Biofouling on salmon net pens - the accumulation of organisms like mussels, barnacles, and algae - creates structural and water quality problems that can compromise fish welfare.
Reduced water flow from biofouling creates areas of low oxygen concentration within pens, particularly near the net walls where fish congregate. Salmon experiencing chronic hypoxia show elevated cortisol, suppressed immune function, and reduced growth. Net cleaning procedures - whether mechanical or chemical - temporarily disturb the fish and can cause scale loss. The welfare impacts compound when biofouling issues coincide with warm water temperatures that already stress salmon.