30 U. S. BUREAU OF FISHERIES, 
feet wide) was not deeper than the 200-foot strips alongshore. The 
zones near shore are by no means equally productive throughout, the 
more densely populated portions manifesting definite relations to the 
position of the channel and to other features sof the stream, especially 
those that affect the stability of the bottom. Productive areas usually 
occur in parts of the shore strips that are bathed by the current, or 
where the channel approaches the shore. Character of bottom soil is 
a significant feature, but this is often controlled by current, topog- 
raphy, and other conditions. 
Keokuk Lake, formed in the Mississippi River above the dam at 
Keokuk, has been examined some years after its formation to de- 
termine some of the effects of the changed conditions. A report of 
the observations is in process of preparation, 
STUDIES OF INLAND LAKES. 
The Bureau has continued to cooperate with the Geological and 
Natural History Survey of Wisconsin in biological and chemical in- 
vestigations directed at the fundamental problems of the capacity of 
inclosed waters for support of fish life. As has hitherto been stated, 
the Bureau bears only a relatively small proportion of the expense of 
the investigation. Substantial progress has been made, as is indicated 
by the following outline submitted by President Edward A. Birge 
and Chancey Juday representing the State Survey: 
1. The bulletin dealing with the quantity and chemical composition of the 
plankton of the lakes situated in the vicinity of Madison is now ready for the 
press. During this investigation 481 observations have been made on the net 
plankton and 182 on the nannoplankton of these lakes, making a total of 663 
eatches. These catches were combined into 374 samples for the chemical 
analyses. About 2,500 separate chemical and ash determinations have been 
made on these samples and 52 samples of special material obtained during the: 
progress of this work. 
The quantity of dry organic matter in the total plankton of Lake Mendota 
(net plankton plus nannoplankton) varied from a minimum of 230 pounds per 
acre in February to a maximum of 521 pounds per acre in December in the area 
situated within the 20-meter contour line. When the surface of the entire lake 
and the volume are taken into account the range is from 126 pounds per acre 
in February to 256 pounds in December. The live weight of the organic matter 
is 10 times as much as the dry weight. 
Of the dry organic matter an average of 44.5 per cent consisted of crude 
protein, 7.5 per cent ether extract, and 5.8 per cent crude fiber, leaving 42.7 per 
cent to be designated as nitrogen free extract (chiefly carbohydrates). The 
pentosans were the only carbohydrates studied, and they constituted an average 
of 4.6 per cent of the organic matter. 
Lakes Monona and Waubesa yielded larger quantities of total plankton. The 
amount in the former varied from a minimum of 276 pounds per acre in July to 
a maximum of 1,063 pounds of dry organic matter in October in the area 
bounded by the 20-meter contour. For the entire lake the range was from 111 
pounds to 426 pounds per acre of surface. The maximum crop of plankton in 
Lake Waubesa yielded 862 pounds of dry organic matter per acre in the area 
bounded by the 10-meter contour, or 415 pounds per acre for the entire lake; 
the average for 16 samples is 216 pounds of dry organic matter per acre. 
The dry organic matter in the total plankton of Lake Monona contained 57.5. 
per cent of crude protein, 4.8 per cent of ether extract, 4.7 per cent of pen- 
tosans, and 4.4 per cent of crude fiber. The total plankton of Lake Waubesa 
yielded an average of 48.6 per cent of crude protein, 4.6 per cent of ether ex- 
tract, 5.8 per cent of pentosans, and 4.4 per cent of crude fiber. 
2. Mr. Wilson’s numerical results for the bacteria of Lake Mendota show 
that the average number from surface to bottom in 23.5 meters of water was 
3,000 per ¢c. c. of water in July and August, 1919; in the following autumn and 
