The Biology and Culture of Tilapias

'I ponds stocked with 8,960 fishlha averaging 21 g over 356days. Ponds in one
treatment received 1,400 kglhalweek of cattle manure, while ponds in a
second treatment were given TSP and (AS), each at a rate
of 29 kg/ha every 2 weeks. Ponds in the third treatment were fertilized with
1,400 kglhalweek of cattle manure and also re~eived-~~i~~of 50% c~&!
=-meal and 50% wheat bran fed at 3% of '6he fish biomass per day, 6 days
a week. All treatments were replicated twice. The average total fish produc-
tions were: organic fertilizer, 1,341 kglha; inorganic fertilizer, 1,856 kg/ha,
and organic fertilizer plus supplemental feed, 4,883 kg/ha. The corresponding
average final weights of fish were 154 g, 215 g and 565 g. Total production
with feeding plus fertilizer exceeded that with inorganic and organic fertili-
zer by 163% and 264%, respectively. These differences were significant
(p < 0.05).
Augusto and Melo (cited in Lovshin 1980) tested the effects of AS (20%
..-" Nj, TSP (46% P205), AS + TSP and no fertilizer (control on thc@i
of all-male hybnds (S. niloticus x S. hornorurn) .in 355-m^2 ponds for 190
days. The AS and TSP treatments were replicated three times while the
AS + TSP treatment and the control were replicated twice. Ponds in the
AS and TSP treatments received equal amounts of N and P O5 (280 g per
application). Ponds in the AS + TSP treatment received hdf this amount
(140 g per application) so that the total amount of N plus P20 applied was
equivalent to 280 g. Ponds fertilized with AS or TSP received 4.42 kglpond
application (40 - kglha) L_--- and 0.61 kglpond application (17 kglha), respectively.
Ponds receiving both fertilizers had 0.76 kgjpond application of AS (20
kg/ha) and 0.31 kglpond application of TSP (8.7 kglha). Ponds were fertilized
every 15 days by placing the fertilizer on a platform located 20 cm below
the water surface. All fertilized ponds received an initial application of
fertilizer 15 days before fish were stocked. Ponds were stocked with fish
averaging 20 g at 10,00O/ha. The average productions of the control, TSP,
AS + TSP and AS treatments were 350, 832,977 and 1,016 kglha, respec-
tively. Fertilizers increased the total production two to three times that of
the control. TSP alone was not as effective as AS alone or the combined
treatment.
Paiva et al. (cited in Lovshin 1980) tested the growth of the same all-male
hybrid fed three types of agricultural by-products found in .northeast Brazil.
Nine 355-m2 earthen ponds were stocked with 400 fish (i.e., 11,25O/ha),
average weight 15 g. Castor bean meal (30% protein), babacu cake (a palm
nut with 21% protein), and cottonseed cake 1(21.5% protein) were fed daily
at 3% of the average biomass of fish in each treatment 6 days a week. Feeding
rates were recalculated monthly based on seine samples. Treatments were
replicated three times in a random block design. The culture period was 238
days. The average total fish productions for castor bean meal, babacu cake,
and cottonseed cake were 3,444,2,605, and 2,264 kglha, respectively. These
differences were significant (p < 0.05). Fish fed castor bean meal were
heavier at harvest (323 g) than fish fed babacu (245 g) or cottonseed cake
(239 g), but there was no significant difference between fish fed babacu and
cottonseed cake. FCR's for castor bean meal, babacu cake, and cottonseed
cake were 2.4,2.6, and 2.7, respectively.