several systems by which earthen ponds can be manipulated to produce and
remove hybrid fingerlings and fry.
Lovshin (1980) describes a series of experiments performed in Brazil
to determine the best method for producing all-male tilapia hybrid fingerlings
by crossing S. niloticus x S. hornorum. One hundred and forty-two crosses
were made over a 6-year period in 360-m2 earthern ponds. A fingerling
production system for use in Brazil was developed from these experiments
and is detailed below (Figure 1). Plates 1-3 (see p. 308) illustrate some of the
facilities and species in use in Brazil.
Sarotherodon
hornorum
Step I
Pure Genetic
Id Strains
Sarotherodon
niloticus
I
Step n
I
Broodstock
Multiplication Ponds
males are sexed
at 20 to 30 grams
females are sexed
at 20 to 30 grams
Step IU
Male and Female
Preparation Ponds
\
Step ISZ
$s. hornorum
Q S. niloticus
Spawning Pond
Stocked at 60 to 100 grams
Figure 1. System used for producing all-male tilapia hybrids, S. niloticus x S. hornorum
in Northeast Brazil (after Lovshin 1980).