Indigenous species: let’s widen the net for aquaculture

The butter catfish
The butter catfish (Schilbe intermedius) tastes similar to the well-known golden sole found on most restaurant menus.
Photo: Nicholas James

The river catchments of Southern Africa are usually considered to include the Cunene River and Okavango systems and all those south of them, as well as the Zambezi, Kafue, Luangwa and Shire rivers in the central/eastern region.

Within this area are found no fewer than 245 indigenous freshwater fish species. Why are so few of these used in aquaculture?

It is a sad fact that most of Southern Africa’s staple crops and livestock breeds come from somewhere else. Maize originates from what is now Mexico; wheat comes from the Middle East; and sorghum (Sorghum bicolor) comes from north-east Africa.

With the exception of the Nguni and Ankole cattle breeds, domesticated livestock in the region have been bred or developed from imported stock.

Freshwater fish that feature prominently in local aquaculture are trout (North America) and Nile tilapia (North and West Africa), with only the marginally successful sharptooth catfish (Clarias gariepinus) being a local species.

Large local fish
The main rivers of Southern Africa are home to several large fish species. The largest of these, the catfish of the Orange River system and the vundu of the middle Zambezi, undoubtedly have culture potential if current marketing resistance can be overcome.

Many of the warmer rivers are also home to large mormyrid fish species, including the ‘elephant snout’ fish, such as Cornish Jack and Bottlenose, both of which can weigh more than 10kg when fully grown.

These are oily fleshed, but highly palatable fish with few bones and small scales. Unfortunately, little is known of their breeding habits, and they are restricted to water warmer than 17°C in winter.

In the southern region there are seven species of indigenous yellowfish, most of which are familiar to fly-fishermen. The most common is the smallmouth yellowfish (Barbus aeneus) of the Orange/Vaal River system, which grows to about 7,8kg in size. The largemouth yellowfish can reach 22kg.

Such species would surely have aquaculture potential were they not so bony, a complaint also directed at the closely related carp of Europe and Asia.

Other rejected candidate species are eels (impossible to breed), labeo (bony, rather unpleasant tasting mudfish), species of the Distichodus genus (Nkupe and Chessa) from the lower Zambezi and Buzi river systems (edible but bony), and Characins such as tigerfish and African pike (similar characteristics).

Fish that may have potential are the butter catfish (Schilbe intermedius) and the squeaker (Synodontis zambezensis). Although both are small fish growing to not more than about 1kg, their simple skeleton, firm flesh and robust nature make them worth a second look.

Cichlids
Finally, there are Cichlid species, apart from the tilapias, that are of interest. The happies (Sargochromis spp.) of the upper Zambezi (especially S. giardi, the pink ‘happy’, which attains 2,9kg), have potential.

All consume snails in their natural habitat. There is no reason why these species could not be cultivated.

The largemouth cichlid (Serranochromis robustus), well known to anglers and growing to up to 6kg, could also be an attractive species if commercialised.

It is easy to breed in captivity, and a fine eating fish.

Nicholas James is an ichthyologist and hatchery owner.