Net cleaning is the single largest biofouling-related expense for salmon cage farmers. The numbers are substantial, and they compound over a typical 18-24 month production cycle.
A modern in-situ net cleaning machine — the type that operates underwater while fish remain in the pen — costs between 200,000 and 500,000 euros to purchase, depending on size and capability. Operating costs add up: fuel for the support vessel, crew wages, maintenance of the cleaning heads and hydraulic systems. A typical Norwegian salmon farm with 8-12 cages may spend 50,000-100,000 euros annually just on cleaning operations.
But the direct cleaning cost is only part of the picture. Each cleaning event disturbs the fish, triggering a stress response that temporarily reduces feeding. Fish can stop eating for 12-48 hours around a cleaning operation. Multiply that by 20-30 cleaning events per production cycle and the cumulative lost feeding time becomes meaningful. There is also the fouling debris released during cleaning — organic waste and fragments that sink to the seabed beneath the farm, contributing to benthic loading that regulators increasingly scrutinise.
Alternatives to in-situ cleaning carry their own cost profiles. Net changing — removing fouled nets and replacing them with clean ones — requires spare net inventory (each net costs 15,000-40,000 euros), crane time, and labour. Copper alloy nets eliminate most cleaning needs but cost 3-5 times more than nylon nets upfront. Silicone foul-release coatings reduce cleaning frequency but must be reapplied every 2-3 years. Compare all options in the anti-fouling methods comparison.
The CRAB Project estimated that biofouling management accounts for 5-10% of total salmon production costs (Lane and Willemsen, CRAB Project Report, 2007). For a farm producing 5,000 tonnes annually at a production cost of 4-5 euros per kilogram, that is 1-2.5 million euros per year spent managing fouling — through cleaning, coatings, net replacement, and the indirect losses from reduced fish performance. Use the cost calculator to model these figures for your own site.
The farms with the lowest overall fouling bills tend to combine approaches — coated nets that slow fouling growth, plus targeted cleaning when needed — rather than betting on any single method.