114 College of Forestry 
CHAPTERIII. BIOLOGICAL VALUATION OF THE 
LAKE; A STUDY IN PRODUCTIVITY: 
A. HISTORICAL REVIEW. 
The scientific study of the food relations of fresh water 
animals has occupied man’s attention for a comparatively 
short time, and the realization of the intimate relation 
between the entire environment and any one group of animals, 
as the fishes for example, is of quite modern origin. As 
long ago as 1880, Dr. 8. A. Forbes (1880, p. 19), writing 
on the important question of the food of fishes, said: ‘‘Doubt- 
less, of all the features of the environment of an individual, 
none affect it at the same time so powerfully, so variously 
and so intimately as the elements of its food. Even climate, 
season, soil and the inorganic circumstances generally, 
influence an animal through its food quite as much as by 
their direct action. It is through the food relation that ani- 
mals touch each other and the surrounding world at the 
greatest number of points; here they crowd upon each other 
the most closely, at this point the struggle for existence 
becomes sharpest and most deadly; and, finally, it is through 
the food relation almost entirely that animals are brought in 
contact with the material interests of man. Both for the 
student of science and for the economist, therefore, we find 
this subject of peculiar interest and value.” 
A. J. Pieters (1901, p. 59), writing on the plants of Lake 
Erie, makes the following significant statement: “ As has 
been pointed out by both Reighard and Ward, a complete 
knowledge of the life of a fish can only be obtained by a study 
of the entire chain of biological relations existing in lakes 
and streams. In this chain plant life constitutes an import- 
ant link. Plants stand between animal life and the inorganic 
substances it is unable to use. All aquatic animal life is 
ultimately dependent upon plants, which transform carbon, 
nitrogen and other inorganic substances into organic com- 
pounds fitted for animal use. Directly or indirectly, then, 
plant life is necessary to the support of the fishes in our lakes 
