chicken farm. The chicken manure was 79% organic matter. After 189 days,
an average of 1,350 kg/ha of fish were harvested, averaging 186 g. The FCR
for chicken manure to fish was 10. A summary of research results performed
on the all-male tilapia hybrid in northeast Brazil is found in Table 2.
Collis and Smitherman (1978) raised all-male S. niloticus x S. hornorum
hybrids in 400-m2 ponds in Auburn, Alabama. Fish averaging 29 g were
stocked at 10,00O/ha. Three ponds were each fertilized with the equivalent
of 28,381 kg/ha of fresh cattle manure (5,392 kg of dry matter) divided into
daily applications over a 103day culture period. Fish in three other ponds
were fed a commercial catfish diet (36% protein) at 3% of their body weight
per day. The average net productions in the manured and fed ponds were
1,646 and 2,663 kg/ha, respectively. The corresponding average fish weights
at harvest were 200 g and 318 g. The FCR's for manure and catfish diet on a
dry matter basis were 3.3 and 1.3.
Lovshin et al. (unpublished data) studied the effect of introducing S.
niloticus females and the resulting recruitment on the growth and production
of all-male S. niloticus x S. hornorum hybrids. Nine 350-m2 earthen ponds
were stocked with 10,000 all-male hybridslha averaging 11 g. Three ponds
were then stocked with an additional 2.5% female S. niloticus and 3 other
ponds with an additional 5% female S. niloticus. The female S. niloticus
averaged 16 g. The fish were fed agricultural by-products at 5% of the body
weight of the hybrids per day, 6 days a week over a 273day culture period.
Seine samples were taken monthly to determine the growth of the hybrids
&d recalculate feeding rates. The average weights of the hybrids from the
100% male, 2.5% female, and 5% female treatments were 481 g, 218 g, and
285 g, respectively. The corresponding average productions of all-male
hybrids were 4,286, 1,809 kg/ha and 2,186 kglha. S. niloticus recruits
increased the total fish production in the 2.5% female and 5% female treat-
ments to 4,309 and 5,451 kg/ha, respectively. The growth of all-male hybrids
was equal in the three treatments until the fifth month when the lom male
treatment showed a distinct advantage. It was possible to produce a 200-g
fish in 6 months in the all-male treatment, but 7 months were required in the
two treatments with females. While the 100% male treatment showed a
significant difference (P < 0.05) in hybrid growth and production compared
with the treatments containing females, harvestable hybrids were still ob-
tained in the treatments with tilapia recruitment.
Greenfield et al. (1977) demonstrated the profitability of raising all-male
hybrids using agricultural by-products as feeds in ~ortheast Brazil.
In Israel, Tal and Ziv (1978) state that the majority of S. niloticus x S.
aureus hybrids are raised in polyculture with common and silver carp.
The tilapia assume the role of a pond cleaner, maintaining the water in
good culture condition by consuming organic material and waste feeds that
would otherwise decompose and pollute the pond environment. In most
cases, the tilapia are able to increase total fish production without signi-
ficantly reducing growth or production of the other species. The tilapia