TABLE 7.—Comparison of standing crops of blue 
gills and largemouth bass in kilograms per hectare after two grow- 
ing seasons in our ponds with standing crops measured in a cross section of other unfertilized Illinois waters. 
Bluegill Largemouth Bass 
pre eee EE eee 
Average 
EE 
Number Average Number Average 
Size of Ponds Per Hectare of Ponds Per Hectare 
Location (Hectares) Source or Years (Kilograms) or Years (Kilograms) 
Our ponds 0.4 6 246.3 6 Wiest 
Dundee ponds 0.4 Buck & Thoits (1970) 4 140.5 11 84.4 
Hansen’s ponds 0.34 Hansen et al. (1960) 3 188.3 3 78.5 
Arrowhead Pond 1.05 In Bennett (1971) ase 117.6 3 30.8 
Ridge Lake 6.48 Bennett et al. (1969) ia 138.0 9 45.1 
*Computed from years 1950, 1952, and 1953. 
ange was from only 1.16 to 1.27, with an average 
f 1.24. Thus it is clear that the uncaged fish made 
fficient use of the pond’s natural foods, and made 
ignificantly greater gains than the caged fish while 
eceiving proportionately smaller rations. For ex- 
mple, when the final census weights were used to 
ompute the percentages of total weight contained 
n the daily ration, the caged fish were receiving 
31 percent of their weight, while the heavier and 
aster-growing uncaged fish were receiving a daily 
ation equivalent to only 1.03 percent of their weight. 
DISCUSSION 
It is widely accepted that the elimination of pre- 
xisting pond fishes is a prerequisite to the successful 
roduction of channel catfish in commercial quantities. 
t is believed that the companion fishes will utilize 
od intended for the catfish, and might further 
sduce the potential for catfish production through 
ompetition for oxygen and space. While this might 
ery well be true for certain types of companion 
shes, such as bullheads (Ameiurus sp.), or one of 
le carps (Cyprinus sp.), it may not be true for 
thers. An earlier study (Buck et al. 1972) produced 
vidence that commercial quantities of both channel 
itfish and golden shiners can be raised in combined 
ilture, and results of the present study suggest that 
tannel catfish can be raised in commercial quantities 
| ponds containing established populations of bass 
id bluegills without detriment to either culture. 
ich a combination could retain the recreational 
pects of a pond through angling provided by the 
‘ss and bluegills, while the catfish could provide 
Iditional angling pleasure and food for the table 
Well as a cash crop. 
It should be recognized, however, that the com- 
ning of such species presents certain problems, and 
ould require certain precautions. A primary pre- 
ution would be to avoid overstocking and overfeed- 
§ to the point that accumulated organic wastes 
auld cause a depletion of the supply of oxygen. 
A second precaution would be the stocking of 
eder catfish of sufficient size to prevent excessive 
edation by the larger bass. In 1970 we suspected 
that poor survival of catfish in one pond may have 
been due to such predation. In this instance the 
catfish had an average total length of 5 inches (127 
millimeters) when stocked, and the bass population 
contained eight individuals sufficiently large to prey 
upon catfish of this size; however, survival of catfish 
was almost twice as high in the replicate pond where 
the potential for predation was similar. When re- 
stocked in 1971, the catfish had an average total 
length of between 9 and 9.5 inches (228.6 and 241.3 
millimeters), and predation was not a problem, al- 
though the bass were larger. The use of cages would, 
of course, permit use of smaller catfish and totally 
eliminate the predation problem. An additional pre- 
caution against predation would be to remove the 
larger bass at harvest time, along with excessive 
numbers of bluegills. Selected bass and bluegills 
might then be returned to the pond to preserve the 
angling population. While the sorting out of the bass 
and bluegills during the catfish harvest would con- 
stitute a considerable nuisance, it might be worth the 
effort. Additional cash income could well be realized 
through the sale of excessive bluegills and the larger 
bass since a ready market now exists for both species, 
in Illinois as well as elsewhere. 
Harvesting of catfish could be simplified by con- 
fining them to cages, but our study showed greater 
gains on a lesser amount of feed by catfish when 
they were free in the pond to supplement their ration 
with natural foods. Elimination of cages would also 
obviate the labor and cost of their construction, and 
lessen food costs. As shown in a companion study 
(Buck et al. 1973), caged catfish require a more 
complete and much more expensive feed because 
they have only a very limited access to natural foods. 
Further mention should also be made of the 
apparent interaction between the uncaged catfish 
and bluegills in 1971 wherein the smallest numbers 
but the greatest weights of Age 0 bluegills were 
found in those ponds containing uncaged catfish. The 
data suggested that the catfish production was im- 
proved through predation of the small bluegills, and 
that the population of bluegills was in turn improved 
through a beneficial thinning of their numbers by 
7 
