Mention the words Nile tilapia and most warm-water aquaculturalists get a misty-eyed and wistful look. This is because the species Oreochromis niloticus (Nile tilapia) has become the species of choice for global commercial aquaculture.
In much the same way we farm chickens, which have been genetically developed to produce higher yields of eggs and meat, current Nile tilapia have been genetically improved to produce more over a shorter period of time.
Nile tilapia was first farmed around 1980, although there is evidence that ancient Egyptians kept them in ponds next to the Nile 3 000 years ago. During the Second World War, Oreochromis mossambicus was dispersed throughout Southeast Asia.
Subsequent farming attempts revealed the limitations of early maturity, slow growth and poor body shape in this species. As such, an alternative was sought.
Nile tilapia were sourced from Lake Manzala in Egypt and warm water sources in Abasa, Ghana, and formed the basis of a breeding programme developed by WorldFish, an international research organisation in the Philippines.
At this stage, Nile tilapia was the equivalent of the chicken of the 1960s; while it performed better than any other fowl, there was room for improvement. For example, broiler chickens in the 1960s could grow from day-old chicks to around 400g in six weeks.
Today’s broilers can gain over 1kg during the same period, which is a remarkable testimony to their genetic improvement.
Likewise, Nile tilapia was initially developed to produce the genetically improved farm tilapia (GIFT) strain, which came about in 1990 after 10 years of selective breeding. This strain grew 30% faster than its ancestors.
Modern Nile Tilapia
Since then, GIFT has developed even further, and has now passed its 14th generation of selection. As a result, other strains have emerged, including the Chitralada, Big Nin and Super Black.
Red strains of tilapia owe their ancestry to the occasional xanthic individuals found in O. mossambicus. Hybridised with Nile tilapia, these red colours can be fixed and then linebred to improve the strain.
All plants and other living organisms appear to show occasional xanthic colour forms (red paw paws and grapefruit are examples).
In tilapia, these are attractive enough to serve as a marketing gimmick, and a red tilapia resembles a red sea fish like snapper or roman, giving it a price advantage.
Most modern tilapia strains are also selected for disease resistance. Streptococcus outbreaks have also had an impact on tilapia farms in Asia, and efforts to develop strep-resistant strains are underway.
Likewise, the virus TiLV (tilapia lake virus), which seemed to emerge from the Sea of Galilee in Israel, is causing concern as commercial stocks are impacted with high mortalities.
As with many diseases that affected domestic animals, strains will be developed that can resist these.
However, the use of other tilapia species, or even ancestral Nile tilapia, runs the risk of spreading disease to wild forms and nullifies the efforts made by selective breeding