Induced breeding is a technique whereby ripe fish breeders are stimulated by pituitary hormone or any other synthetic hormone introduction to breed in captive condition. The stimulation promotes timely release of sperms and eggs.

1. Induced Breeding:
Induced breeding is a technique whereby ripe fish breeders are stimulated by pituitary hormone
or any other synthetic hormone introduction to breed in captive condition. The stimulation
promotes timely release of sperms and eggs.
Why induced breeding is necessary?
1. It gives pure spawn of certain species of fishes under cultivation. Spawn collected from
natural water is not pure as because some undesirable wild species may come with them in
culture pond. Sorting of pure seed is quite impossible in those stages. In later stages it is
possible, but time consuming.
2. It assures timely available of pure seed, where as in nature the availability of seed is quite
uncertain.
3. It can fulfil any quantity of demand in any time.
Tilapia are asynchronous breeders. Hormones are not used to induce spawning, which occurs
throughout the year in the tropics and during the warm season in the subtropics. Breeding is
conducted in ponds, tanks or hapas. The stocking ratio for females to males is 1-4:1 with 2 or
3:1 being the most common. The brood fish stocking rate is variable, ranging from 0.3-0.7
kg/m2 in small tanks to 0.2 - 0.3 kg/m2 in ponds. The popular hapa-in-pond spawning systemin
Southeast Asia uses 100 g brood fish stocked at 0.7 kg/m2. Spawning ponds are generally 2000
m2 or smaller. In Southeast Asia, a common hapa size is 120 m2.
Brood fish are given high quality feed at 0.5-2 percent of body weight daily. Swim-up fry gather
at the edge of a tank or pond and can be collected with fine-mesh nets. Fry collection can begin
10 to 15 days after stocking.
Multiple harvests (six times per day at 5 day intervals) are conducted up to a maximum of 8-10
weeks before pond drainage and a complete harvest is necessary. Tanks must be drained and
recycled every 1-2 months because escaped fry are very predaceous on fry from subsequent
spawns.
Production System

2. Commercial tilapiaproductiongenerallyrequiresthe use of male monosex populations.Male tilapia
grow approximatelytwiceasfast as females.Therefore,mixed-sex populationsdevelopalarge size
disparityamongharvestedfish,whichaffectsmarketability.Moreover,the presence of femaletilapia
leadstouncontrolledreproduction,excessive recruitmentof fingerlings,competitionforfood,and
stuntingof the original stock,whichmaynotreach marketable size.Inmixed-sexedpopulations,the
weightof recruitsmayconstitute upto 70 percentof the total harvestweight.Itistherefore necessary
to reverse the sex of female fry.Thisispossible because tilapiadobecome sexuallydifferentiatedfor
several daysafteryolksacabsorption.If female tilapiareceive amale sex hormone (17α
methyltestosterone,MT) intheirfeed,theywilldevelopasphenotypicmales.
Breeding mono-sex tilapia
Many of the most commonly farmed tilapia species breed easily and rapidly even in farm
conditions. This means that if a farmer keeps male and female tilapias together, it will be hard
to control breeding rate, quantity and quality. Soon, the growing units will be filled with fry of
low economic value. The adult fish will also spend energy breeding instead of growing. It is
therefore easy to understand why so many farmers prefer to raise only one sex. Most farmers
choose to raise male tilapia only, since male tilapias grow bigger than the females. This has
placed a demand on the fish breeding industry to produce mono-sex tilapia, i.e. males only
groups that can be sold to farmers.
Oreochromis niloticus Linnaeus, 1758 [Cichlidae]
Sex-reversal

3. Breeding mono-sex tilapia by using hormones
If newly hatched tilapia fry are subjected to sufficient amounts of male hormones, they will
turn into reproductively functional males. This method is also known as the sex reversal-
method. It is normally carried out by feeding newly hatched tilapia fry with special hormone
treated food for 3-4 weeks. The size of tilapia fry is normally determined 2-6 weeks after
hatching. It is important to keep in mind that the use of hormones is restricted in many parts of
the world. You might for instance require a special license to produce hormone-food and/or
feed it to your tilapia.
Production cycle of Oreochromis niloticus
Breeding mono-sex tilapia through hybridization
When certain species of tilapia mate, the offspring will be all-male. This will for instance occur
when Blue tilapia (Oreochromis aurea) or Zanzibar tilapia (Oreochromis hornorum) males mate
with Nile tilapia (Oreochromis nilotica) or Mozambique tilapia (Oreochromis mossambicus)

4. females. In Singapore, the problem with invasive tilapia in the form of Oreochromis
mossambicus might actually be on its way of resolving due to the introduction of other exotic
tilapia species and hybrids, since the sex ratio of the resulting hybrids are so strongly skewed in
favour of males.
The genetics of tilapia hybrids is complicated and many crosses will not produce 100 percent
males. Oreochromis aurea females that mated with Oreochromis nilotica males in a study in
Israel did for instance produce 80-90 percent males, while Mexican try-out where Oreochromis
nilotica females were bred with Oreochromis mossambicus males produced no more than 80
percent males.
Breeding mono-sex tilapia by using YY male technology
YY male technology for tilapia breeding is still under development and is not yet a commercially
available alternative.
Conclusion:
Tilapia are mainly freshwater fish, inhabiting shallow streams, ponds, rivers and lakes, and less
commonly found living in brackish water. Historically, they have been of major importance in
artisan fishing in Africa and the Levant, and are of increasing importance in aquaculture and
aquaponics.
Refference
http://monjit-paul.livejournal.com/4100.html
http://www.aquaticcommunity.com/tilapia/breeding-monosex.php
http://www.fao.org/fishery/culturedspecies/Oreochromis_niloticus/en
http://pdacrsp.oregonstate.edu/pubs/workplns/wp_9/9rcr7.html