270 
removed prior to the bass spawning season. 
In some of the years in which many small 
bluegills were present, only a very small 
number of bass fry could be found; in 
others, none at all. The high sustained 
yield of bass at Ridge Lake was a result 
of successful natural reproduction and 
satisfactory survival of young bass every 
other year. There was little relationship 
between the number of spawners and the 
number of fry they produced, table 10; 
there was an inverse relationship between 
the number of bass fry and the number of 
small bluegills in the lake at spawning 
time. 
The key to successful management of 
largemouth bass in Ridge Lake has proved 
to be the control of the numerical size ot 
the populations of fishes other than bass 
that inhabit the water. If bass in other 
waters are similarly influenced by popula- 
tions of other fishes, it is doubtful if closed 
seasons, length limits, and creel limits, 
which have been relied upon for many 
years to protect and enhance bass popu- 
lations, have been of any value. The 
minimum length limit of 10 inches, the 
creel limit of 10, and a closed season of 
March 1 to June 15 were first introduced 
into Illinois in 1923. There is no evidence 
that these fishing regulations have had any 
influence on bass fishing in the state. 
Ridge Lake was not opened to public 
fishing in any year until after the bass 
spawn had been observed or the adults 
were spent (in a year in which no spawn 
was seen), so that bass that were spawn- 
ing in the lake always were protected from 
human interference. In years when many 
small fish were present in Ridge Lake and 
bass spawn production was very low 
(1944, 1946, 1948, and 1950, table 10), 
the opening of the lake to intensive angling 
during the bass spawning season could 
have had no measurable effect upon the 
production of young bass. In years when 
small fish were removed from Ridge Lake 
in March prior to the bass spawning 
season and the bass spawn production was 
high (1943, 1945, 1947, 1949, and 1951), 
it would have been difficult to measure 
accurately the effect of heavy angling, 
during the bass spawning season, upon 
the production of young bass. Judging 
from the behavior of bass in response to 
public fishing at Ridge Lake, however, I 
Intinoris NatruraAL History SurRvEY BULLETIN 
Vol. 26, Art. 2 
believe that the total effects of fishing 
(removal of some spawning fish and the 
frightening of spawning and nest-guard- 
ing fish) would be less of a limiting factor 
in the production of young bass than 
would be the nest-robbing activities of a 
large population of bluegills. 
Estimated survival rates for bass fry 
in the years 1941, 1943, 1947, and 1949 
were 29 to 1, 40 to 1, 30 to 1, and 34 to 
1, respectively, table 11. At these rates of 
survival, the number of fry needed to re- 
place the adults caught by fishermen at 
Ridge Lake in any single year would prob- 
ably vary between 5,000 and 20,000. A 
few males bringing off successful hatches 
of fry would supply several times either 
of these numbers. Thus, unless fishermen 
were able to locate all of the nesting male 
bass in the lake and make a systematic 
effort to catch them, some males guarding 
nests would escape and bring off hatches 
of young in numbers more than adequate 
to replenish the population. 
The purpose of a size limit on any 
sport fish is to allow individuals to reach 
sexual maturity and spawn, but, unless it 
can be shown that a large number of 
spawners produce greater numbers of 
young than a small number of spawners, 
there is no logic in holding to a minimum 
length limit. Most species of fish in some 
measure influence the survival of their 
own young; that is, when populations are 
high the success of spawning is low, and 
vice versa. Thus, if small “yearling” fish 
(fish spawned the previous year) of a 
species are taken by anglers without regard 
to size, the survival of current-season 
young of that species may be greater than 
if the “‘yearling” fish are not cropped. It 
seems reasonable to assume that, had fish- 
ermen been allowed to take bass of less — 
than 10 inches in 1942, survival of the 
spawns of 1942 and 1943 would have 
been higher than they were. 
The only point that can be made in 
favor of a creel limit of 10 bass is that on — 
certain very infrequent occasions bass lose 
their usual wariness and bite very readily. 
On these occasions, a limit of 10 fish may 
prevent an overenthusiastic fisherman from 
taking more fish than he can use. 
A characteristic of the largemouth bass’ 
that greatly simplifies management is the 
fact that it spawns somewhat earlier than 
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