433 
more than twice the all-zone river average for bottom fauna only in the 
same distance (705 Ibs.), and at more than 5% times the average 
figures for bottom fauna only in the lakes and other backwaters be- 
tween the two dams in 1914 and 1915 (255 lbs.). 
The total stocks in the entire 52,760 acres of lakes and ponds 
(acreage as with no levees, substantially same as 1908 rather than 
1914—1915, for purpose of comparison with fish yields of that year), 
76,358,400 Ibs. is more than 10 times the total stocks in the 59.3 miles 
of river opposite (6,988,103 Ibs. for 26,700 acres). Of the total, 13,- 
453,800 lbs., or 17.6%, represents the bottom animals of the full acreage ; 
and 62,904,600 Ibs., or 82.3%, represents the small weed animals of the 
upper 9 inches only, in the rather more than 50% of the total acreage 
within the 4-foot line. 
BorroM- AND WEED-FAUNA Stocks, LAKES, COPPERAS CREEK DAM TO 
LAGRANGE (59.3 MILES) 
Approx. acreage |Average valuation*| Total stocks |Per cent. 
8 ft. Havana pounds per acre | for acreage in of 
(No levees) 1914—1915 first columny total 
Bottom fauna | 
stocks—all 52,760 a. 255 13,453,800 17.6% 
depths 
Weed fauna 
stocks—1—4 29,700 a. 2,118 62,904,600 82.38% 
ft. 
Bottom and 
weed stocks 52,760 a. 1,447 76,358,400 
The Bottom- and Weed-Fauna of the Littoral Zone of the Deep 
Glacial Lakes of Northeastern Illinois, 
August—October, 1916 
1. Botrrom Fauna 
The general average of 119 mud-dipper collections from the zone 
of 1—7 feet in eight of the deep glacial lakes of northeastern Ilinois 
in August—October, 1916, was only 82.8 Ibs. per acre. The six isolated 
lakes studied (Deep, Cedar, Zurich, Crystal, Long, and Sand lakes) 
showed the better average (105.8 Ibs.), while the two large lakes (Fox 
and Pistakee) directly open to the channel of Fox River averaged only 
54.2 lbs. Sparse vegetation, principally species of Potamogeton, with 
some Chara, chiefly within the 3-foot line, were present at most of the col- 
lecting stations. The bottom varied from sand, gravel or sandy mud, to 
* soft black mud or yellow clay. On the windward side (southeast or west) 
of most of these lakes there is a more or less sterile clay zone with very 
* Based on data from 12 lakes representing around half of the total acreage. 
+ Equals approximately that of 1908. (Table originally made for comparison 
with 1908 fish yields.) 
