Warm water aquaculture in Asia has reached a scale that we can only dream about in Africa. Six Asian countries – China, Taiwan, Vietnam, Malaysia, Bangladesh and Thailand – contribute large volumes of freshwater fish and shrimp to the world market. I recently visited Nam Sai tilapia hatchery in Thailand to see if its methods could be applied in our part of the world.
Most farms in Thailand are situated in the country’s central southern region. This flat, well-watered lowland is used largely for rice farming. Abundant water is available from several large rivers. Nam Sai is developing seven strains of genetically improved tilapia for local and international use. The area has a tropical climate and water temperatures vary from 26°C to 32°C, the preferred range for optimum tilapia growth.
Ponds can be more than 1ha. Extensive use is made of hapas, enclosures made of small-mesh blue netting staked at the corners into the shallow ponds. The fish are confined to the hapas, which makes them easy to catch. The nets are used for breeding adult fish, as well as rearing fry and fingerlings.
All the fry distributed for on-growing are sex-reversed, using the tried-and-tested hormone-feed method. Interestingly, this is done in green water ponds, where water is enriched to produce phytoplankton and zooplankton blooms that provide feed for the tiny juvenile fish.
A pole under the netting crowds the red tilapia to one end for sorting.
Removing eggs from the mouths of mouth-brooding female tilapia. The eggs are placed in shallow trays of water, and later moved to incubators.
Hatched fry incubating in trays while they absorb the yolk sac.
Can these methods work here?
The Asian pond culture system used to grow our African tilapias is simple, yet clever. Can it be applied in South Africa?
Unfortunately, most of our country lies on a high plateau, with altitude contributing to cooler nights and winters.
Growth rates are thus slower than in tropical Asia. Water temperatures favouring rapid growth only occur during six to eight months of the year.
The lowland areas of northern KwaZulu-Natal, parts of the Mpumalanga lowveld and the lowlands of Swaziland and Mozambique are the only regions even remotely suitable for such pond fish culture. Most of these areas are close to wildlife reserves with diverse populations of avian and other predators, so it’s essential to protect the tilapia concentrated in ponds if harvests are to be substantial.
Excellent water Quality
Essentials for pond aquaculture are suitable flat land, clay soils that retain water and adequate quantities of water to keep the ponds full. Production can vary from 5t to 10t tilapia/ha, depending on the feeding level and whether the water is fertilised using manure or chemical fertilisers. What is attractive about Asian pond aquaculture techniques is the fact that there is very little equipment required, the water quality in ponds is usually excellent and there is a lower incidence of disease.
The fish harvested tend to be fat and healthy, and the system is relatively forgiving of mistakes – thanks to the high volumes of water involved. In our arid country, suitable land and sufficient water is often in short supply. What I particularly like about the Asian aquaculture system is its simplicity and the make-a-plan attitude of the producers. For all their casual attitude, they adhere strictly to the basic principles of aquaculture husbandry and their management is anything but haphazard.
Nicholas James is an ichthyologist and hatchery owner. Contact him at [email protected]. Please state ‘Aquaculture’ in the subject line of your email.