BIOTIC

BIOTIC Species Information for Asterias rubens
All Taxonomy Biology Distribution Reproduction

Researched by	Georgina Budd	Data supplied by	MarLIN
Refereed by	Prof. David Nichols
Distribution and Habitat
Distribution in Britain & Ireland	Found on all British and Irish coasts, especially amongst beds of mussels and barnacles.
Global distribution	Abundant throughout the north-east Atlantic, from Arctic Norway, along Atlantic coasts to Senegal, and only found occasionally in the Mediterranean (Mortensen, 1927)
Biogeographic range	Not researched	Depth range	Intertidal to depths of 650 m.
Migratory	Non-migratory / Resident
Distribution Additional Information	Aggregation of starfish In shallow coastal waters Asterias rubens sometimes occurs in dense aggregations of up to 100 specimens per m² (Table VII, Sloan, 1980). Dare (1982) reported an aggregation of Asterias rubens in Morecambe Bay, UK. The aggregation occupied 2.5 ha (1600 x 15 m) at its peak and contained at least 2.4 x10⁶ starfish of 6 cm mean arm radius. Feeding concentrations within the aggregation commonly attained 300-400 starfish per m² representing a wet weight biomass of approximately 12-16 kg m². It was estimated that the aggregation cleared a zone that contained 3500-4000 tonnes of Mytilus edulis within 3 months (June-August). Factors causing the aggregations of Asterias rubens are unclear but suggestions have been made that calm weather, amenable temperature and feeding conditions act together to give rise occasionally to aggregations. The occurrence of the phenomenon is dependent upon a large population of Asterias rubens larvae prior to the aggregation, which itself would be a function of good larval recruitment and growth conditions. Thus the irregularity of aggregations of Asterias rubens may be due to the need of a complex set of environmental variables to occur in the correct sequence over a number of seasons before an aggregation can occur. In addition, concurrent good mussel recruitment may also be required because an abundant prey source is a necessary focal point for the starfish (Sloan, 1980).

Substratum preferences	Gravel / shingle Coarse clean sand Bedrock	Physiographic preferences	Open coast Offshore seabed Strait / sound Enclosed coast / Embayment
Biological zone	Lower Eulittoral Sublittoral Fringe Upper Infralittoral Lower Infralittoral Upper Circalittoral Lower Circalittoral Circalittoral Offshore	Wave exposure	Exposed Moderately Exposed Sheltered Very Sheltered
Tidal stream strength/Water flow	Strong (3-6 kn) Moderately Strong (1-3 kn)	Salinity	Full (30-40 psu) Variable (18-40 psu)
Habitat Preferences Additional Information
Distribution References	Hayward & Ryland, 1995b, Fish & Fish, 1996, Hayward et al., 1996, Mortensen, 1927, Sloan, 1980, Vevers, 1949, Anger et al., 1977, Dare, 1982 (b),