Oreochromis niloticus originated in fresh waters of the Middle East as well as sub-Saharan Africa. It is one of the top 5 most frequently cultured species worldwide, mainly reared in Southeast Asia, China, and Africa. Due to its fast growth, it can reach market size in 5-6 months. Its rearing does not come without a toll on the individuals, though. Because maturity sets in early as well, farmers in intensive rearing administer hormones through the feed that renders individuals all male, or genetic engineering results in all-male populations. This prevents unwanted reproduction and the growth deficiencies that come with it. Also, it favours males which grow up to 50% faster than females.
The two most frequently used culture systems are ponds and cages of which earthen ponds, especially irrigation ponds or reservoirs, overlap more with the natural needs of space, density, and substrate than cages. Shelters and shading may also be applied artifically, though. IND are allowed to spawn naturally, i.e., without manipulation and stripping, but there seems to be a trend towards hormonal induction to synchronise spawning or avoid injuries by aggressive SPAWNERS. Aggression is an issue in other age classes as well and does not seem to be avoidable completely; one recommended method - to size grade - is stressful itself. Other husbandry practices like handling and transport impose stress, too, which may be reduced but not avoided. Electrical stunning followed by exsanguination, evisceration, or filleting is availabla but at risk of failing if not executed correctly.
For details see: Dossier & WelfareCheck | farm
