240 
manently removed from the lake during 
the 1941-1950 period by angling (yield) 
and of those permanently removed in the 
1943-1951 draining censuses (culling op- 
erations) are shown in table 3. Not in- 
cluded in figures for the draining censuses 
were fish, less than a year old, so small 
that accurate counts of them were not 
possible. In 1941 and 1943, the lake was 
not opened to the public, and the angling 
records for both years are those of Natural 
History Survey personnel who were tak- 
ing samples of fish for growth studies. 
Many additional bass were taken by Sur- 
vey personnel and released alive in 1941 
and 1943; those listed in table 3 were 
fish so severely hooked as to make their 
survival uncertain. 
The fact that, from original stocks of 
only 435 bass and 129 bluegills, more 
than 11,300 bass and more than 154,000 
bluegills were removed from Ridge Lake 
during a 10-year period of operation is 
good evidence that both species are ca- 
pable of expanding their populations to 
approach the carrying capacity of waters 
into which they are introduced and of 
maintaining these populations indefinitely 
Intinois NatuRAL History Survey BULLETIN 
Vol. 26, Art. 2 
under a system of operation such as has 
been followed at Ridge Lake. In this 
experiment, the bluegills showed a higher 
reproduction rate than did the bass. Other 
species, primarily black bullheads and 
green sunfish, were able to survive and 
in some years to increase their numbers 
under the predation pressure of a strong 
bass population. 
Whereas table 3 lists the numbers and 
weights of fishes permanently removed 
from the lake by angling and in the 
draining censuses, table 4+ lists the num- 
bers and weights of fishes taken in these 
draining censuses and table 5 lists the 
numbers and weights of fishes returned 
to the lake following the censuses. Both 
tables + and 5 are arranged to show data 
on the individual fin-clip groups of large- 
mouth bass and bluegills for each of the 
five censuses in which they were involved. 
Green sunfish, bullheads, and other in- 
digenous fishes, removed from the lake on 
each census, and also introduced war- 
mouths, have been separated in the census 
tabulations, table 4, into “large” and 
“small” categories. Any green sunfish or 
warmouth of 6 inches or more in length 
Table 5.—Largemouth bass and bluegills returned to Ridge Lake following each of five 
draining censuses. Fish were separated into groups on the basis of previous fin markings or 
lack of such markings. 
1943 Census | 1945 Census 
Group 5} ain 5 on 
2 rate 2 eo] 
5 SE, = | SE 
eo ee Noe eee 
Bass 
1941 stock...... 15 | 47.90 9 | 35.08 
1941-1942...... | 1,973* 1336.90! 496 |379.59 
1943-19447... .. ee 142 101.13 
1945-1946...... — — — — 
1947-1948... ...| — | — — — 
1949-1950...... ch Ey a es — — 
ROW) Se ions a eo 1 908 1364-60 647 \515.80 
Per acre........| 110 | 21.4 S644 2857 
BLUEGILLS 
1944 stock......| — — 61 | 25.74 
1944-1946...... — — — — 
1947-1948...... oe — — — 
1949-1950...... i — |-— aes — 
ft Ae eo ee puss OL W574 
Per acre........) — [ee 3 1.4 
1947 Census 1949 Census 1951 Census 
S | #9 | 38 | 23° 
eg | is g bE E bE 
2! v = 
Pa ze cA Ze Z. Ze 
Te a 1:| 70081 se eS. 
61 1148.95 931 OU Te 31 14.90 
20 | 48.33 9 | 33.46 2\ ome 
310 |283.12 77 1201.74 9| 36.10 
wes Ns 917 1471.49 | 170 | 335.05 
oe tx ae fits 619 | 367.15 
392 \487.15 | 1,027 |804.86 | 803 | 762.29 
22 | 27.1 57 | 44.7 45 | 42.4 
5 ame eee m0 pis pe 
1,759: 283) 95-| = = i E.. 
ee a ie La 656 | 130.82 
1,761 |@84.10| — = 656 | 130.82 
98 | 15.8 oe = 36.) 
* Figure includes estimated 473 bass weighing estimated 80.41 pounds that escaped the 1943 census. 
2 Some of the fish of this group were spawned 
in 1941 or 1942, escaped the 1943 draining census, and appeared as — 
unmarked fish in the census of 1945, when they were given the same mark as the fish spawned in 1943 and 1944. 
