Taste 3.—Mean conversion ratios of artificial feeds by catfish, 
hiners, and tilapia, each species individually and the species 
ombined, over two time intervals and under different types of 
ssociation and confinement for two replications of each type 
opulation. Species are designated as: CC = channel catfish, GS 
= golden shiners, T = tilapia. All indicates a combination of all 
pecies. The populations were maintained outdoors in 10-foot 
iameter plastic pools. 
7/16/68-8/13/68 7/16/68-9/11/68 
1/16/68-8/13/68 ie rea 88 Ns 
tipn? foe CS mAll COMIGS MG Tan. Ali 
a STA 
16 4 1.55 088 1.31 
16 \‘ See le S85 1676 
00 
6 
10) 198 1.03 065 1.99 
0 
6) 1.44 1.78 
6 
®) 1.51 1.65 
0) 259 
0 
3.02 
1.094 0.624 0.944 
3 2.09 237 214 
) 1.50 1.05 0.53 1.7 
opulations contai 
lots of 5 or 10, 
esignates pool containing 16 catfish and 90 shiners intermixed. 
esignates pool containing 16 catfish separated from 90 shiners by a net. 
ita from one pool only due to excessive mortalities in its replicate. 
ing the same water than when in 
n mixed with catfish than when in 
should be noted, however, that t 
inkton were also consistently 
€s were in direct association an 
S to the entire bottoms of the p 
igher turbidities favored bo 
Ts probably gained a part of t 
plankton which caused the hi 
n shiners in lots of 45 or 90, catfish in lots of 8 or 16, and tila- 
a pool alone, and (3) 
a pool alone. 
urbidities due to phy- 
highest where the two 
d where the catfish had 
ools. This suggests that 
th species and that the 
heir sustenance from the 
gher turbidities. 
id Series 
thods.— A second series 
1ed as a homo 
fish productio 
1 if the prese 
of outdoor experiments was 
geneity study to measure the variations 
n within and between pools and to de- 
nce of the divider screen and the conse- 
confinement of the fish to a smaller area (while main- 
g the same density) had in itself any measurable in- 
© upon production. It involved only fed catfish in 
DOOls. Each pool was stocked with 16 catfish (8,880 
re), but four pools were divided into equal halves by 
netting, and equal numbers (8) were placed on each 
‘the dividing screen. The catfish were from the same 
d of the same size as those stocked in the outdoor 
reviously discussed and were fed at the same rate. 
of the catfish and shiners in th 
may be inferred partly by direct, 
e 
However, only three divided 
produced useful data because o 
population and the intermixin 
in a second pool. 
Results.—There was no m 
Provided usable data, and th 
from 927 to 1,110 
and three undivided pools 
f excessive mortalities in one 
g of the divided populations 
ortality in the six pools which 
€ final standing crops ranged 
pounds per acre, with a mean of 1,026. 
There was no significant difference (.05 level) in the pounds 
of catfish produced in the six pools, indicating that the exis- 
tence of the dividers and the confinement of the catfish to 
half the pool area had no influence on catfish production. 
The average final standing crop in these six pools, 1,026 
pounds per acre, was very similar to that of 1,061 obtained 
concurrently in the four pools in our other series which con- 
tained catfish only. 
DISCUSSION OF 1968 EXPERIMENTS 
Results from the indoor experiments differed from those 
obtained in outdoor pools because of the great differences in 
the experimental environments. The indoor pools con- 
tained no soil substrates, foods eaten were entirely artifi- 
cial, and the water was maintained at a constant tempera- 
ture of 72-75° F., which is below that considered opti- 
mum for growth of either catfish or shiners. The outdoor 
pools contained a soil substrate which, when ‘“‘worked”’ by 
catfish, contributed to the dense blooms of phytoplankton, 
which in turn contributed to the diet of both shiners and ti- 
lapia. Additional foods for the outdoor fishes included ter- 
restrial insects which at times entered the pools in substan- 
tial numbers, as well as a large complement of aquatic in- 
sects, including mayflies, dragonflies, anda variety of 
midges, which very quickly colonized the outdoor pools and 
began reproducing. There were also substantial differences 
in fish densities in the indoor and outdoor populations. 
Final standing crops of shiners in the indoor pools great- 
ly exceeded those produced outdoors, while the outdoor 
production of channel catfish greatly exceeded that pro- 
duced indoors. Greater production of shiners indoors was 
due in part to the greater density per pool (400 vs. 90) and 
to the longer growing period; but greater weights of chan- 
nel catfish were produced outdoors in spite of a much lesser 
density (16 vs. 100) and a shorter growing period. Factors 
contributing to the greater production by catfish outdoors 
probably included higher water temperatures and the avail- 
ability of natural foods. 
The presence of shiners and tilapia caused little or no 
ss of catfish production in the outdoor pools. 
duction by catfish indoors suggests that growth 
been inhibited by the high density of shiners, alt 
water temperatures were also important. 
The much greater production of shiners indoors indicat- 
ed that growth was inhibited very little by the combination 
with a dense population of catfish, by the relatively low 
water temperatures, or by the higher levels of ammonia and 
carbon dioxide in the indoor pools. 
The degree of behavioral and physiological compatibility 
e densities here employed 
but largely by indirect, 
hat no antagonistic be- 
lo Poor pro- 
may have 
hough low 
vidence. We pointed out earlier t 
