Breeding

Most farmers choose to keep only male tilapia in the grow out stage. Male tilapia have proved to be more profitable as they grow bigger and are more time and energy efficient. Female tilapia tend to waste energy and time due to breeding.

Due to the rivalry nature of male and female tilapia, most farmers try to keep only male tilapia in grow out. Various techniques are currently in use to try and produce only male tilapia offspring. A few of the genetic advances in this area are listed below.
Methyltestosterone technique (MT)

This method involves adding methyltestosterone to the juvenile diet. This effectively makes females develop as males whilst the males are left unchanged. No residue from the chemical is left in the fish at harvest as it disappears after 30 days, but this technique still faces ethical and safety issues. It has been reported that this method can cause a degree of liver damage to the fish.
To try and reduce the use of MT, other methods have been developed such as, the YY method.
YY Method

This technique produces YY chromosome males.

The first generation fry are treated with estrogen so that all XY females are produced. These are then mated with males that are known to be XY. This generation are then mated with XX females.

From this, it can then be determined which breeder fish are YY 'supermales' as they will only produce XY male offspring.

These fish can then be kept as YY breeding males.
Hatchery Systems

For best hatchery practice it is sensible to stock one male to three females. In order to prevent the females from incubating their eggs orally, the eggs should be removed. This allows for better control of hatching and allows for the female to produce the next batch of eggs.

Pond, or hapa, rearing can be used for large numbers whilst a spawning tank for smaller numbers.

Jar hatching has also been found to be a good way of hatching larger numbers with little supervision.

For creating the best health conditions and for having the most control, tray hatching can be a more affective method to use. However the drawback of this is that it is very labour intensive and therefore not the most cost effective technique.
Fish farming strategies that prevent overcrowding and stunting include:

1. Cage farming where eggs fall through the mesh to the pond bottom before the female can collect them for brooding
2. Polyculture with a predator fish, such as fingerling largemouth bass, at 400 per acre
3. Culture of only males (monosex). All-male culture is desirable in ponds not only to prevent overpopulation and stunting but also because males grow about twice as fast as females.

Methods of obtaining predominately male fish include:
1. Manually separating the sexes based on visual examination of the genital papilla of juvenile fish (hand-sexing)
2. Hybridising between two selected species that produce all-male offspring (for example, Nile or Mozambique females crossed with Blue or Zanzibar males)
3. Feeding a male hormone-treated feed to newly hatched fry for 3 to 4 weeks to produce reproductively functional males (sex reversal)
4. YY male technology (currently under development and not yet a commercial option).
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