Balanus perforatus (Acorn barnacle)


Type of fouling organism: Barnacle

Barnacles are a unique, and much modified group within the Phylum Crustacea. All barnacles are sessile marine animals, which remain fastened to hard substrates. When the barnacle is immersed under water, the upper shell plates open and the legs reach out casting a food collecting net. These basket like limbs are called cirri and filter food from the water and direct it towards the mouth. Barnacles have both male and female organs (hermaphroditic) and are all able to fertilise one another. As the adult stage is sessile, motile larval stages living in the plankton are the main method of dispersal. Barnacle larvae develop through a number of planktonic stages with the rate determined by feeding rate and temperature.

Balanus perforatus is a darkly coloured volcano shaped barnacle with a small oval shaped aperture. It has a calcareous base that can be up to 30 mm in diameter. Larger individuals are found in the subtidal and plates protrude above the operculum. The shell is comprised of six purple plates which are often vertically ridged.

Environment and Habitat

- Found from the mid-shore intertidal down into the shallow subtidal on hard substrates.
- Quite common on wave exposed shores.
- Filter feeder.


- Reproductive type: Hermaphrodite.
- Reproductive frequency: Annual.
- Time of first gamete: November.
- Age at maturity: 1 year.
- Fecundity: 400 - 10,000 eggs per individual.
- Development: Planktonic.
- Larval duration: 1 - 2 months.


- Solitary.
- Permanently attached.


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

Effects and Impacts

- Problematic for stock species as can compete for space and resources.
- Can obstruct the opening of bivalve shells.
- Can reduce the value of shellfish.
- Increases the weight of equipment.
- Increases labour and production costs as a result of cleaning and removal of biofouling.

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


- Widespread throughout south east England and south to West Africa and the Mediterranean.


Skewes, M., 2006. Balanus perforatus. An acorn barnacle. 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/Balanusperforatus.htm

Christophe Naslain (2003) Balanus perforatus Sea Life Centre biology/biology.php?langue=uk&action=detail&bio_id=279

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

Herbert et al (2003) Range extension and reproduction of the barnacle Balanus perforatus in the eastern English Channel. JMBA(UK) 83:73-82.

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

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