Biodiversity & Conservation

By-the-wind-sailor - Velella velella

Velella velella

Image Keith Hiscock - Velella velella stranded on a sandy shore. Image width ca XX cm.
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Distribution map

Velella velella recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

Why do the maps differ?

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Velella velella is not listed under any importance categories.

Taxonomy icon Taxonomy Taxon English term
Phylum Cnidaria Sea anemones, corals, sea firs & jellyfish
Class Hydroidomedusa
Authority (Linnaeus, 1758)
Recent synonyms Velella spirans
Map icon Recorded Distribution in Britain and Ireland Velella velella is an ocean dwelling species that is occasionally seen in the open sea and washed up around British and Irish coasts (see additional information below).
Habitat information icon Habitat information Velella velella is a pelagic species but is occasionally seen washed up around Britain and Ireland.
Text page icon Description Velella velella is a pelagic colonial hydroid. The float, which is an oval disc, is deep blue in colour and can be up to 10 cm in length. Short tentacles hang down into the water from the float. A thin semicircular fin is set diagonally along the float acting as a sail. This sail gives the animal both its scientific (i.e. from velum, a sail) and its common name, 'by-the-wind-sailor'. The direction of the sail along the float determines which way Velella velella will travel. If the sail runs north-west to south-east along the float it will drift left of the wind direction, if the sail runs south-west to north-east it will drift right of the wind direction. Velella velella feeds on pelagic organisms, including young fish, caught by stinging cells on its tentacles. The sea slug Fiona pinnata , sunfish Mola mola and violet snail Janthina janthina prey upon Velella velella.
Identifying features
  • Deep blue oval float up to 10 cm in length.
  • Semicircular sail set diagonally along float.
  • Short tentacles hanging down from float
  • Left sailing and right sailing forms.
Additional information icon Additional information Velella velella is commonly found on the surface of the warmer waters of the World's oceans (Kirkpatrick & Pugh, 1984). McGrath (1985; 1992) reported large numbers of Velella velella washed up around the west coast of Ireland each year between 1976-1984, and again in 1992. In 1981 strandings were reported along the north Cornish coast, in north Devon, Lundy, Weston-Super-Mare and south-west Wales (Turk, 1982b). The Cornish Wildlife Trust Strandings Index (2002) has reports of two main stranding events per year in the winter, December-February, and late summer early autumn, August-September.

In 2002 there were numerous reports of washed up Velella velella. John White reported Velella velella washed up on a Sussex beach at Bognor rocks and Robert Harvey reported the species as far north as Kilmory Bay in the Sound of Jura (BMLSS, 2002a). Mike Bates reported Velella velella being washed up on the south of the Isle of Man, the last confirmed record previous to this was in 1954 (BMLSS, 2002a). At Millport, on the Isle of Cumbrae, Philip Smith reported small numbers of Velella velella washed ashore (BMLSS, 2002a), the first record from the Isle of Cumbrae despite there being a marine station there for over a hundred years (Smith, pers comm.). Edwards (1959) reported living specimens of Velella velella at Croy Sands, Turnberry Bay but no specimens were found on the Isle of Cumbrae despite a search.

This review can be cited as follows:

Olwen Ager 2008. Velella velella. By-the-wind-sailor. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 27/11/2015]. Available from: <>