Tassal farms Atlantic salmon in Tasmania, with the salmon typically contained using a single layer of netting constructed from polymeric (filament) fibres. These nets have approximately a 6 year lifespan during which time the breaking force for the strongest nets used decreases from 300 kg to around 160 kg. The nets are often damaged by predators (sharks and seals) attempting to take salmon from inside the nets.
There is evidence that sharks can bite and cut through the net but there is no direct evidence that seals damage the nets through biting (but this cannot be discounted). It would appear that seals tend to work on a hole or weakness through repeated nose/head punching at the aperture in an attempt to snare fish as they swim past. The seals also attempt to extract dead fish by the head or tail through the netting apertures.
Net damage and consequent stock loss is a major problem that Tassal wishes to address. Tassal has tried numerous netting systems to address the issues including wire netting, fine wires interlaced within the polymer netting structures, high strength fibre (e.g. Dyneema), plastic meshes etc all without commercial success (based on cost, practicality, poor service life due to corrosion etc.).
One approached currently being investigated by Tassal, which is showing promise, is the use of a stiffened polymer fibre netting material provided by a Japanese company. This product is expensive but not unacceptable if it provides a solution. However supply of this netting appears restricted and the company cannot currently supply to Tassal requirements. Based on the production process of the Japanese supplier, mesh sizes and netting width is limited.

Commercial in confidence. To know more about this project please contact FRDC.