South African aquaculture seems to be bedevilled by systems that are incorrectly or inappropriately designed. This applies equally to extensive pond aquaculture and intensive recirculating systems. It is difficult to understand why so many aquaculture entrepreneurs spend money on systems that fly in the face of overseas success stories. A wealth of information is available on successful systems in neighbouring countries and highly productive systems in the Far East.
A government development department recently asked me to comment on its ‘newly-developed’ pond system for rural aquaculture. The plan proposes ponds between 30m to 50m in length, about 8m in width, and with a depth of 1m. The water is stagnant and filtration is limited to some reeds and plants at one end.
I was asked what kind of production could be expected, with the clear inference that yield was expected to be in tons, not kilograms per year. My answer of about 150kg per pond a year drew gasps of disbelief. They simply did not believe me, and the project is going ahead. Inevitably, it will prove to be yet another aquaculture failure.
Bigger is always better
Extensive pond aquaculture should only be undertaken on a large scale. Anything less than a group of five half-hectare ponds (2,5ha under water) is essentially a pilot project, and will have a production of under 10t a year, even if adequately managed. Twice this volume could be achieved with supplemental feed and additional infrastructure such as mechanical aeration. At a sale price of R40/kg, a 2,5ha farm could theoretically realise R440 000 per year gross income.
This sounds attractive until capital costs are deducted. These include operational expenditure for 10 to 12 months, as well as hidden costs: salaries, harvesting, transport and associated infrastructure, such as buildings and fences. As with any project, there is a critical mass after which it does become profitable, but this depends on the specific project.
An inappropriate tunnel design
A recently distributed circular stated that an intensive tunnel-based system using a 39m x 10m tunnel, complete with heating, filtration and aeration, had the potential to produce 2t of tilapia per month. It would cost R2,2 million, including management costs, but excluding capital repayments. I question whether any tunnel-based tilapia system with such a small footprint could sustain this level of production, as it implies a standing stock of about 12t in the system at any time.
Therefore, this can only be a high-tech, high-risk and over-capitalised design, which is unsuitable for the country at present. Is this yet another example where no operational proof of the system’s success can be demonstrated prior to the investor parting with his cash? We do not need any more home-grown aquaculture failures!
Nicholas James is an ichthyologist and hatchery owner.