Warm-water fish farming, or aquaculture, is slowly coming of age in South Africa, but husbandry practices still lag far behind the rest of the world in terms of species selection, stock enhancement and system design. The concept of seed or stock enhancement is so well entrenched in other forms of agriculture that few would question its use.
And, indeed, many fish species farmed around the world, such as trout and salmon, have been selectively bred for decades to produce faster growing, more disease-resistant, better-shaped fish. But why hasn’t this trend been followed locally, with our African fish, the tilapia? Time and again, tilapia aquaculture in SA has failed due to the use of poor quality ‘seed’.
Fingerlings from old government hatcheries have often been employed in the belief that these must be of good quality. However, a closer examination of the facilities inevitably shows there’s been no programme of stock enhancement, and the ancestry of the brood-stock is unknown. In many cases, fish have been sibling-mated for years, some for as many as 35 years!
Wild pure-strain female Oreochromis mossambicus from the Eastern Cape.
This results in inbreeding depression and loss of diversity, health and vigour – problems well known in other forms of livestock farming. It’s for this reason that Mozambique tilapia have earned a bad name in SA aquaculture, supposedly for ‘poor growth rates’, ‘early maturity’ leading to overpopulation of ponds, and ‘poor body form’. But, as we’ll see, this species has a lot going for it.
Three main species are farmed around the world: the Mozambique tilapia (Oreochromis mossambicus), O. aureus and the Nile tilapia (O. niloticus). During the past 20 years, significant progress has been made in the Philippines and Thailand to develop improved strains of Nile tilapia. One result is the fast-growing, deep-bodied genetically improved farmed tilapia (GIFT). These fish are well established in fish farms in many countries, especially in the Far East.
In association with UK universities such as Stirling and Swansea, meanwhile, Thai aquaculturalists have also recently developed highly productive forms of Nile tilapia. These are now being farmed in indoor heated facilities in the UK, meaning fresh tilapia is available in many supermarkets around the country. If the British can farm our African fish successfully, why can’t we?
Egypt, Uganda, Kenya and other countries in West Africa, where the Nile tilapia is indigenous, are using this species successfully. In Southern Africa, the species has been introduced amid controversy, and is being farmed in Zambia and Zimbabwe.
Escapes by limited numbers into rivers such as the Zambezi and Limpopo have seen the species come to dominate the indigenous Mozambique tilapia (called blue kurper in SA). As a result, we have hybridised populations of tilapia in the Limpopo catchment in South Africa. And, when it comes to quality, these fish are in no way the equivalent of those being farmed so successfully in the Far East – far from it!
Ideal for farming
Blue kurper are indigenous to the fresh and brackish waters along SA’s south-east coastal lowlands. In some populations, blue kurper can grow to over 3kg – as large as Nile tilapia. In the southern extremity of their range they can survive winter temperatures as low as 9,5°C – which are lethal to Nile tilapia or the more tropical strains of blue kurper, which die below 11°C to 13°C.
Even at this limit of their natural range, where you’d expect the fish to be environmentally-stressed or stunted, distinct populations are fast-growing, deep-bodied, late maturing and large-sized, with significant aquaculture potential. These strains grow as fast as their more northerly cousins, but at lower temperatures (18°C to 26°C), making them ideal for fish farmers in Southern Africa’s temperate zones.
Nicholas James is an ichthyologist and owner of Rivendell Hatchery near Grahamstown, which raises fish for aquariums, fish-farming and stocking. Contact Nicholas at [email protected]. Please state ‘Aquaculture’ in the subject line of your email.