Aquaculture

Copper in Aquaculture

Copper Cage Trials in Richards Bay

Advance Africa was contracted by the Copper Development Association Africa (CDA) to test the suitability of copper alloy aquaculture nets, in comparison to high-density polyethylene (HDPE) nets, in Richards Bay.

The trial was undertaken in association with Stellenbosch University’s Aquaculture Division.

Copper alloy mesh provides several key advantages over conventional HDPE aquaculture nets, including: high resistance to biofouling in saltwater, improved dissolved oxygen levels, reduced parasite load, reduced infections and higher production as a consequence of these advantages. Copper alloy mesh is strong, provides protection from predators, has lower maintenance costs, and can be recycled.

The Stellenbosch Aquaculture project in Richards Bay aims to grow-out dusky kob (Argyrosomus japonicas) from 5g fingerlings to a weight of 1.5 – 2 kg. The trial will compare growth, FCR, and operational costs of holding fish in copper cages as opposed to HDPE cages.  The duration of the experiment is approximately 9-11 months.

 

The project forms part of a long history of work performed by Advance Africa for CDAA including biofouling trials in South Africa, Mozambique and Seychelles, comparative trials on oyster growth and copper accumulation in Algoa Bay, and comparative growth trials of Nile tilapia in cages in Lake Cahora Bassa, Mozambique. These trials are explained briefly below.

Copper Net Trial at Pemba, Saldanha and Seychelles

Together with CDAA, Advance Africa conducted extensive trials on the use of copper alloy mesh in aquaculture grow out cages to determine the biofouling rate of various mesh materials. Cage panels were constructed and various net materials and copper alloys were attached to these and deployed in the ocean in Pemba, Saldanha & Seychelles, where they were monitored and the biofouling rates evaluated.

Cahora Bassa Tilapia Copper Alloy Cage Trial

Advance Africa, Copalcor, CDAA and Mozambezi Tilapia farm undertook a trial to determine the feasibility of using copper alloy mesh for fish grow out cages to combat biofouling and predator issues currently encountered at Cahora Bassa, Mozambique.

Saldanha Bay and Algoa Bay Oyster Trial

Together with CDAA, Advance Africa embarked on a trial to investigate the effect of copper alloy nets on growth, survival and metal accumulation in Pacific oysters (Crassostrea gigas) in Algoa and Saldanha Bay, South Africa. Biofouling in the South African oyster industry (especially in Saldanha and Algoa Bay) is a major operational constraint.

Approximately four hundred 30g oysters were deployed at each site in each treatment for a period of 60-80 days. Lantern nets were constructed using two copper alloys (Wieland and UR3) and standard HDPE. Biofouling was significantly lower on the copper alloy lantern nets.