BIOTIC

BIOTIC Species Information for Helcion pellucidum
All Taxonomy Biology Distribution Reproduction

Researched by	Dr Harvey Tyler-Walters	Data supplied by	MarLIN
Refereed by	Dr David McGrath
Distribution and Habitat
Distribution in Britain & Ireland	Recorded on all coasts of Britain and Ireland, except the coast surrounding the Wash.
Global distribution	Occurs in Iceland and from north Norway to south Portugal. It is found on the west coasts of Denmark, and Sweden south to Oresund. However it is absent from the Baltic sea and the east coasts of Denmark, Belgium and Holland.
Biogeographic range	Not researched	Depth range	ca +1 - 25 m
Migratory	Non-migratory / Resident
Distribution Additional Information	Studies in south east Ireland demonstrated that the distribution of Helcion pellucidum on the shore depends on its size and age. McGrath (1992) noted that spat settled with a larval shell attached of ca 0.66 mm. Newly settled spat have a preference for lower shore Lithothamnia (encrusting coralline algae) reaching densities as high as 400 per sq. dm in February. As they grow juveniles (up to 1.8 mm) migrate to Mastocarpus stellatus. The juveniles recruit to Laminarians at about 1.8 mm but are found mainly at the tips of the fronds. Juveniles up to 3 mm may also be found on the receptacles of %Himanthalia elongata%. Dense populations may be found on Fucus serratus, Alaria esculenta, Palmaria palmata and Halidrys siliquosa (McGrath, 1992). Adults show a seasonal migration on Laminaria hyperborea, migrating down to the stipe before the old blade tissue is discarded in spring to early summer. Larger individuals prefer the lower wave exposure of deeper water (Warburton 1976). Approximately one third of the population examined by Graham & Fretter (1947) were the laevis form. However, Kain & Svendsen (1969) did not find any specimens in Laminarian holdfasts in Norwegian populations and the laevis form may be absent in Norway.

Substratum preferences	Algae	Physiographic preferences	Open coast Strait / sound Sealoch
Biological zone	Lower Eulittoral Sublittoral Fringe Upper Infralittoral	Wave exposure	Exposed Moderately Exposed
Tidal stream strength/Water flow	Moderately Strong (1-3 kn)	Salinity	Full (30-40 psu)
Habitat Preferences Additional Information	None
Distribution References	Hayward & Ryland, 1995b, Fretter & Graham, 1976, Graham & Fretter, 1947, McGrath, 1992, Warburton, 1976, Ebling et al., 1948, Seaward, 1990, Seaward, 1982, Kain & Svendsen, 1969, Vahl, 1971, MBA, 1957,