Biofouling

Biofouling is the unwanted accumulation of microorganisms, algae, barnacles, mussels, and other sessile organisms on submerged farm structures, including net pens, cage netting, mooring lines, intake pipes, and sensors. The fouling community develops within days as a bacterial slime film and progresses to macrofouling within weeks in warm productive waters, progressively clogging mesh openings, adding weight and drag to cages, and restricting water flow through nets and pipes. Consequences are operational and biological: reduced water exchange inside net pens lowers dissolved oxygen at depth, heavier fouled nets stress moorings in storms, and clogged intake screens starve pumps. Control methods include in-water net changing and cleaning with high-pressure washers, antifouling net coatings and copper-alloy nets, and for pipelines, periodic chlorination or pigging. Cleaning frequency is a trade-off between labour and dive-safety cost and fish welfare, and cleaning events must be scheduled to avoid stressing fish during sensitive periods such as sea lice treatments or high temperature. Biofouling also transfers invasive species between sites, so some jurisdictions regulate fouling management on vessels and cage equipment moved between farming areas.