Taste 2.—Means of final standing crops for channel catfish (CC), golden shiners (GS), tilapia (T), and all species combined (All), i 
10-foot-diameter plastic pools, compared with ranges and seasonal averages of pH, and of parts per million of turbidity, ammonia, car 
bon dioxide, and total alkalinity. The pools were maintained outdoors over an 84-day growing period, with two replications for each typ 
of population. 
Final Weight (Ibs/A) 
Range (in parens) and Seasonal Average 
Type of CC GS a All pH 
<= 
* 4384 . 438 (7.2-10.0) 
b 81 
eG : 884 4 3814 & 1,265 (7.5-10.0) 
8.3 
Woe 447 588 2,047 (7.4-10.0) 
8.2 
iid iit (7.4-10.1) 
8.2 
1,011 1,011 (7.5-10.1) 
8.3 
tt 258 ue 258 (7.8-9.9) 
8.3 
# 226 2 226 (7.3-9.4) 
8.3 
560 294 “t 854 (7.4-10.0) 
8.2 
460 171 . 631 (5.7-9.5) 
8.4 
637 237 338 owe (7.4-9.9) 
1) 
4 Populations contain shiners in lots of 45 or 90, catfish in lots of 8 or 16, 
and tilapia in lots of 5 or 10. 
b Designates pool containing 16 catfish and 90 shiners intermixed. 
shiners, or the amount of food received by the pool. For 
example, turbidities were consistently higher in those pools 
having only catfish, but where the catfish had access to all 
of the pool bottom, than in a) the pools where the same 
numbers of fish received the same amount of food but were 
restricted to one-half the pool, or in b) those pools where 
the same number of catfish were restricted to one-half the 
pool but where food received was greater due to the pres- 
ence of 90 shiners in the other half. In these instances, tur- 
bidities were due primarily to densities of phytoplankton, 
and these greater densities were believed related to the in- 
teraction of the catfish with the bottom mud. Stirring of the 
bottom by catfish did not muddy the water but it was prob- 
ably sufficient to increase the release of soil nutrients into 
the water for use by phytoplankton. The shiners therefore 
appeared to gain an indirect benefit from their association 
with catfish due to the greater production of phytoplankton 
associated with the catfish. 
Also of interest were the differences in food conversion 
Turbid- NHs CO2 Alkal- 
ity (ppm) (ppm) inity 
(ppm) (ppm) 
(8-220) (0.04-.97) (0-18.1) (56-123) 
76 0.41 bee. 80.0 
(7-106) (0.01-.72) (0-9.5) (57-100) 
46 0.31 2 70.5 
(G=2.95) (0.04-1.61) (0-13.3) (52-113) 
85 0.44 3.9 TSet 
(5-210) (0.00-.96) (0-9.3) (57-99) 
60 0.33 3.4 71.4 
(2-92) (0.00-.60) (0-10.4) (59-98) 
34 0.27 ah.8 72.9 
(0-32) (0.00-.46) (0-12.4) (55-85) 
16 0.19 ou 67.7 
(0-19) (0.00-.47) (0-6.9) (57-84) 
8 (Chily 25 66.8 
(7-150) (0.00.83) (0-10.8) (57-115) 
55 0.34 3.8 74.8 
(4-60) (0.04-.60) (0-6.9) (57-97) 
27 0.23 2.2 67.0 
(1-196) (0.00—.80) (0-13.3) (57-110) 
65 0.50 3.5 72.0 
© Designates pool containing 16 catfish separated from 90 shiners by a net. 
d Data from one pool only due to excessive mortalities in its replicate. 
ratios and their relationship to turbidity. Conversions We 
computed on the somewhat vulnerable assumption th 
each species ate only its assigned ration—pellets for the 
fish and tilapia, and meal for the shiners. While the 
sumption cannot be completely true, the data are nonetl 
less informative. 
Table 3 presents all conversion statistics for which di 
are available. At the higher density levels the most efficic 
conversion ratios by catfish occurred in those pools conta 
ing only catfish and having intermediate (34-60 ppm) tt 
bidities (Table 2), whereas the least efficient conversions 
shiners were in those pools containing only shiners a 
having very light turbidities (8-16 ppm). 
In those pools containing both catfish and shiners, ¢ 
versions by catfish were slightly, but not significantly, lo 
er when mixed with shiners than when separated fr 
them by a net, whereas conversions by shiners were Sigh 
cantly lower (1) when mixed with catfish than when sep 
ated from them by a net, (2) when separated by a net | 
1 
