374 Inrtinois NAaTurRAL History SurvEY BULLETIN V ots 22, ct ris 
1941 broods of bass. “Table 5 gives the 
numbers of these fish recaptured in four 
fishing seasons since the bass and bluegills 
were placed in Fork Lake. 
These returns must be considered nearly 
“optimum” because the lake contained no 
other fish when the bass and bluegills were 
introduced, and food competition was kept 
at a minimum by constant cropping. The 
original bluegills could have suffered no 
predation from the bass as they were al- 
poor in crayfish, the bass-bluegill combina- 
tion might be improved by introducing 
crustaceans of species locally abundant. 
5. Bass and bluegills will maintain 
their numbers under intensive fishing. It 
is estimated that Fork Lake was. cropped 
to the extent of about one-half of its car- 
rying capacity for these species during the 
4 years covered by the study. 
6. In some lakes where the fishing 
pressure is light, it may be necessary to 
Table 5.—Returns from the original planting of 270 adult bluegills and 1,440 largemouth 
bass fry in Fork Lake, June, 1938. 
BLUEGILLS LarGEMouTH Bass 
YEAR Per Cent of Per Cent of 
Number Original Number Original 
Stock Stock 
1930 i aoe ae eee ene Speke 162 60.0 349 24:2 
1940 cpa Oe te ee ee aie 27 10.0 he | Tied 
194 128 Sete Rea eee ee 2 Ox7 74 Se 
194) Nd a Ane 0 0.0 66* 4°6* 
Ota ley ee feo eee 191 70.7 706 49 
* Collections from March through June plus 
ways too large to be taken. Smaller re- 
turns from the bass are undoubtedly the 
result of cannibalism during 1938 and 
1939, 
Fourteen other lakes have been stocked 
with bass and bluegills and followed as 
carefully as time would allow. The infor- 
mation from Fork Lake, and other lakes 
containing bass and bluegills, suggests the 
following points of interest in regard to 
the use of this combination: 
1. There is a marked improvement in 
fishing, especially for bass, over that fur- 
nished by mixed populations of several 
species of fish. 
2. Under moderate fishing intensity, 
largemouth bass are unable to control the 
numbers of bluegills. Therefore, in stock- 
ing a new or renovated lake, it is unneces- 
sary and possibly undesirable to stock more 
breeder bluegills than breeder bass. 
3. As bass spawn at the age of 2 years 
and bluegills at 1 year, it is better to stock 
both adult bass and adult bluegills, rather 
than adult bluegills and bass fry or finger- 
lings less than a year old. 
4. A large crayfish population was in 
evidence in several lakes where bass 
growth was exceptionally rapid. In lakes 
fish salvaged from washout. 
destroy bluegill nests, or remove substan- 
tial numbers of bluegill fry, in order to 
maintain a rapid growth of this species. 
In lakes where bass fishing is of primary 
interest, attention is being directed toward 
the use of largemouth bass alone. Ridge 
Lake, an experimental body of water of 
about 18 acres, near Charleston, IIl., has 
been reserved as a study area for this 
species. Although the bass investigation is 
less than 2 years old, its progress may be 
of some interest. The lake, built in the 
valley of an intermittent stream, began to 
fill after April 17, 1941. During May, 
100 breeder bass were stocked in about 6 
acres of water that had collected behind 
the dam. ‘These fish spawned in early 
June, and 38 broods of approximately 
2,000 fish each, or 76,000 fry, were count- 
ed. In July, 336 yearling bassi@omtom 
inches long) were added to reduce the 
number of young produced in the lake. 
All fish stocked, both as breeders and year- 
lings, were fin clipped for later identifi- 
cation. 
The growth of the 1941 brood fish 
produced in the lake has been extremely 
rapid. Collections made in October, when 
these fish were 414 months old, included 
