hybrids are normally 30 to 50% of the total fish population and their yield is
20 to 30% of the total.
In Brazil, Lovshin et al. (1977) tested the culture of the S. niloticus
x S. hornorum all-male hybrid with mirror carp (Cyprinus carpio) to deter-
mine whether the addition of mirror carp would increase total fish produc-
tion. Mirror carp raised alone were stocked at 2,24O/ha, tilapia hybrids
in monoculture at 8,96O/ha and tilapia hybrids and mirror carp combined
at 8,96O/ha and 1,40O/ha, respectively. All ponds received applications
of cattle manure at 1,400 kg/ha/wk for 5 months after which applications
were suspended. Rice polishings were fed throughout the 245day culture
period at 3% of the body weight of fishlday, 6 days a week. At harvest the
average productions were: carp alone, 812 kg/ha; tilapia hybrids alone, 3,993
kg/ha and combined culture, 3,567 kg/ha. There were no significant differ-
ences in total production (P < 0.05) between treatments with the tilapia
hybrid alone and the combined hybridcarp cultures. However, these two
treatments both produced significantly more harvestable fish than with carp
alone. Moreover, the combined culture averaged 105 kg/pond of tilapia
hybrids and carp raised on 295 kg of feed, while 108 kg of tilapia hybrids
stocked alone required 441 kg of feed. Thus, less feed was required to raise
an equal weight of hybrids and carps than was needed to raise hybrids alone.
The average weight of tilapia hybrids raised with carp was 285 g, while that
of the hybrids cultured alone was 353 g.
Da Silva et al. (1978) studied the influence of the all-male tilapia (S.
niloticus x S. hornorum) in combined culture with tambaqui (Colossoma
macropomum) a hitsating characid native to the Amazon River. Six
355-m2 ponds were stocked with 25 g tambaqui at the rate of 5,0001ha.
Three of the ponds were stocked with an additional 5,000 all-male tilapia
hybrids per hectare, with an average weight of 18 g. The fish were fed daily
on a pelleted chicken ration (17% protein) at 3% of the average body weight
of tambaqui only in the afternoon, 6 days a week for 365 days. Feeding
rates were recalculated monthly based on seine samples. The monoculture of
tambaqui produced an average of 6,683 kg/ha with fish averaging 1.50 kg.
The FCR was 2.8. The combined culture produced an average of 5,640 kglha
of tambaqui averaging 1.20 kg and 3,299 kg/ha of tilapia hybrids averaging
0.75 kg. The FCR for the combined culture was 1.8. The addition of tilapia
hybrids increased fish production by a total of 2,256 kg/ha compared to
the monoculture of tambaqui without increasing the quantity of feed or the
worsening the FCR.
To further test the influence of the all-male tilapia hybrid on tambaqui
culture, Da Silva et al. (unpublished data) stocked the equivalent of 10,000
tambaqui per hectare together with 3,000, 4,000, and 5,000 all-rnale (S.
niloticus x S. hornorum) hybridslha in 355-m2 ponds. Each tilapia hybrid
stocking rate was replicated three times. The average initial weights of the
tambaqui and tiapia hybrids were 39 g and 13 g, respectively. The fish were
fed a pelleted chicken ration (17% protein) at 3% of the average body weight
of tambaqui in each treatmentlday, 6 days a week for 360 days. Feeding
rates were recalculated monthly based on seine samples.
The average tambaqui productions were 7,453, 7,201 and 7,779 kg/ha,
with average weights of 760, 785 and 770 g for the 3,000, 4,000, and
sean pound
(Sean Pound)
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