November, 1954 
and northern Illinois are more fertile 
and many in southern Illinois are less 
fertile (Bennett 1943:361 and unpub- 
lished fish censuses of ponds and lakes). 
Comparisons of the mineral analyses of 
the water of several Illinois lakes, and the 
poundages of fish these lakes support, with 
‘measurements of soil fertility on the 
watersheds show that a large part of the 
nutrient materials of each lake may have 
entered the lake with runoff water from 
the watershed and become trapped within 
the basin. A part of these materials may 
be buried under silt deposits. In addition 
to the nutrients that enter from the water- 
shed, there is within the lake itself an 
accumulation of organic materials result- 
ing from the death and disintegration of 
plants and animals, all of which adds to 
the fertility. More nutrients and organic 
matter are gained through inflowing 
water and through accumulation than are 
carried away in overflow, and thus im- 
poundments, many of which are built over 
soils of comparatively low fertility, tend 
to become more fertile as they age. 
Table 1 shows two partial mineral anal- 
yses of water made by the _ Illinois 
State Water Survey: one of the water of 
Dry Run Creek prior to impoundment 
and a similar one of lake water after im- 
poundment. A comparison of these two 
analyses shows large differences in the 
Table 1.—Partial mineral analysis of water 
from Dry Run Creek, April 7, 1938, prior to 
impoundment, and of water from Ridge Lake 
soon after gate valve was closed, April 22, 
1941. 
Dry Run 
CREEK, Ripce Lake, 
MINERAL Apri 7, 1938, |Aprit 22, 1941, 
PARTS PER PARTS PER 
MILLIon MILLION 
MEO eye o 3 2.0 Be 
Manganese..... 0.0 0.5 
Sigh. ee DAO 9.5 
@alcium...:.... 5.9 Te 
Magnesium..... 24.3 22.9 
Sodium and 
potassium.... 59.6 11.0 
Sulfate:2..-.<-: 18.5 40.1 
Nitrate........ | 1a if 
Chloride....... 5 5.0 
Methyl orange 
alkalinity..... 220.0 248.0 
Total hardness. . 113.0 272.0 
BENNETT: LAaRGEMOUTH Bass IN RipGE LAKE 227 
amounts of almost all of the minerals. 
These two water samples were taken ap- 
proximately 3 years apart, and during this 
length of time changes may have taken 
place in land use within the watershed, 
opening up new areas to erosion and 
leaching. 
A study of Ridge Lake (Stall et al. 
1951:24-5) showed that a large part of 
the sediment deposits of the lake origi- 
nated probably from the Hennepin gravelly 
loam which occurs on the steep, heavily 
eroded slopes of the watershed. These de- 
posits contain amounts of potassium and 
phosphorus adequate for farm crops, but 
they are low in nitrogen. 
The soils of the flat uplands of the 
Ridge Lake watershed are planted usually 
to row crops—corn and soybeans. ‘These 
soils are much less fertile (judged on the 
basis of the crops they produce) than are 
most of those farther north in Illinois; 
while the northern soils average a corn- 
production rate of approximately 75 
bushels per acre, those in the region of 
Dry Run Creek average not more than 
25 bushels per acre. 
Growing Season for Fishes.—In 
experiments with largemouth bass, Markus 
(1932:210) found that the rate of di- 
gestion was very slow in fish held in 
water below 50 degrees F., but that it 
increased rapidly with increasing tempera- 
tures up to about 72 degrees F. Obser- 
vations on growth of the largemouth bass 
in Illinois ponds indicate that growth 
begins each spring when water tempera- 
tures range between 50 and 60 degrees F. 
Average water temperatures at the 4-foot 
depth in Ridge Lake in 1942, fig. 5, first 
exceeded 55 degrees F. during the week 
of April 13-19 (April 15) and did not 
again drop to 55 degrees F. until the week 
of October 27—November 2 (October 
29). These temperature readings showed 
that the growing season for bass at Ridge 
Lake was nearly 6.5 months long in 1942. 
Similar measurements of water tempera- 
tures in Fork Lake (Bennett, Thompson, 
& Parr 1940:13, 15) in 1939 showed 
that the growing season in this pond was 
6 months. The site of Fork Lake, which 
lies within 65 miles of Ridge Lake, is 
only about 25 miles farther north, and its 
seasonal cycle of temperatures probably 
is comparable to that of Ridge Lake. 
