72 
BULLETIN OF THE BUREAU OF FISHERIES. 
line it is reduced by an amount equivalent to the alkalinity; that is, where free 
carbon dioxide in the analysis is marked ( — ) it signifies that the half-bound carbon 
dioxide lacks the number of cubic centimeters indicated of being equal to the fixed 
carbon dioxide. Where the free carbon dioxide is marked ( + ) , it indicates that 
the water is acid to phenolphthalein and that free carbon dioxide is present in 
excess of that combined as fixed and half-bound in acid carbonate. 
The algae are able to use the free carbon dioxide and a very large proportion 
of the half-bound, but not the fixed carbon dioxide. There is usually little free 
carbon dioxide in the epilimnion, where the largest part of the algae thrive. They 
are therefore largely dependent on the acid or half-bound carbon dioxide for their 
supply. If the water is soft, it contains less carbon dioxide, and this limits the 
growth of algae. 
In shallow lakes of Group I, where the whole body of water is circulated by 
the wind, the softness of the water does not limit the carbon dioxide supply of the 
algae to any great extent, because the carbon dioxide furnished by decaying organic 
material at the bottom is soon circulated and used by the algae. 
It appears also that the nitrogen content of the water plays an important 
part in the growth of algae. The lakes that contain the largest percentage of nitro- 
gen as nitrates, nitrites, and ammonia support a larger growth of algae. In other 
words, these plants need fertilizer the same as land plants. This nitrogen is largely 
supplied from the drainage basin. If this basin is inhabited, cultivated, and fertil- 
ized, more fertilizer will be washed into the lake from it than from a wild, unsettled 
area. 
FISH IN SMALL LAKES IN WASHINGTON AND IDAHO. 
From Tables 7 and 8 (pp. 77 and 97) it will be noted that a large number of 
small lakes have been examined. In many cases these were the lakes in which 
the game wardens and sportsmen seemed to be the most interested, and they were 
anxious to have taken us to many more if time had permitted. 
Many of these lakes — for instance, Chaplain, Cottage, Cow, Martha, Padden, 
Paradise, and Silver, in western Washington, and Chatcolet, Deer, Loon, Liberty, 
Newman, Silver, and Twin, in eastern Washington — were originally trout lakes. 
To-day trout are occasionally caught in some of them. Others of them (Chaplain, 
Deer, Chatcolet) still offer fairly good trout fishing. In some there is practically 
no fishing, and many have been stocked with bass, for which the lakes seem to be 
especially well adapted if we judge from the large number caught a few years 
after planting. Chatcolet, Clear, and Cow Lakes are good bass lakes to-day. In 
Twin Lakes the trout have been replaced by perch. 
If the depth, temperature, oxygen, and plankton of these lakes are compared 
with those of Wisconsin lakes, there is no marked or general difference, so bass 
and such fish should thrive. Probably trout would still live in the lakes, adapting 
themselves to conditions now found, if the lakes were not fished, but it must not 
be assumed that the conditions to-day are' the same as when the trout thrived in 
these lakes. 
Formerly most of these lakes were surrounded by virgin forests. The smaller 
ones were partially protected from the sun, and their inlets were largely shaded 
