412 
than one two-hundredth of the rate between Copperas Creek dam and 
Havana. 
Figures for the total stocks present in the combined channel and 
shore acreage below Chillicothe July—October 1915 (table, p. 18), based 
on these all-zone weight valuations and on approximate acreages for 
average July—October levels in 1910—1914, show that out of total stocks 
equaling 6,988,103 pounds for about 26,700 acres, 92.7 per cent., or 
6,480,952 pounds, were in the 60.5 mile section of river above Havana— 
this constituting only one third of the total length of river studied and 
less than one third of the total river acreage. Again, of the total bottom- 
fauna stocks 53.9%, or 3,770,200 pounds, were in the 16.8 miles of river 
between Copperas Creek and Havana—which comprises less than one 
tenth of the total distance between Chillicothe and the mouth, and only 
about one twentieth of the total acreage. The stocks between Havana 
and Lagrange, 396,880 lbs., for 42.5 miles, made up but 5.6% of the 
grand total; and those between Lagrange and Grafton, 110,271 Ibs., 
for 77.5 miles, only 1.5 per cent. 
Borrom Fauna, ILLInois River, 1915. ACREAGE-WEIGHTED ALL-ZONE AVERAGES 
. POUNDS PER ACRE 
Approx. acres Estimated Bottom 
Reach Mil Gage, 8 ft part of fauna 
HESS Havana (total underIbs. per acre 
7 ft. deep | (average) 
Chillicothe to Copperas Creek 43.7 10,268* 1/3 264 
dam 2 807 
Copperas Creek dam to Havana 16.8 1,400 1/4 2,693 
89 
Havana to Lagrange 42.5 4,510 1/5 88 
58 
3 ’ 
Lagrange to Grafton (HG 10,603 2/5 10.4 
7d 
Chillicothe to Grafton 180.5 26,782 ane 261 
"252 
Average Chillicothe to Copperas Creek dam, 555 Ibs. * 
Average Copperas Creek dam to Lagrange, 705 lbs. 
2 
ov. COMPOSITION OF THE BOTTOM FAUNA 
____In the section of river above Lagrange dam, both in the channel and 
in the shore zones, the great bulk of the bottom-fauna poundages was 
made up of Mollusca (Gastropoda and Sphaeriidae), the percentages by 
* Includes Peoria Lake. 
+ The Italic figures give the number of coJlections. 
