Development of two precocious sexing tests for tilapia to be used by farmers and research laboratories – SexTil

The main objective of the project will be to convert the knowledge on the Male M-gene into a practical, diagnostic and commercial sexing procedure for tilapia, to be used by both scientists and farmers. The development of a molecular fish-sexing kit has never yet been proposed for fish. Two types of sexing-kits will be developed so that they can be used by both professions. The tasks of this project are:
1) Construct an easy sexing kit for Nile tilapia to be used in laboratories by analysing precociously the expression of a Male-gene.
2) Develop an easier sexing kit to be used by tilapia farmers consisting on the protein coding the Male-gene. 3) Validate these 2 types of kits on important Nile tilapia strains (Bouake; Manzala; GIFT..) and on the other farmed tilapia species.
4) Perform a marketing exploration study to analyse the potential of these sexing kits worldwide, and thus help a French company (for instance a Start-up) to commercialize the kits worldwide.

The M-gene was proven to be able to sex larvae, detecting genetic XY males. But we also showed that the M-gene allows the sexing of masculinised or sex-inversed individuals distinguishing them from females. The test worked on several masculinising individuals such as androgen-treated fish and temperature-treated fish. In addition, it is also valid at later stages and therefore, it widens the precocious sexing period. These results increase the value of the sexing kit, because it considerably enlarges the global markets since the majority of tilapia farmers use androgens to produce male fish.
A global marketing study was performed to analyse the potential of the sexing kits in the three major continents (Asia, Africa and Latin America) of tilapia production. Descriptive brochures were created in English, Spanish and Portuguese, and were sent with a survey to several forums and producers lists. The survey allows us to know what sex controlling method is currently used for each farmer, what it costs and to explain the interest and advantages of a precocious sexing in tilapia by the Sextil kit.
For the moment most (97%) of the tilapia producing companies who have answered the survey have shown an interest in the precocious sexing kit if it is sold at an adequate price for the number of sexing that they need to do annually. The economic gain that the farmers would have by using the sexing kit is being evaluated and will allow establishing the optimal price for the farming kit. The search for French companies (Start-ups) which could potentially commercialise the kits at a global scale will be performed shortly. In addition, to optimize quality standards, we are in the process of obtaining the “Label Fiabilité Mesures” that follow the requirements for ISO17025.

Validation of the sexing procedure is currently being performed on several different tilapia strains (Bouaké, Manzala, Philippines, Kenya ..) as well as in other tilapia species. Contacts have been made with several tilapia producers of variable sizes and an economic feasibility plan was carried out to estimate at what prize the sexing kit would interest farmers. We consider that more farmers need to enter this plan for a good estimation/continent. Farmers will be interested since they can eliminate unwanted batches much earlier increasing their benefits.

- A publication entitled «A precocious molecular procedure for sexing tilapia » will be submitted.
- Two orals communications have been given to the tilapia scientific community and producers that have attended (more than 250) the International Symposium of Tilapia Aquaculture (ISTA10), Jerusalem, Oct., 2013. 1) “A precocious molecular procedure for sexing tilapia”, by H. D’Cotta; 2) “Sex control in tilapia” by JF. Baroiller.
- Descriptive brochures in French, English, Spanish and Portuguese on the sexing kit for Farmers
- Survey in these different languages on sex control and the interest of the early sexing kit.

In tilapia, all-male populations are beneficial for farmers because males have a faster growth-rate than females and it avoids the constraints associated with reproduction. Considering that a male grows 1.6-fold more than a female after 7 months of culture and that tilapia annual production is 2.8 million tons (2nd World Fish production), there is a substantial economical gain for producers. All-males are commonly produced by androgen treatment to masculinise XX larvae. Search for alternatives based on more consumer and environment-friendly methods represents a major challenge for aquaculture. Both genetic or temperature sex control are good alternatives but require long progeny testings to sex & identify fish. Furthermore, selection of breeders (YY males & XX female) giving 95-100% males is necessary. A reliable and precocious sexing procedure would accelerate progeny testings, finding of particular genotypes and reduce production costs for farmers. It will also help scientists in developing temperature and genetic approaches for sex control. The Cirad-INTREPID Unit proposes in the SexTil (Sexing Tilapia) project to: 1) Construct an easy sexing kit for Nile tilapia to be used in laboratories by analysing precociously the expression of a Male-gene. 2) Develop a simpler sexing kit to be used by tilapia farmers consisting on the protein coding the Male-gene. 3) Validate these 2 types of kits on important Nile tilapia strains (Bouake; Manzala; GIFT ..) and on the other farmed tilapia species. 4) Perform a marketing exploration study to analyse the potential of these sexing kits worldwide, and thus help a French company (ie start-up) to commercialize the kits worldwide. Thus it will have considerable economical repercussions, reducing feeding costs, the necessary rearing space, labour and time requirements as well as promote environmentally-friendly sex control alternatives to hormones.