x S. hornorum hybrid grew the fastest (1.8 g/day) the S. mossambicus x S.
hornorum hybrid at 1.4 glday and the S. niloticus x S. aureus hybrid at
1.3 g/day. The results are preliminary as carp mortalities in several ponds
may have biased the data. Pruginin (1967) found no significant differences
between the growth of all-male hybrids S. niloticus x S. hornorum and S.
niloticus x S. aureus.
ProductionPruginin (1968), working with the all-male hybrid of S. niloticus x S.
hornorum in Uganda, reported yields of 800 kg/ha/year when 1,500 hybrids/
ha were stocked. When hybrids were stocked at 8,00O/ha the rate of growth
up to 50 g did not differ from that of fingerlings stocked at lower rates. After
reaching 50 g, hybrid fingerlings previously maintained at high densities were
then transferred to growing ponds at a density of 1,000 to 1,500lha. Under
these conditions, the individual weight gain of hybrids was 1.5 to 3.0 g/day to
reach 200 to 450 g after 100 to 150 days. It was not stated whether supple-
mentary feeds or fertilizers were used in these trials. Hickling (1962) reported
that all-male hybrids produced at Malacca, Malaysia, reached weights of
about 550 g in 6 months when stocked at 1,00O/ha, giving a total production
of 552 kg/ha/6 months from production ponds receiving 1,000 kglha of
limestone and 22.4 kg of triple superphosphate (TSP)/ha.
Pond experiments in Ivory coast by Lazard (1973) resulted in the produc-
tion of 1.396 kg/ha/year of all-male hybrids (S. niloticus x S. hornorum)
using TSP applied at the rate of 13.5 kg/ha every 2 weeks. The fish were
stock&&- 10,00O/ha at an average";jeight of 2 g and after 180 days reached
an average weight of 98 g.
Lovshin et al. (1977) also studied the growth and production of the
same all-male hybrid in 355-m2 earthen ponds in Brazil. Water entering the
ponds had a pH of 7.8 to 8.3 and total alkalinity of 140 to 150 mg/l. An
early experiment tested three treatments replicated three times each at two
levels of stocking, 5,600 and 8,960 fish/ha. The treatments were a control,
culture with cattle manure, and culture with supplemental feed (50% castor
bean meal and 50% wheat bran) fed at 3% of the fish biomass per day for
6 dayslweek. Ponds receiving cattle manure were fertilized once a week with
840 kglha. Hybrids were stocked at an average weight of 7 g to determine
growth during a 253day eriod. The average total productions for ponds
stocked at 5,600 4 a re 300, 804 and 980 kg/ha for the control ponds,
manured ponds, and fed ponds, respectively. The corresponding figures for
ponds stocked at 8,96O/ha were 277, 1,016 and 1,778 kg/ha. The fish grew
best in the fed ponds at 8,96O/ha: average individual weight, 229 g; feed
conversion ratio (FCR), 2.7. The differences in production between the two
levels of stocking and between treatments at each level of stocking were
significant (p < 0.05).
A second experiment was performed using different culture methods
(organic fertilizer, inorganic fertilizer and organic fertilizer plus feeding, all