Common Starfish

  • Scientific name: Asterias rubens
  • Also known as: Sea Star
  • Size: Usually up to 10cm across, although rare specimens can be larger.
  • Distribution: Very common around all of the British Isles.

The common starfish is made up of five arms and is usually yellowish to orange on the upperside and paler underneath, although some specimens can be purplish. The whole of the underside of the common starfish is covered in small, blunt, bumpy tubes which the starfish can use for moving and holding food. The common starfish usually grows to around 10cm across, although exceptional specimens can sometimes be found which are around 25cm across. The common starfish is found all around the UK in the intertidal zone on shingle and mixed ground beaches where there is some rock cover present, and can also be present in deeper water. Sometimes wind and tide conditions can lead to masses of common starfish being washed up onto beaches. The starfish can only move slowly and if stranded out of the water with no seaweed or rock cover the common starfish will die within a few hours.

Seagull eating starfish
A young European herring gull eating a starfish.

Being slow-moving and blind the starfish is no hunter and is instead a scavenger which feeds on anything it can find but shellfish that make up the majority of the starfish’s diet. The starfish can use its arms to pull whelks and cockles off the rocks they are clinging to, or pull open the shells of mussels. It then holds the shellfish within its five arms turns its stomach inside out through its mouth and into the shell of its prey. The starfish can then absorb the flesh of the prey and then suck its stomach back inside its body. Starfish are inedible, useless as bait and have zero commercial value. In areas where they are expanding in numbers, there are fears over the impact they could have on shellfish beds. Starfish are a source of prey for a range of other species including marine birds and some fish species.