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From humble beginnings: Dusky kob farming in SA


By Nicki Holmyard


South Africa is Africa’s most advanced economic powerhouse, a member of the emerging market/ economic block BRICS, and an advanced gateway to the continent.

The country is also one of the biggest seafood producers, importers, exporters and distributors, and has well developed transport networks for fresh and frozen products.

However, with a total production of just over 4,000 metric tons of farmed seafood produced in 2013, aquaculture to date has not been high on the South African agenda. But times are changing, and with recent government investment, there are now reasonable prospects for increased production of the main species; tilapia, abalone, mussels, trout … and dusky kob.


Dusky Kob

Family: Sciaenidae
Genus: Argyrosomus
Species: japonicas
Environment: Marine, brackish, benthopelagic, oceanodromous
Depth: 1-120 meters
Climate: Sub-tropical, 22 deg S-38 deg S, 14 deg E-29 deg E
Diet: carnivorous
Size: Maximum 181cm, common to 80cm
Average EU market price: €6/kilo in 2013
Main producers: South Africa, Mozambique, Australia
Market size: 0.8 kilos-2.5 kilos
Production methods: intensive
Production systems: cages, ponds
Growth: 1.11kg in 12 months at 22 deg C


Not the world’s most well-known fish, dusky kob (Argyrosomus Japonicus) — primarily a game fish found in estuaries and close-shore waters along the coast of South Africa — is the species of choice for South African fish farm Oceanwise.

The company has been rearing this species with varying degrees of success for 12 years using a marine recirculation system, which allows it to supply fish all year round.

The business is located in the East London Industrial Development Zone, which is adjacent to the ocean.

The original broodstock were taken from the wild and the first successful spawning achieved in 2009. The company now has 27 of the original brood fish and 50 first generation fish, which form its spawning management program.

Broodfish are conditioned to spawn on a regular basis, and the eggs fertilized, incubated and hatched in state of the art facilities. Live feed are produced in-house to feed the larval stages, and the fry are weaned onto formulated diets.  Harvested fish are sold whole fresh gutted and gilled, as whole frozen fish and frozen fillets.

From a flying start, the company has been addressing production and finance issues over the past year and now appears to be back on track.

For example, its rate of algae production was constraining the hatchery production and this has now been increased from 15 to 30 cubic meters to support increased rotifer production. This in turn has scaled up from a batch capacity of 70 million to 200 million.

The larval rearing capacity is now 5.4 million, up from 600,000, which will provide a sufficient seed supply for grow out, and create a stronger culling opportunity for better selection of fast growers. This in turn will improve the efficiency and productivity of the company.

Feed, one of the highest costs of production has been reduced by around ZAR6 (US$0.49/€0.44)/kg by switching feed companies, and the price has dropped from ZAR20.50 (US$1.69/€1.50)/kg to ZAR14.53 (US$1.20/€1.06)/kg. This will deliver a reduction in costs of more than ZAR2m (US$164,665/€146,246) per year.

Better controls have also been introduced into the production system, including a computerized Biomass Management Program, which assigns accountability on a tank-by-tank basis.

Oceanwise farmed kabeljou has been established as a recognized premium sustainable seafood in a number of South African retail and food service outlets and hotels, and sales have been helped by the green WWF-SASSI status it has been awarded. It is also on the airline menus via LSG Skychefs, of Lufthansa, Air France, Swiss Air, Virgin Airways, Etihad, Airways and Emirates.

Interest is also strong from export markets in the EU, United States, Canada, Hong Kong, China, and Japan, which are expected to take off once volume has built up.