Photo: Wikimedia Commons
Originally from the lakes and rivers of Africa, tilapia has spread across most of the world as an aquaculture species with superb qualities, both on the farm and in the kitchen.
Tilapia isn’t actually a species but rather a group of fish from the family Cichlidae, and even includes many species of fish that are popular in the aquarium trade, such as Malawi cichlids. Also included are several species that grow to a size large enough to be eaten, and many of these are farmed.
The Nile tilapia (Oreochromis niloticus) is a species that dominates global fish farming due to it offering fast growth and being well suited to domestication. More than 99% of all farmed tilapia are either pure or hybrids of Nile tilapia. Thus, when the aquaculture industry speaks about ‘tilapia’, it is this single species that is being referred to.
In 2022, tilapia was the third most farmed fish species in the world, and is probably the species that is farmed across the widest geography, as the two main species, grass carp and silver carp, are primarily farmed in China (according to the Food and Agriculture Organization of the UN, see graph), whilst Nile tilapia is farmed across the world.
Tilapia can be farmed in several different types of infrastructure, including earth ponds, cages and recirculating aquaculture systems (RAS), with the choice of species and farming method being guided by the regional climate and the resources that are locally available.
Temperature requirements
Where the climate matches the species temperature requirements for optimal growth, that is a water temperature of 28°C to 30°C for most of the year, cages and earth ponds are preferred. These infrastructure options are less expensive to erect and operate than a RAS.
However, where the climate is cooler, tilapia will generally be farmed in a RAS, which is housed inside a greenhouse tunnel or warehouse that can be insulated from heat loss and be actively heated during the coolest periods to maintain optimal conditions, irrespective of the weather outside.
As they are tough, both in terms of water quality tolerance and disease resistance, tilapia are fitted to being farmed at high densities, making them well suited to RAS and aquaponics systems.
Under high densities, they produce the nutrients that the plants require to perform well, and together the two crops create a more viable business than either would be on its own.
The breeding of tilapia is extremely simple: males and females held together under reasonable conditions will spawn frequently, with the females incubating the eggs inside their mouths. On commercial farms, the breeders are held in a sex ratio of one male per four females, and the fertilised eggs are collected from the females’ mouths every week.
These eggs are placed into incubators where they hatch, and the fry absorb their yolk sac prior to being placed in tanks or ponds for first feeding.
Tilapia are able to digest and utilise nutrients from plant sources, so their feed is often based on maize, soya and wheat, making it less expensive and more environmentally appropriate than the feed produced for carnivorous fish species.
Minimal supplementary feed
The fry and fingerlings of tilapia thrive in earth ponds that are fertilised to stimulate the development of the natural food chain, with minimal supplementary feed necessary. This extensive farming method produces fish at the lowest cost, but is only applicable in suitable climates where the soil and water support the installation of earth ponds.
As the fish grow, they are regularly harvested, size-sorted and stocked into the next tank, cage or pond for further growth. Slow-growing fish are culled and future breeders are only selected from the fastest-growing fish that show a deep body and other desirable traits.
Improved strains of tilapia grow rapidly, achieving 300g (the market size) in six months. Tilapia are sold whole across much of Africa, with a lesser demand for fillets and other value-added treats.
Farmers in the warmer parts of Southern Africa, where average day- night winter temperatures do not fall below 24°C, can consider farming tilapia in either cages if they have access to a large dam or lake, or in earth ponds.
In the cooler parts with winter day-night temperatures below this threshold, farmers can erect RASs to produce tilapia, adding aquaponics to diversify and increase the economic return on investment.
Farming of this hardy and versatile fish is likely to expand, with increasing investment in farms producing tilapia to meet the growing demand for firm white protein.
Leslie Ter Morshuizen designs and builds fish farms across sub-Saharan Africa, trains farmers to manage them optimally and has run his own operations. He is the founder of Aquaculture Solutions. Call him on 083 406 0208, or email [email protected].
