City University of Hong Kong-HK

Aquaculture Research

The College of Veterinary Medicine and Life Sciences is supporting a research project into the use of copper nets for fish farming. The copper net project, led by Dr. Howard Wong, aims to tackle Hong Kong’s serious biofouling problem, i.e. growth and attachment of marine organisms onto fish nets. Local fishermen spend a lot of time cleaning and replacing nets, a very expensive, labour intensive activity, which also stresses the fish.

There are other detrimental issues associated with biofouling, including reducing the water flow into nets, lowering of oxygen levels, creating additional drag, causing deformation of nets and harbouring of disease agents within the biofouling community which can also directly damage the skin of fish leading to disease and the need to use drugs for treatment. Copper based paints have been used in various parts of the world to combat biofouling but the effect is not permanent with nets requiring re-application frequently and the paint can rub off and end up in the environment. Copper nets, on the other hand, are made of copper alloy with varying degrees of tin, iron, zinc & phosphorus and are more robust but their effectiveness has yet to be tested in Hong Kong.

This research will initially determine whether there is any significant difference between copper nets and non-copper nets, such as commonly used nylon nets, but also stainless steel nets. Three net panels of each material, 1m by 1m will be suspended in the water just under the surface for a period of one month and each net will be examined weekly and weighed to assess the extent of biofouling.

One of the missions of our aquaculture research is to promote sustainable fish farming and help fish farmers minimize the amount of drugs and chemicals deployed. Disease prevention, disease diagnosis and proper nutrition are hallmarks of sustainable farming but so is improved animal husbandry and welfare and this project aims to determine whether the use of copper netting might be worth introducing onto local farms.