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.
Found on plants and inert substrata, from within rock pools in the intertidal down to over 30 m in the subtidal. Colonies appear like featherlike projections from the surface to which they attach. Largest reported colonies can reach 350 mm in length, although more usually are 200 mm. Colony is typically single stemmed, with many long branches running off the main stem of similar length. The stem is brown-black in colour and may be forked in longer lived colonies.
Environment and Habitat
- Attach to algae and hard substrates found in the subtidal.
- Reproduction type: Budding, separate sexes, vegetative.
- Forms lines or groups of raised feather like colonies.
- Found on other biofouling organisms.
Effects and Impacts
- Can reduce the value of shellfish.
Control/ Strategies and Management
Principles of Management
C Combat Settlement
- Common throughout the north east Atlantic and Mediterranean.
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