Largemouth Bass in Ridge Lake, 
Coles County, Illinois 
Ridge State Park, Coles County, 
Illinois, was completed, it was set 
aside as a study area for the _large- 
mouth bass, Micropterus salmoides (Lacé- 
pede). Initially, the largemouth was the 
only species of fish involved in the study. 
Later, in 1944, the bluegill, Lepomis 
macrochirus Rafinesque, was added as a 
companion species for the largemouth, and 
in 1949 the warmouth, Chaenobryttus 
coronarius (Bartram), was introduced. 
At the time the study was begun, little 
was known of the factors that control the 
numerical size of populations of the large- 
mouth, or the maximum total poundage of 
this species that a lake or pond could sup- 
port. Extensive censusing of pond fish 
populations was in progress in various 
parts of the United States, and some fish- 
eries investigators (Meehean 1942: 193; 
Swingle & Smith 1941:274; Swingle 
1950: 14) assumed that, because in many 
ponds the total weight of largemouth bass 
exhibited relationships to the total weight 
of prey fish present of, say, 1 to 3 or 1 to 
4, such relationships represented the 
“normal” or optimum ratios. These in- 
vestigators further assumed that such ratios 
should be duplicated as nearly as pos- 
sible in stocking new ponds. 
The hypothesis of ‘“normal”’ ratios be- 
tween the weight of largemouth bass 
populations and the weight of populations 
of prey fish coexisting with the bass was 
based partially on the assumption of a 
direct predator-prey relationship between 
the two groups of fishes. Seemingly logi- 
cal at the time was the further assumption 
that growth in a population of large- 
mouths cannot remain “normal” if the 
population of prey fish drops below a cer- 
tain predator-prey ratio. Both of these 
assumptions had to be discarded when re- 
search demonstrated that largemouths, 
once defined as piscivorous, are in fact 
[: 1941, when Ridge Lake, in Fox 
GEORGE W. BENNETT 
relatively omnivorous and are able to 
maintain populations at high numerical and 
poundage levels when species of fish be- 
lieved to furnish their principal sources 
of food are not present. In several arti- 
ficial ponds in Illinois, largemouth bass 
populations isolated from other fishes main- 
tained high numerical and poundage levels 
(Bennett 1951: 235, 239 and unpublished 
records). Conversely, in some Illinois 
ponds in which largemouth bass were 
coinhabitants with other species of fish, 
the bass populations dwindled in both 
numbers and poundages. 
In early decades of the present century, 
the phenomenon of declining populations 
of largemouth bass, a phenomenon early 
appreciated by fisheries personnel of the 
period, was largely responsible for the 
extensive development of hatchery propa- 
gation of these bass and for the imposi- 
tion of certain fishing restrictions, includ- 
ing a closed season, a 10-inch minimum 
length limit, and a creel limit of 10 fish, 
first put in force in Illinois on July 1, 
1923. 
Fisheries workers in Illinois have ob- 
served often the ability of largemouth 
bass to expand their populations suddenly 
to take advantage of new territory. A 
new impoundment is particularly favor- 
able to the successful reproduction of 
largemouths (Bennett 1946:9). When, 
for example, a new reservoir is stocked 
with equal numbers of adult largemouths, 
white crappies or black crappies, bluegills, 
and black bullheads, usually the large- 
mouths, during the first spawning season, 
populate the shore shallows with tre- 
mendous numbers of young. Throughout 
this first season, the young of the other 
species of fish included with the bass may 
be so few in number that none can be 
collected. Probably few workers who have 
observed this sudden population expansion 
of bass have recognized its true signifi- 
E217] 
