Aquaculture & Fish Nutrition

Why aquaculture matters globally and in South Africa

In 2022 global aquaculture production reached 94.4 million tonnes and overtook capture fisheries for the first time, supplying 51 % of all aquatic animals consumed by humans. South Africa's domestic aquaculture sector remains small (≈ 6 000–9 000 tonnes/year) but tilapia and African catfish are identified by DFFE's Aquaculture Development Strategy as the highest-potential warm-water species.

What 'balanced feed' actually means

The NRC (2011) Nutrient Requirements of Fish and Shrimp defines the digestible protein, amino acid, lipid, mineral and vitamin requirements for the major cultured species. For Nile tilapia in grow-out, a digestible crude protein of 28–32 % with a digestible energy of ~12–14 MJ/kg, and lysine ≥ 1.4 % of dry diet, produces a feed conversion ratio (FCR) of 1.4–1.8 under good husbandry.

Stocking, growth and welfare benchmarks

• Tilapia grow-out: 1.4–1.8 g/day at 28 °C with DO ≥ 5 mg/L (UVI long-term data).
• African catfish (Clarias gariepinus): tolerates DO down to 3 mg/L thanks to its accessory air-breathing organ — one reason it is South Africa's most resilient warm-water culture species.
• Stocking density: 60–80 fish/m³ in the rearing tanks of a UVI-style commercial system is well-supported by long-term data.

Ethics, sustainability and the FIFO problem

A long-running critique of aquaculture is the fish-in/fish-out (FIFO) ratio — feeding wild-caught small fish to farmed fish. For tilapia and catfish, the FIFO ratio is already < 0.5 and improving as plant-protein, insect-meal and single-cell-protein replacements scale. This is one of the strongest sustainability arguments for warm-water freshwater aquaculture over carnivorous marine species.

“Aquaculture has overtaken capture fisheries as the main producer of aquatic animals for human consumption — and freshwater species like tilapia and catfish are leading that shift on a low feed-conversion footprint.”

— FAO SOFIA 2024