Bloecher, Olsen, and Guenther conducted detailed field measurements at commercial salmon farms in central Norway to quantify the relationship between net biofouling and fish production performance. Over two complete production cycles, the researchers monitored fouling biomass accumulation on cage nets alongside concurrent measurements of water flow velocity through the mesh, dissolved oxygen concentrations inside pens, fish feeding behaviour, growth rates, and mortality.
The data revealed a clear dose-response relationship: as fouling biomass increased, water exchange through the net declined proportionally, leading to localised oxygen depletion within pens — particularly at depth and during slack tide. Fish in the most heavily fouled pens showed feed conversion ratios 8 to 15 percent worse than those in recently cleaned pens, along with higher incidence of gill pathology and elevated background mortality. The economic implications were substantial, translating to an estimated loss of 0.3 to 0.5 euros per kilogram of harvested fish at heavily fouled sites.
These findings underscore the importance of maintaining adequate cleaning schedules — the fouling season calendar offers regional guidance on timing. Use the biofouling cost calculator to estimate production losses from delayed cleaning, and consult the guide to biofouling and fish health for practical mitigation strategies.