96 
The First Food of the Common White-Fish. 
existence. Disturbances of the natural balance of life, of the 
primitive and spontaneous system of reactions by which the dif- 
ferent groups of organisms are related, will therefore be unusually 
serious and lasting; and where such disturbances result from 
human interference, as by the yearly capture of large numbers of 
any important fish, it is especially desirable that artificial means 
of compensation be taken to restore the disturbed balance as 
nearly as possible. Excessive loss will be made good by natural 
reactions far more slowly than if it occurred to a pond or river 
species, accustomed, as most of the latter are, to fill up rapidly 
enormous gaps in their numbers. 
On the other hand, to multiply unduly by artificial measures any 
species naturally abundant in such a lake, will have scarcely a 
less disturbing influence than to dimmish its numbers in the same 
ratio. The relatively nice balance between the demand for food 
and food supply which here naturally obtains, is such that an ex- 
traordinary increase in a species must soon react to diminish 
greatly its food resources — a fact which will then take elfect on 
the species itself, reducing it below its natural, original level; 
and if. both excessive capture and excessive multiplication go on 
side by^side we shall have this result finally aggravated to an ex- 
treme degree. 
As fishes are caught before the end of their natural lives, but 
planted by the fish culturist when young, it is evidently the food 
of the young which will be first and most seriously alfected by 
over-production. Only a part of the adults, perhaps a small frac- 
tion, will live a life of ordinary natural length, many being cap- 
tured before they have attained even the average size; but a far 
greater number, perhaps nearly every one, must survive the earli- 
est period and must consequently draw most heavily upon the 
earliest food resources of the species when these differ from those 
of the adult. 
The above considerations are brought forward here to show the 
especial importance, to us, of a study of the system of natural 
interactions by which the animals of our great lakes affect each 
other, if we would avoid the necessarily injurious consequences of 
our own interference with the natural order there obtaining, and 
above all to show the extraordinary value of a knowledge of the 
food habits and food capital of the young. They apply perhaps 
