Description: Distinctive, growing from a minute discoid holdfast to 8 m long and 2 - 3 mm thick. Cylindrical, hollow of uniform diameter, cord-like and unbranched. The plants are very tough and slimy with a covered with fine deciduous filaments when young.

Habitat: Epilithic. Commonly abundant at the low littoral and upper sublittoral to 10 fathoms. Most abundant in sheltered sites.

Distribution: Generally found on all shores of the British Isles and the Channel Isles. Europe: Mediterranean, Portugal, Spain, France, Belgium, Netherlands, Germany, Denmark, Baltic Sea, Norway, Sweden, Finland, Faroes, Jan Mayen and Bjornoya, Iceland and Spitzbergen. Greenland. Atlantic coast of North America: Canada, Maine, New Hampshire, Massachusetts, Rhode Island, Connecticut, Long Island and New Jersey. Further afield: Canary Islands, Spitzbergen, the Murman Sea, the White Sea, American Arctic Sea and Baffin Bay on the west coast of Greenland, north-east Pacific from Bearing Sea, Alaska, China and Japan.

Similar Species: Himanthalia elongata. Chorda, however, is unbranched and does not grow from a mushroom-shaped base. Young Scytosiphon lomentaria and Halosiphon tomentosus may appear similar.

Key Identification Features:

• Long, slimy, unbranched but tough.

Distribution Map from NBN: Chorda filum at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Chorda filum at iNaturalist World Species Observations database.

WoRMS: Chorda filum at World Register of Marine Species.