Due to its inherent corrosion resistance and mechanical properties, copper alloys are ideal materials for both surface and submersible marine aquaculture enclosures for near- and off-shore sites.
Copper alloy mesh aquaculture pens improve the sanitary conditions, productivity and sustainability of operations for farmers raising a variety of species.
Exclude Predators and Prevent Escapes
The high-strength copper alloy mesh resists predator attacks and eliminates escapes of farmed fish, decreasing the direct economic cost to fish farmers and preventing the ecological impact of any interbreeding with wild fish stocks. It has also shown resilience against extreme storms.
Maintain Pen Volumes
Copper alloy mesh provides structural stability that allows pens to maintain their shape and volume in strong ocean waves and currents. This prevents fish crowding and helps maintain high oxygenation that ultimately improves yields. The mesh also possesses high mechanical strength and formability, which is essential in the manufacturing of effective marine aquaculture containment structures.
Improve Fish Health and Production
Copper alloys exhibit low macro-organism attachment in seawater which leads to cleaner mesh pens. This reduces the costs, fish stress and nuisance associated with conventional net changes. The resulting increased water exchange and dissolved oxygen improves fish health and welfare, leading to increased growth and development, lower mortality rates and improved feed conversion.
Copper alloy mesh rarely needs to be cleaned and eliminates the need for routine net changing, lowering overall costs associated with maintenance and diver risk.
Long-lived and Recyclable
Copper alloy mesh lasts for six years or more depending on application conditions. It loses little mass over time, and is fully recyclable. Recycled material is used in initial production of copper alloy mesh, which further reduces CO2 emissions, compared with traditional polymer nets. High-strength and corrosion-resistant copper alloy meshes are compatible with pens commonly used in the marine aquaculture industry, allowing for rapid implementation at existing grow-out centres.
Current Use and Future Applications
Copper alloy mesh technology began in 1975 with small salmon farming enclosures in the north-eastern USA. Since then, alloy technology has evolved and is now being successfully used in Australia, Canada, Chile, China, Greece, Japan, Korea, Mozambique, Scotland and the Seychelles, providing productive and sustainable solutions for fish farmers.
Three alloys are currently commercially available: copper-zinc, copper-nickel and copper-silicon.
Copper-zinc is good for flexible mesh containment systems.
Copper-nickel is good for rigid (e.g. welded) mesh.
Copper-silicon is good where rigid mesh is needed, or where panels can have flexible connections.
After exposure to seawater, copper alloys develop a surface oxide film which provides protection from corrosion.
Copper alloy mesh can easily be used for all current commercially-available cage designs as well as other innovative fish cage systems.
Copper alloys can harbour slimes, but the attachment of macro-organisms—such as marine grasses and shellfish—is impaired. If these do become attached under quiet conditions, adherence is poor and they can be easily removed mechanically. Copper alloy mesh prolongs the intervals between periodic cleaning, thus promoting a cleaner and healthier environment for aquaculture.
The exact cost of using copper alloys in aquaculture enclosures depends on multiple factors such as the cage size and the transportation of materials to the construction site, and then of the cage to the farming site. Overall, the total cost is offset by the long-term cost savings associated with longer service life, decreased fish losses, lowered maintenance, improved Food Conversion Ratio and reduced health costs.