Electra pilosa (Sea mat)


Type of fouling organism: Encrusting Bryozoan

Bryozoa are sessile colonies of microscopic animals where each animal inhabits a separate box of the cuticle within the colony which is called a zooid. The zooid body has a fixed trunk and a lophophore for food collection. zooids are hermaphroditic. Gametes are passed out through the pores and fertilised eggs are internally incubated. After hatching motile larvae are released and while most are generally of short duration (minutes to hours), some can survive for up to a year in the plankton before settling. Bryozoa are common intertidal and subtidal animals, most are marine but there are some freshwater species.

Electra pilosa form star shaped or broad sheet colonies on a range of surfaces, including algae but most often hard substrates. The colony is made up of individual zooids which are ovate-oblong in shape. Average size of zooids which form sheets is 0.5 - 0.6 by 0.25 - 0.35 mm. When zooid spines get very long the colony can appear bristly.

Environment and Habitat

- Found from low water into the shallow sublittoral to the intertidal to at least 50 m.
- Feeds on phytoplankton, algal, spores.
- High intolerance of substratum loss, smothering and displacement.
- Intermediate intolerance of desiccation, decrease of water flow, increase in wave exposure and decreases in salinity.
- Low intolerance of increase in water flow and suspended sediments, temperature and turbidity changes and decreases in wave exposure.


- Reproduction type: Hermaphrodite.
- Reproduction period: Annual.
- Age at maturity: Unknown.
- Development: Planktonic.
- Larval settlement time April - Nov.
- Dispersal time: Months.


- Colonial.


- Found on other biofouling organisms.
- Stock species particularly shellfish.
- Fishnets, cages, pontoons, shellfish trays, tanks, pipes, ropes and buoys.

Effects and Impacts

- Problematic for stock species.
- Reduces the value of shellfish and competes with them for space and resources.
- Increases the weight of ropes and lines.
- Increases labour and production costs.
- Have been reported to cause dermatitis and eczema in fisherman.

Control/ Strategies and Management

- Onshore Net washing
- Coatings (Copper sulphate, fouling release coatings e.g. silicon)
- Mechanical cleaning of infrastructure (Disk cleaners)
- Air drying nets
- Manual cleaning (scrubbing and/or brushing)
- Low power washing
- High power washing
- Jet washing
- Air drying
- Lowering trays below photic zone during major spatfalls
- Biological Control (Sea urchins and periwinkles)
- Coatings (Copper sulphate, fouling release coatings e.g. silicon)
- Manual Cleaning
- Mechanical Cleaning
- Hot water 55oC for 5 seconds (Stock mortalities of ca 5% with this method)
- Dipping (Freshwater or chemical solution)
- Lowering lines below photic zone during major spatfalls
- Biological control (Sea urchins and periwinkles)
- Coatings (Copper sulphate, spiky coatings, fouling release coatings e.g. silicon)

Principles of Management

C Combat Settlement
P Protect Equipment and Stock
R Remove Biofouling


- Common throughout the north east Atlantic and Mediterranean


Tyler-Walters, H., 2005. Electra pilosa. A sea mat. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 05/02/2007]. Available from: species/Electrapilosa.htm

Electra pilosa P The Marine Fauna Gallery of Norway fauna/Mosdyr/pilosa.htm

Janet Moore (2001) An Introduction to the Invertebrates. Cambridge University Press

Hayward P, Nelson-Smith T & Shields C (1996) Seashore of Britain and Northern Europe. HarperCollins Pubs.

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