Type of fouling organism: Bivalve

Bivalves are molluscs and include species of oyster, scallop, mussel, cockle and clam. All are aquatic and most are marine. Their body is laterally compressed between two halves of a hinged shell. Many bivalves are sedentary with a foot that secretes a number of byssus threads that enables them to attach to the substratum. Feeding is by way of two main ciliary tracts located on enlarged gill surfaces within the mantle which is contained in the shell. Hair-like structures (cilia) produce water currents and trap food particles beating them towards labial palps allowing small particles to be conveyed to the mouth

The Mytilus edulis shell is roughly triangular in shape and is smooth with a sculpturing of concentric lines. The shell colour varies and is usually purple or blue, but brown individuals have also been observed. Average length range is 50 -100 mm and it attaches to hard substrates with hair-like byssus threads.

Environment and Habitat

- Habitat - high intertidal to subtidal, from open coast rocky shores to rocks and piers both in estuaries and sheltered harbours.
- Feeding - bacteria, phytoplankton, detritus, and dissolved organic material.
- High intolerance of substratum loss.
- Intermediate intolerance of smothering, fluctuations in wave exposure and abrasion.
- Low intolerance of desiccation, changes in water temperature and flow, suspended sediment, salinity and oxygenation.
- Heavily preyed upon by sea stars, dog whelks and crabs.

Reproduction

- Reproduction Type: Separate sexes.
- Reproduction frequency: Annual.
- Age at maturity: 1 - 2 months.
- Fecundity: 1 million eggs per individual.
- Development of larvae: Planktonic.
- Larval settling time: 1 - 6 months.
- Dispersal Potential: > 10 km.
- Life span: Dependent on habitat and locality.

Communities

- Solitary and gregarious.
- Found in dense masses of up to 5 layers.
- Commonly fouled with barnacles and seaweed.

Equipment

- Colonize natural and artificial surfaces such as piles, buoys and harbour structures

Effects and Impacts

- Negative effect on infrastructure and equipment.
- Increases weight of equipment.
- Obstructs the flow of water through the net reducing clearance rates, levels of dissolved oxygen and overall fish welfare.
- Increases competition for food and resources.

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

- The range extends from the White Sea past the Barents Sea in the north to southern France in the north east Atlantic.

References

Tyler-Walters, H., 2002. Mytilus edulis. Common mussel. 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: http://www.marlin.ac.uk/species/Mytilusedulis.htm

Common Mussel (Mytilus edulis) Arkive Images from Life on Earth http://www.arkive.org/species/ARK/invertebrates_marine/Mytilus_edulis/more_info.html

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.