Orange cloak sea squirt (Botrylloides violaceus)
Native to Japan, this sea squirt forms firm gelatinous sheets or cushions up to 15 cm across and each colony has a single colour: bright orange, violet, brick red, pink or yellow. It is well established in harbours and marinas throughout the UK. It is present at high densities in some Plymouth marinas and is now regularly being found in local natural habitats. Colonies can overgrow other fauna and occupy substantial space. There is some evidence of displacement of native species. Back-to-back growth can produce fist-sized three-dimensional masses likely to render submerged gear cumbersome. Colonies can also block inlet pipes on boats. Where well established, mechanical clearance (and disposal) or blanket biocide treatment would be required to ensure eradication.
Environmental risk: MEDIUM
Economic risk: MEDIUM
Image: J. Bishop © MBA