Aquaculture in Africa: A Copper-Alloy Net Trial at Cahora Bassa, Mozambique

MozamFishFarmAlthough aquaculture is a relatively new industry in Southern Africa, significant growth and adoption of technologies are helping to feed many in the region.

Sub-Saharan Africa is comprised of 49 countries and has a population of more than 853 million people. This vast region has the world’s highest population growth and according to reports, it is also the world’s hungriest.

Fish have been, and still are (where available) the prime source of protein for many living in the sub-Saharan. However, as natural fish resources are depleted, “the gap between supply and demand is increasing at an alarming rate,” according to Evert Swanepoel, Director of the Copper Development Association Africa, South Africa. Studies show that the fish deficit in sub-Saharan Africa can only be met by successful development of the fish farming industry.

Cahora Bassa, Mozambique

Cahora Bassa Lake in Mozambique is Africa’s fourth largest artificial lake. In the 1960’s the Cahora Bassa system, a large hydroelectric generating station, was launched by the Portuguese and the Overseas Province of Mozambique. Today it remains the largest hydroelectric power system in Southern Africa.

Technology continues to enhance the lives of South Africans as farmers, entrepreneurs and scientists work together to discover new and innovative ways to tap into the vast natural resources of the Cahora Bassa.

Copper Net Trials in Cahora Bassa

One example of a regional vital resource is the Mozambezi Tilapia Fish Farm in the Cahora Bassa. The farm had been using synthetic nets that were prone to bio-fouling. High nutrient-loading from rivers around Lake Kariba spill into the Cahora Bassa. The nutrients were clogging the farm’s nets containing Tilapia.

The bio-fouling of the synthetic nets resulted in low growth rates of the fish, disease, and high mortalities, particularly when the Tilapia were moved for net-cleaning procedures – a labor-intensive maintenance activity required weekly. Bio-fouling also restricted the flow of water through the nets depriving the fish of oxygen and vital nutrients. This increased the possibility of disease and a reliance on antibiotics for the fish. The synthetic nets were also prone to predator attacks by crocodiles, sharks and otters.

In 2010, the Copper Development Association of Africa and Advance Africa, a company specializing in aquaculture, initiated copper net trials at the Mozambezi Farm. Following the launch, farm managers noted that the copper nets were not prone to bio-fouling or to predator attacks. In May of 2013, the copper nets were populated with 13,000 Tilapia. In November of 2013, the fish were harvested with favorable results:

  • At harvesting the fish weighed on average 50g.
  • Each of the fish were healthier and heavier than those harvested previously and the FCR (food conversion ratio) was better than the FCR of the fish in the adjoining synthetic nets
  • There was no need to remove or traumatize the fish to clean the nets, resulting in lower operating costs and fewer fish mortalities.
  • During the growth trial period crocodiles attacked the synthetic cage and caused major damage but the adjoining copper net was unmarked.

Advance Africa has agreed to work with Stellenbosch University to deploy the next copper-alloy net in Richards Bay, at the Department of Science and Technology-funded Kob Farming Facility in September 2014.