Type of fouling organism: Sea Star

Echinoderms are a group of morphologically diverse animals and the name derives from the animal's spiny skin. They include sea stars, star fish, brittle stars, sea urchins, sea cucumbers and sea lilies. Their size varies from 1cm to 1m in diameter. Over 7,000 species have been described and all are marine. Their body cavity facilitates the development of a water vascular system, which transports sea water within the animal and bears tube feet that are thought to be responsible for food collection, respiration, sensation and movement. The tube feet in sea stars have enough strength to pull open bivalve shells, enabling them to feed on shellfish.

Asterias rubens is the most common starfish found in the north east Atlantic. It has five arms, which are broad at the base and that may be turned up at the ends when active. Colour varies but is usually orange, pale brown or violet. Average size is 100 - 300 mm but some individuals may be up to 520 mm in diameter.

Environment and Habitat

- Intertidal and to depths of 650 m.
- epibenthic commonly found on all coasts particularly on beds of mussel and barnacles or an algal carpets.
- Feeds on bivalves, crustaceans, polychaetes, other echinoderms and carrion.
- High intolerance of desiccation, substratum loss, change in salinity and oxygenation.
- Intermediate intolerance of change in water flow rate, wave exposure and abrasion.
- Low intolerance of smothering, change in suspended sediment, decrease in temperature, decrease in wave exposure, displacement and changes in nutrients.

Reproduction

- Reproductive type: Separate sexes.
- Reproductive frequency: Annual.
- Age at maturity: 1 year.
- Development: Planktonic.
- Fecundity: > 1,000,000 eggs/per individual.
- Larval duration: > 80 days.
- Dispersal potential: > 10 km.

Communities

- Solitary and gregarious.
- Non-migratory.

Equipment

- Mussel rope culture, oyster and suspended pectinid culture.
- Fishnets, cages, pontoons, shellfish trays, tanks, and pipes.

Effects and Impacts

- Problematic for stock species as can compete for space and resources.
- Can open bivalve shells and feed on the stock increasing losses due to mortality.
- Increases labour and production costs as a result of cleaning and removal.

Control/ Strategies and Management

Nets
- Onshore Net washing
- Coatings (Copper sulphate, fouling release coatings e.g. silicon)
- Mechanical cleaning of infrastructure (Disk cleaners)
- Air drying nets
Trays
- 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)
Shellfish
- 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

Distribution

- Found through out the north east Atlantic from Northern Norway to southern Portugal, but extremely rarely found in the Mediterranean.

References

Budd, G.C., 2007. Asterias rubens. Common starfish. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 20/02/2007]. Available from: http://www.marlin.ac.uk/species/Asteriasrubens.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.