274 
bass caught and from most of the larger 
bluegills and used later for age analyses. 
‘The lake was closed to public fishing in 
1943 and until August in 1944. 
3. At intervals of 2 years, beginning 
in 1943, the lake was drained in early 
spring < and a census was made of the fish, 
table +. Five censuses were made in the 
1941-1951 period covered by this study. 
After each census, the large bass (mini- 
mum length 10 inches in most years, 8 or 
9 in others) were marked by fin-clipping 
and returned to the partially refilled lake 
basin, table 5. After each draining, ex- 
cept that of 1949, the lake basin had com- 
pletely refilled before the beginning of the 
summer fishing season. In 1949, the basin 
had only partially refilled; the water cov- 
ered an area of about 11 acres on June 1 
and remained practically constant in area 
until November. 
4. No stocks of fish, other than the 
435 bass released in 1941, the 129 blue- 
gills released in 1944, and the 138 war- 
mouths released in 1949, were introduced 
into Ridge Lake from other bodies of 
water. In the study period, which began 
in the spring of 1941 and ended after the 
bass spawning season but before the an- 
gling season of 1951, more than 11,000 
bass and 154,000 bluegills were perma- 
nently removed from the lake by angling 
and in draining censuses, table 3. Of 
these, 3,743 bass and about 9,000 bluegills 
were taken by anglers; the others were 
taken in draining operations as excess small 
fish. In the 1949-1950 period, few war- 
mouths were caught by anglers and less 
than 1,000 were taken in the 1951 draining 
census, table +. About 3,500 fish other 
than bass, bluegills, and warmouths were 
taken from the lake (mostly in draining 
operations) during the study period, table 
3. These, which included green sunfish, 
black bullheads, yellow bullheads, carp, 
and a black buffalo, were of species in- 
digenous to Dry Run Creek and the Em- 
barrass River. Although large numbers of 
bass and bluegills were removed from 
Ridge Lake during the study period, these 
fish were as numerous in Ridge Lake in 
1951 as they had been at any other time 
during the 10-year period, table 4. 
5. The weight of bass taken in the five 
draining censuses ranged from 31.5 pounds 
per acre in the 1947 census to 50.4 pounds 
[LtiNois NATuRAL History Survey BULLETIN 
Vol. 26, Art. 2 
per acre in the 1949 census, table 7. In 
three censuses, those of 1943, 1949, and 
1951, the weight of bass was 48.2, 50.4, 
and 49.9 pounds per acre, respectively. 
‘These poundage calculations suggest that 
the carrying capacity of Ridge Lake for 
bass may be about 50 pounds per acre. 
Once the bluegill population had become 
well established in Ridge Lake, poundages 
per acre of bluegills varied between 86.9 — 
and 193.3; the largest poundage of bass 
was found with the smallest poundage of 
bluegills (1949 census) and the largest 
poundage of bluegills with the smallest — 
poundage of bass (1947 census), suggest- 
ing interspecific competition, | 
6. Yields of bass taken by angling dur- — 
ing years in which the lake (an 18-acre 
area assumed) was open to public fishing 
varied between 10.9 and 30.0 pounds per 
acre, table 8; yields of bluegills varied be- 
tween 6.2 and 45.9 pounds per acre. Fish- 
ing pressure ranged from 90 man-hours 
per acre in 1944 to 320 man-hours per — 
acre in 1948, table 18. 
7. Estimates of numbers of bass fry — 
were made during the spawning season of — 
each year, 1941 to 1951, inclusive, table — 
9. In years in which the lake was drained 
and small fish were removed in March, 
the estimates of numbers of fry varied 
between 18,000 and 116,000, with an 
average of 50, 500. In years in which the 
lake was not drained in: Mareheaan small — 
fish were present, the estimates of num-— 
bers of bass fry ranged from 0 to 26,000, 
with an average of 5,900. Schooling bass © 
fry were observed prior to June 1 in only 
3 years out of 11. z 
8. There was no apparent relationship E 
between the number of bass of spawning — 
age in the lake in any given season and © 
the number of bass fry produced i in that” 
season, table 10. Years in which small 
fish were abundant in the lake (particu- 
larly those years in which many small blue- — 
gills were present) were years of low — 
production of bass fry. 
9. The ratios of numbers of bass 
fry of a brood to individuals of the same — 
brood taken as larger fish in the 21 months — 
after spawning varied between 29 to 1 and 
40 to 1, in 1941, 1943, 1947, and 1949, 
table 11.. In 1945, when the number of 
bass fry produced was unusually large, 
the survival ratio was 195 to 1. 
a oe a a oo 
