The Biology and Culture of Tilapias

resuits are also poor: the soya pellets did not improve on results obtained

with fresh algal feeds (see F2 above) and animal protein pellets gave only

slightly better results. This suggests that S. mossambicus and T. guineensis

have low potential for cage culture.

In Indonesia, 10 to 25% S. niloticus are cultured with Cyprinus carpio
in cages in a 20 ha lake at the Lido Station (Pedini ers. comm.). The cages
are relatively large (9 m2 x 1.25 m deep and 81 m x B 1.25 m deep) and a
pelleted feed (32% protein) is given to the carps only at DFR 3% carp
biomass. S. niloticus is here considered as a secondary crop. In Taiwan also
an experimental cage (144 m3) was stocked with tilapia (probably S. niloticus
x S. mossambicus hybrids) and C. carpio (see Table 14). The growth of the
tilapias was very good, even though far below that of common carp. The
carp were so infested with parasites, however, that the local farmers now
prefer tilapias for cage culture, even though their growth is slower and pro-
duction smaller (de la Cruz 1979).

In the Ivory Coast S. niloticus is being culturkd in cages placed in coastal

lagoons where the salinity may reach 20%. Some experiments are in progress,

but until now results have been rather disappointing, the average growth rate

varying from 0.20 to 1.17 g/day on a 15.5% protein feed (De Kimpe 1978).

However, British Petroleum has established a commercial farm for intensive

tilapia cage culture in Jacqueville (about 64 km west of Abidjan), including a

hatchery/nursery and a feed mill. Both S. niloticus and S. melanotheron (T.

heudelotii) are being tried in commercial size cages (27 and 54 m3). The

production potential of the farm is estimated at about 500 tiyear (Campbell

pers. comm.) but only preliminary data are available. Although S. niloticus

has demonstrated an excellent growth rate (1.8 to 2.1 g/day), great mortalities

have been experienced due to heavy parasitism. S. melanotheron (T. heude-

lotii), a species endemic in the local lagoons, has also been tried with very

little mortality but its real potential for cage culture has not yet been estab-

lished.

Advantages, Constraints and Research Needs

When compared with the more traditional methods of fish culture in

ponds and tanks, cage culture presents some definite advantages (Coche

1978, 1979). In the particular case of tilapias, the major advantage is the

possibility of controlling unwanted recruitment (Pagh 1975).