Tilapias tend to be prolific fishes and their fry often have a high survival rate. This means that if you raise tilapia in a pond and allow them to reproduce freely, the pond will soon be filled with various size of tilapia – all competing with each other for food and space. This is not beneficial for any of them and will usually lead to decreased growth rates and stunted specimens.
In the wild the problem would normally be solved by predators filling their bellies with tilapia but farming ponds are often devoid of predators. One alternative is of course to introduce predators of a suitable size that will feast on juveniles while leaving the precious adult fish alone. Another solution is not to keep males and females together, i.e. to raise mono-sex tilapia.
When a farmer has to choose between male and female tilapia the most common choice is male tilapia since males grow faster and bigger than females. Male-only batches can be obtained through three main methods: hybridization, manual sexing, or hormones.
Mono-sex tilapia through hybridization
When certain tilapia species or strains mate with each other virtually all of their fry become male. When females do occur they are usually the result of foreign genetic material being present in one or both parent fishes due to earlier hybridization. If you need an all-male batch for your fish farm you can for instance contact a breeder that mates female Nile tilapia (Oreochromis nilotica) with male Blue tilapias (O. aurea) or male Zanzibar tilapias (O. hornorum). Crossing males of the species O. aurea or O. hornorum with females of the species O. mossambicus (Mozambique tilapia) is another popular alternative.
Mono-sex tilapia through manual sexing
Manually sexing tilapia is difficult but not impossible. It is however very labour-intensive and therefore costly.
Mono-sex tilapia through hormone treatment
By subjecting young female tilapias to hormones, it is possible to turn them into males. Before you opt for this method it is important to check any legislation pertaining to your area because the use of hormones in fish farms are restricted or even banned in certain parts of the world. Also check the market situation; you don’t want to find out too late that the consumer segment you’re aiming for dislike hormone treated food.