for stocking new artificial lakes and farm ponds, These lakes proved superior to fish hatcheries 
as sources of fish because they supplied hardier fish of breeding age at less cost, 
The number of the various species of fish taken per acre from Lake Chautauqua and 
Spring Lake by the Department of Conservation is given in table 8, Assigned values of fish for 
stocking purposes are based, in the case of bass, upon their sale price by private sources and, 
in the case of other fishes, upon their food value, The value of the stocking fish taken'from Lake 
Chautauqua is only slightly above the cost of procurement to the Department of Conservation, 
The value of Lake Chautauqua to the state for obtaining stocking fish was calculated to be $1.18 
per acre of water per year; of Spring Lake, $9.68 per acre-year, 
Fig. 7.--Many marshes in Illinois return considerable revenue from the 
trapping of muskrats, The muskrat houses shown here are in a marsh smartweed 
bed, Rice Lake, near Banner, 
FUR YIELD 
The value of riverbottom lakes for muskrats, the principal furbearers, is regulated by 
the stability of water levels and the abundance of river bulrush (Scirpus fluviatilis), marsh smart-= 
weed (Polygonum muhlenbergi), fig, 7, and, to a much lesser extent, American lotus (Nelumbium pentapetalum) 
(Bellrose & Brown 1941), River bulrush and marsh smartweed occur on about 15 per cent of 
the water areas of the Illinois River valley and American lotus on an additional 10 per cent, 
18 
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