Type of fouling organism: Hydroid

Hydroids are simple in structure, all are aquatic and most are marine. The life cycle includes both sessile polyps and freely floating medusae, with hydroids formed as the sessile asexual polyp stage with a reduced pelagic free floating sexual medusae or jellyfish stage. In many hydroids, the medusa stage is reduced and remains attached to the hydroid. Some species may even have a swimming polyp stage in the life cycle.

Tubularia indivisa is a large hydroid reaching 100 - 150 mm in height. It has a stem holding a solitary, conical polyp that is brightly coloured with shades of pink and red and flask shaped. The stems stand erect and are fused together with other stems into dense tufts at the base . The polyp looks like a flower and consists of a central cluster of about 40 oral tentacles surrounded on the outside by 20 - 30 paler but larger tentacles. Polyps are often present only in the spring. Tubularia indivisa and Tubularia larynx can be difficult to distinguish and the two often occur together. In Tubularia larynx, the stems branch, while in Tubularia indivisa they are unbranched, though separate individuals settle on the stems of others forming irregular clumps.

Environment and Habitat

- Attaches to hard substrata from the inter tidal to the shallow shore, particularly abundant in areas with strong tidal currents.
- Found on various solid substrates from lower shore rock pools to depths of at least 280 m.

Reproduction

- Reproduction type: Budding separate sexes vegetative.
- Reproduction frequency: Annual.
- Age at maturity: Variable with change between sessile hydroid and free-living medusoid stages in the life cycle.
- Fecundity: Unknown.
- Development: Planktonic.
- Larval settlement time: Variable with life cycle change from sessile to free living.
- Dispersal potential: Unknown.
- Life span: Variable, like other hydroids has the potential to be very long lived.

Communities

- Neat, bushy colonies.

Equipment

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

Effects and Impacts

- Problematic for stock species as can compete for space and resources.
- 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

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

- Widespread throughout the north east Atlantic but not in the Mediterranean.

References

Edwards, R.V., 2007. Tubularia indivisa. Oaten pipes hydroid. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 21/02/2007]. Available from: http://www.marlin.ac.uk/species/Tubulariaindivisa.htm

Tubularia indivisa Linnaeus, 1758 P1 Picton, B.E. & Morrow, C.C., 2005. [In] Encyclopedia of Marine Life of Britain and Ireland
http://www.habitas.org.uk/marinelife/species.asp?item=D1440

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.