RELATIVE NUMBERS OF DIFFERENT SIZES OF 
BEAGK CRAP Pd ES 
IN HORSESHOE LAKE 
1934 
SURVEY 
GINAL 
NO SURVEY MADE IN 1935 
1936 
SURVEY 
ORIGINAL STOCK 
1937 
SURVEY | 
ORIGINAL STOCK 
| 
1938 
SURVEY 
LENGTH IN INCHES 
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state. Near Horseshoe Lake this water left the 
channel of the Cache to enter the Mississippi at Dog 
Tooth Bend. At the time of the flood it seemed likely 
that Horseshoe Lake might have lost a large part of 
its fish or that objectionable species might have 
moved in. The 1937 survey was made to determine 
Left.—The black crappie made up 37 percent of all fish 
taken in hoopnets by the four surveys, 1934-1938. A huge 
brood of black crappies was spawned in the spring of 1932 
from breeding stock placed in the lake a few months earlier. 
This brood grew at a normal rate during its first two years, 
reaching an average total length of 6 inches by the spring 
of 1934. After that, growth was retarded by dwindling 
food supplies. These fish reached an average length of 
8 inches by 1936 and since then have not grown at all. 
Moderate reductions in the numbers of this 1932 brood from 
year to year have not resulted in increased growth among 
the survivors because of increasing competition by the 
white crappies. The black crappie, more than any other 
fish, has been responsible for destroying the young, not 
only of its own kind, but also those of most other species 
in the lake. 
what changes the flood had made. We found no evi- 
dence that Horseshoe Lake had lost any of its fish. 
The only intruders were two spotted gars. Up to this 
time this species had not been taken in the lake, 
although it is present below the spillway. No spotted 
gars or other newcomers were caught in this spring’s 
survey. If this flood had taken place in warm 
weather when fish are active, it seems certain that 
the fish population of Horseshoe would have been 
greatly disturbed and mixed up. Throughout the 
early part of the flood, the quieter waters were cov- 
ered with ice and at no time did the temperature rise 
more than a few degrees above freezing. It appears 
that the fish of Horseshoe and vicinity lay quietly 
while the flood waters rose and went down again. 
LARGEMOUTH BLACK Bass 
Two of the diagrams show the essential facts about 
the largemouth bass in Horseshoe Lake. 
When the lake was visited in May of 1932, as 
many as a quart of Gambusia could be taken in a 
short haul with a minnow seine, together with bass 
fry about an inch long and large numbers of fry 
of the flier sunfish. The top minnows and the fry 
of the flier sunfish probably made up the bulk of 
the food of the bass that first year and were responsi- 
ble for their rapid growth. When the lake was 
visited in the summer of 1933 it was noted that the 
bass were growing very rapidly. The decline in the 
LARGEMOUTH BLACK BASS 
L) Av. oF ALL DATA (ILL.WIS.,NEBR..LA) 
AV. OF 328 FROM HORSESHOE LAKE 
LENGTH INCREASE IN INCHES 
ass 
INN 
7 MM 
Z 
lp Ne O eel 
3RD 4 5TH 6TH 7TH 8TH OTH IOTH 
YEAR OF eS Lz 
After Horseshoe Lake was rebuilt, food was at first abun- 
dant. The bass responded to this favorable condition more 
readily than other species and grew very rapidly. At an 
age of one year they were almost twice as long and weighed 
six times as much as the average yearling bass in the 
Mississippi Valley. Increasing competition by crappies re- 
duced growth in the bass to normal in their second year, 
then below normal, finally almost to zero. At the present 
time these bass are living on a subsistence basis. 
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