Male tilapia have a higher growth rate than females, so farmers prefer raising male-only populations. There are four main methods to produce monosex tilapia populations: 1) Hybridization, which can result in predominantly male offspring; 2) Manual sexing; 3) Hormone treatment using androgens or estrogens; 4) Genetic manipulation including marker-assisted selection, cross-breeding, and transgenic technologies. Hormone treatments and genetic hybrids are common commercial methods that allow effective production of monosex male tilapia.

1. Monosex and Hybrid production in Tilapia
ANJUSHA. K. V
U-18-TN-03-002-D-F-001
DEPARTMENT OF AQUACULTURE
FC & RI, THOOTHUKUDI

2. Why Monosex Tilapia ?
• Tilapia farmers choose to raise male tilapia only since they have a higher
growth rate compared to females
• Male- batches can be obtained through three main methods:
1. Hybridization
2. Manual sexing
3. Hormones
4. Genetic manipulation
(It is difficult but not impossible)

3. Mono sex Tilapia through Hybridization
• It is the act of breeding between two different species/genera, which
ordinarily are not interbreeding.
• Examples:
Nile Tilapia × Blue Tilapia ( O. niloticus × O. aureus)
• Superior growth of males
• Fertile hybrids
• Increased cold and salinity tolerance
• Reciprocal cross gives 50% males & females

4. O. niloticus × O.
hornorum• Predominantly male offspring
O. niloticus × O. macrochir
• Predominantly male offspring, but strain of Nile tilapia is important for
good fry production.
O. Mossambicus × O. hornorum
• Predominantly male offspring
• Fertile hybrids
• Slow growth and dark colour

5. O. hornorum × O. mossambicus
• Red Tilapia with salinity tolerance
O. mossambicus × O. niloticus
• Red Tilapia with salinity tolerance
• Progeny of these give range of colours
• Known as Taiwan red tilapia

6. Production of Red Tilapia
• Red hybrid tilapia - popularity among culturists
due to their resemblance to premium marine
species such as sea bream & red snapper.
• Red tilapia are genetic mutants selected from tilapia species in the genus
Oreochromis.
• Oreochromis sp. are taxonomically distinct from other tilapia genera because
females incubate fertilized eggs in their mouths.

7. • The first reported red tilapia hybrid was produced in Taiwan in the late 1960s
• Cross between a mutant reddish-orange female O. mossambicus and a normal
male O. niloticus and is called the Taiwanese red tilapia
(Galman and Avtalion, 1983).
• Off-spring from red tilapia parents will contain fingerlings with wild or dark
coloration and red or pink coloration with irregular black spots.
• Red tilapia brood stock must be continually selected for red color .

8. Mono sex tilapia through hormone treatment
• Direct approach : monosex population produced directly by hormone treatment
• Indirect approach : monosex population can be obtained in two steps.
1. A broodstock population is established by sex reversal.
2. Then these sex reversed individuals should be bred to produce
monosex population.

9. Methods of Hormone treatment
 Dietary supplementation: The hormone mixed feed is the most widely
used and the easiest method for achieving sex reversal.
 Immersion technique: juvenile fishes are immersed in hormone
treated water.
 Injection : Injection requires less amount of hormone to cause sex
reversal. It is very much laborious and expensive.

10. Steroid Hormones
• Androgens: 17-α- methyl testosterone
Testosterone
11-keto testosterone
• Estrogens: Estradiol-17-β
Estrone

12. • Doses of 17α-MT - 40, 60 and 80 mg of 17 α - MT/kg of feed
(From the 7th to the 28th day posthatching to produce all male tilapia population)
• After 15, 35 and 75 days and 1 year of treatment - growth parameters,
survival rate, sex ratio and gonad histology
• The maximum sex ratios of males (95% and 97%) were recorded at 60
mg of 17 α -MT/kg of diet after 75 days and one year of treatment

13. Mono sex tilapia through Genetic manipulation
• Genetic manipulations - divided into three categories
1. Marker‐assisted selection(MAS)
2. Cross‐breeding
3. Genetic modification.

14. Marker‐assisted Selection
• Most efficient applications of biotechnology
• It improves selection efficiency compared to traditional selection schemes
• Selection is based on a marker linked to a trait of interest
(rothschild and ruvinsky, 2007) rather than on the trait itself.

16. Cross-breeding
• Cross-breeding (Hybridization) is an essential technique for natural
recombination of male and female genetic material from different strains
or different species.
• Hybrid tilapia - O. niloticus (♀) and O. aureus (♂).
• These hybrid tilapia are popular, not only because they grow rapidly (20
and 70% higher body weight than its female and male parent, respectively)

17. Genetic modification.
Transgenic Technology
• Transgenic technology is the introduction of exogenous genes into a recipient
organism, with the intention of changing the phenotype.
• gsdf transgenic XX tilapia showed normal testis development
(Kaneko et al., 2015).
• Crossing gsdf and amhy transgenic male with normal XX female may be an
effective method for producing all-male populations.

18. References:
• Marengoni, N. G., Onoue, Y., & Oyama, T. (1998). All‐male tilapia hybrids of two strains
of Oreochromis niloticus. Journal of the World Aquaculture Society, 29(1), 108-113.
• Hashim, R., Chong, A. S., Fatan, N. A., Layman, N., & Ali, A. (2002). Production of hybrid
red tilapia, Oreochromis mossambicus× O. niloticus, at varying stocking densities in
portable canvas tanks. Journal of Applied Aquaculture, 12(3), 1-12.
• TILAPIAAQUACULTURE 2016 AND WHERE WILL WE BE IN 2026. Kevin
Fitzsimmons,2016.
• The History, Status, and Future Prospects of Monosex Tilapia Culture in Thailand | The Fish
Site
• Applied fish genetics : B.K.Padhi and R.K.Mandal.
• A text of fishery science and Indian Fisheries :C.B.L.Srivastava
• Pinto, L. G. (1982). Hybridization between species of tilapia. Transactions of the American
Fisheries Society, 111(4), 481-484.