International Convention on the Control of Harmful Anti-fouling Systems. Adopted by the IMO in 2001, it banned tributyltin (TBT) based anti-fouling paints on ships worldwide. See our FAQ for more on regulations.
Barnacle
Sessile crustacean (infraclass Cirripedia) that cements itself permanently to submerged surfaces. Common foulers include Balanus crenatus and Amphibalanus amphitrite. Produces calcareous shell plates — a hard fouler.
Benthic Loading
The accumulation of organic matter on the seabed beneath aquaculture sites. Fouling debris released during net cleaning contributes to benthic loading and is increasingly regulated under the BPR.
Biofilm
A thin layer of bacteria and extracellular polymers that forms on any submerged surface within hours. The first stage of the fouling succession — biofilm conditions surfaces and attracts subsequent colonisers. See The Biology Behind Marine Biofouling.
Biocide
A chemical substance that kills living organisms. In anti-fouling, refers to active ingredients (copper compounds, zinc pyrithione) released from anti-fouling coatings to prevent fouling settlement.
Biofouling
The undesirable accumulation of living organisms on submerged surfaces. In aquaculture, refers to organisms growing on cage nets, ropes, buoys, moorings, and cultured shellfish. Browse our organism database or use the cost calculator to estimate impact.
Biocidal Products Regulation (BPR)
EU Regulation 528/2012 governing the marketing and use of biocidal products, including anti-fouling coatings. Requires active substance approval and product authorisation. See also AFS Convention.
Bryozoan
Small colonial invertebrates (phylum Bryozoa) that form encrusting or branching colonies on submerged surfaces. Some species form hard calcareous crusts; others like Bugula grow as soft bushy tufts. See the organisms database.
Byssal Threads
Tough protein fibres produced by mussels to anchor themselves to surfaces. Byssal attachment is strong but not permanent — mussels can detach and re-attach elsewhere.
Calcareous
Made of or containing calcium carbonate (CaCO₃). Barnacle shells, tubeworm tubes, and some bryozoan colonies are calcareous — hard structures that resist removal.
Cleaner Fish
Fish species (wrasse, lumpfish) deployed inside salmon cages to eat parasites and fouling organisms off net surfaces. A form of biological control. Read how cleaner fish are used in salmon farming.
Conditioning Film
The initial layer of dissolved organic molecules that adsorbs onto a newly immersed surface within seconds. Alters surface chemistry and enables bacterial colonisation — the starting point of all biofouling.
Copper-Alloy Net
Cage net made from copper-nickel or copper-zinc alloy wire instead of nylon. The copper surface prevents fouling attachment. High upfront cost but minimal cleaning over a 5-7 year lifespan. Compare with other methods.
Cyprid
The final larval stage of a barnacle. Cyprids actively explore surfaces, testing biochemical cues, before committing to permanent settlement and metamorphosis into a sessile adult.
Diatom
Microscopic single-celled algae with silica cell walls. Among the first organisms to colonise submerged surfaces after bacterial biofilm, forming the visible greenish-brown slime layer (microfouling). See diatom biofilm.
Feed Conversion Ratio (FCR)
The ratio of feed consumed to fish weight gained. Fouled nets increase FCR by reducing oxygen and stressing fish — more feed per kilogram of growth. Estimate impact with our biofouling calculator.
Foul-Release Coating
A non-toxic coating (typically silicone-based) where fouling organisms attach weakly and detach under water flow or light cleaning. No biocide is released. Read about copper-free alternatives.
Hard Fouling
Fouling organisms that produce rigid calcareous or mineralised structures — barnacles, calcareous tubeworms, encrusting bryozoans. Difficult to remove without mechanical force.
Hydroid
Colonial cnidarian related to jellyfish. Hydroids form feathery or branching colonies on net surfaces and are typically among the first macrofoulers to appear. Example: Ectopleura larynx.
In-Situ Cleaning
Cleaning cage nets underwater while fish remain inside the pen. Uses disc cleaners, high-pressure washers, or ROVs. Compare cleaning methods.
Larval Settlement
The process by which planktonic larvae of fouling organisms attach to a surface and begin metamorphosis into sessile adults. Settlement is influenced by surface chemistry, biofilm composition, light, and water flow.
Macrofouling
Fouling by organisms visible to the naked eye — barnacles, mussels, hydroids, tunicates, algae, bryozoans. Distinct from microfouling. Browse all species in our organism database.
Microfouling
The initial fouling stages consisting of bacterial biofilm and diatom settlement. Forms the slime layer that precedes and facilitates macrofouling.
Net Occlusion
The blocking of net mesh openings by fouling organisms. Measured as a percentage — 60 % occlusion means 60 % of the mesh area is blocked. Heavy occlusion raises FCR and stresses fish.
Net Pen
A floating cage structure with nets enclosing fish in open water. Standard setup for salmon, sea bass, and sea bream farming. Nets provide the largest fouling surface area on a farm. See farm map for sites across Europe.
ROV (Remotely Operated Vehicle)
An unmanned underwater vehicle controlled from the surface. In aquaculture, ROVs fitted with cleaning heads are used for deep or exposed sites. Compare manual vs automated cleaning.
Sessile
Permanently attached to a surface. Adult barnacles, tubeworms, and encrusting bryozoans are sessile organisms — once settled, they cannot move.
Recently settled juvenile bivalves (mussels, oysters). In aquaculture, spat settlement on equipment is fouling; on collectors, it is the desired product.
Tributyltin (TBT)
An organotin compound formerly used in anti-fouling paints. Banned by the AFS Convention due to severe environmental toxicity — caused imposex in marine snails and accumulated through food chains.
Tunicate (Sea Squirt)
Marine invertebrate (subphylum Tunicata) that filters seawater for food. Solitary species like Ciona and colonial species like Botryllus are common foulers on aquaculture equipment.
Tubeworm
Polychaete worm that builds a permanent calcareous or sandy tube on a hard surface. Calcareous tubeworms (Pomatoceros, Hydroides, Serpula) are hard foulers; sand-tube worms are softer.
