Table 6. Fry production (Sarotherodon niloticus? x S, aureus d hybrids) from 3 spawn-
ing ponds at Ein Hamifrats fish farm over the four month summer spawning season, har-
vested with a 5 mm mesh net.
Pond no.
Area (ha)
Parental stock
Females
Males
Removal of fry
End of July 650,000
End of August 230,000Total
No. of fry/? 628 749 656The Mass Production of Hybrid Tilapia FryFive or six million hybrid tilapia fry per year are now being cultured
commercially within the Israeli fish farming system, produced by a few
farmers who have acquired a lot of recent experience. However, only a part
of these produces pure-strain tilapias. It seems, therefore, that the future of
the Israeli tilapia culture industry lies in the hands of a few specialist hatch-
ery operators.
The problem of low fry production per spawner has been solved by
holding more parental stocks. Low productivity of spawners is, however,
only one of the problems that have an influence on the mass production
of fry. In countries with a warm temperate climate, like Israel, overwintering
of the fry is another problem. In Israel today, this has been recognized as a
serious limiting factor, and many farmers are experimenting with various
facilities which will help overcome it.
Tilapia fry under 20 grams are hardly able to survive the Israeli winter
temperatures. To overcome this problem, young fry must be introduced into
the nursing ponds early enough to reach or exceed this weight before the
winter. This takes about 60 days and the growing season ends at the beginning
of November. Therefore, the last date at which it is still worthwhile to start
nursing is September. This restricts the usable spawning period to four
months only: from May to the end of August.
In addition to these restrictions, the Israeli hybrid fry producers prefer to
harvest with nets of at least 5 mm mesh, because smaller mesh nets collect a
lot of mud and cause big fry losses. At the end of the spawning season,
therefore, hundreds of thousands of the small fry are left unharvested and
are not recorded as part of the total production of the spawning ponds.
During the four-month spawning period, not more than two or three spawns
can be expected from each female. Therefore a 400 g S. niloticus female
cannot produce more than about 2,500 fry per season. In practice, the best
yields obtained from females of this size in the Kibbutz Ein Hamifrats fish