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With tilapia, the use of mono-sex populations is essential for the profitability of the industry, in the light of the reproductive characteristics of the species which, in ponds, leads to overpopulation and dwarfism among the individuals. These mono-sex populations encourage the best growth of the males at the end of the production period, a male being 1.6 times larger than a female on average. Considering the size of the industry (2.8 million tons, over 100 producer countries, the world's second largest piscicultural), any improvement in controlling sex leads to important economic benefits.
These mono-sex populations are generally produced by hormonal inversion. In a context of ecological intensification, research in alternative hormone-free processes which are acceptable both for the consumer and the environment, is a challenge for aquaculture. In the short and medium term, the alternatives rely on genetic or environmental (thermal) approaches.
Without early sexing, the fish farmer rears all product batches without knowing their initial sex -ratio and therefore their growth potential. Whichever sex control method is used on tilapia, early sexing will very greatly improve efficiency and profitability. The 'UR Aquaculture du Cirad' has acquired an international reputation in the field of tilapia sex determination/differentiation, as well as in alternative research approaches. The group recently cloned the Male gene which allows any individual of the male phenotype to be identified as early as 14 days old. The SEXTIL project (Sexing of Tilapia) proposes to:
1) put together a diagnostic kit based on the expression of the Male gene, for tilapia early sexing laboratories,
2) develop a sexing kit which is easier to use and which relies on the protein coded by the Male gene for medium-sized and large production companies,
3) validate these 2 types of kit on most domestic strains of Nile tilapia (Bouaké, Manzala, GIFT ..), and on other species of farmed tilapia (blue tilapia, Mozambique tilapia, strains of red tilapia),
4) carry out a market study to analyse the potential of these sexing kits on the three main continents (Africa, Asia, Latin America) for the production of tilapia, and allow a French company (start-up) to market these kits on a global scale.

These kits will allow producers to improve the profitability of their farming through the early elimination of batches containing low proportions of males and the quality and durability of their production and companies by facilitating the selection of genotypes of interest.
These kits will also facilitate research, in laboratories/stations, on sex determination and differentiation, and the development of genetic and/or thermal approaches for a sex control that respects both the consumer and the environment.

This project was labelised by the AQUIMER Pole of Competitiveness on the 13th July, 2010.


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