Electra pilosa forms thin, white, encrusting colonies with zooids that bear a distinctive ring of long spines around the frontal membrane — giving the colony a “hairy” texture visible under slight magnification. Colonies spread as irregular patches, typically 1–2 mm thick, across kelp blades, bivalve shells, and synthetic aquaculture materials. The species ranges from the Arctic through Scandinavia, the North Sea, and the British Isles, and extends into the western Baltic Sea. It favours depths of 0–30 m and tolerates salinities above 15 ppt.
On aquaculture nets and ropes, Electra colonies roughen the surface and increase frictional drag. Though individually thin, they often co-occur with Membranipora, spirorbid worms, and barnacle recruits, forming a composite hard-fouling crust that stiffens netting, accelerates twine abrasion, and complicates removal. On shellfish — particularly mussels — Electra encrustation along the shell margin can interfere with valve opening and reduce growth rates by 5–10 % in heavy infestations.
Air-drying for 12–24 hours kills colonies, and the dead crust flakes off during subsequent handling. Mechanical scraping removes established growth but releases calcareous fragments. Anti-fouling coatings reduce settlement during the summer breeding season (May–August in northern Europe). Because Electra contributes to a broader hard-fouling community rather than causing problems in isolation, managing it alongside other encrusting species through an integrated anti-fouling programme is the most practical approach. For more on bryozoan fouling, see the organisms database and our blog.
Control Methods
Air-drying Mechanical scraping Anti-fouling coatings