily life of fish is frequently not realized, 

 and yet even a casual investigation will show that ordinarily very 

 few fish are to be found where there are no hiding places near by, 

 even though other conditions may be favorable. This is especially 

 true of trout and bass, and every experienced angler knows that there 

 is no better place to cast for these fish than near an old log or a 

 tangle of submerged branches. 



Food and shelter are largely dependent on a stable environment, 

 and there is probably no way in which the forests exert a more pro- 

 found effect on fish life than in regulating the run-off thus producing 

 a regularity and permanency in lakes and streams not usually found 

 in nonforested regions. It is well known that streams with a gentle 

 current and no great or sudden fluctuations in level have a much 

 richer fauna and flora than torrential streams subject to violent 

 floods. These floods scour out the stream beds and either carry off 

 or destroy great quantities of aquatic organisms. In some instances 

 fish may be killed in considerable numbers, but it is believed that 

 ordinarily it is the invertebrates on which fish feed that suffer the 

 greatest injury. 



Following the unprecedented floods in Vermont several years ago, 

 it was found that the streams still contained large numbers of trout 

 but that insects and other invertebrates on which trout feed were 

 very scarce, and for months the fish showed every indication of par- 

 tial starvation. Severe floods may also destroy the spawning beds 

 and any eggs or fry which happen to be present. 



Extensive fluctuations in the water level also result in large num- 

 bers of aquatic organisms being left behind and destroyed as the 

 waters recede. Not infrequently fish, especially the younger stages, 

 become stranded in small pools which eventually dry up or become 

 too stagnant for their support. The evil effects of rapidly fluctuating 

 water levels are especially noticeable in the case of hydroelectric 

 developments. In most instances the construction of reservoirs for 

 power purposes would be distinctly beneficial to fish if it were not for 

 the great fluctuations in water levels which are not only destructive 

 to the food but frequently expose the eggs and fry of fish to the 

 effects of wind and sun. 



Floods and erosion go hand in hand and the resultant deposits of 

 silt frequently do immense injury to fish life either directly or indi- 

 rectly. The extent to which fish are directly injured by the presence 

 of large quantities of silt depends largely on other conditions in the 

 water and also on the species of fish concerned. Some species such 

 as catfish and carp are apparently but little affected by roily water, 

 but trout, bass, and other game fishes undoubtedly thrive best in 

 waters containing little silt. 



The greatest damage to fish from the presence of silt is undoubtedly 

 indirect. The deposition of large quantities of sediment in a lake or 

 in the bed of a stream destroys great numbers of food organisms and 

 it is not infrequent to find areas which were once rich in food now 

 changed to wastes of barren sand. In fact, there is no type of bot- 

 tom which produces less food than the shifting sands which are now 

 becoming so common in our streams and lakes as a result of defor- 

 estation and cultivation. Vegetation is buried or prevented from 

 obtaining a foothold and pools which once furnished food and shelter 

 become filled and the fish driven elsewhere. 



