Egg wrack

Egg wrack

Egg wrack ©Nigel Phillips

Egg wrack

Scientific name: Ascophyllum nodosum
This yellow-brown seaweed grows in dense masses on the mid shore of sheltered rocky shores. It is identifiable by the egg-shaped air bladders that give it its name.

Species information


Length: up to 2m

Conservation status


When to see

January to December


Egg wrack is a common wrack seaweed which grows on sheltered rocky shores, around the mid shore zone. It has long, leathery strap-like fronds with egg-shaped air bladders along the lengths. Egg wrack is a long-lived species, with individuals growing slowly for decades. They do not cope well on exposed shores (those with strong wave action), but they flourish on very sheltered shores to the extent of dominating these environments. The dense masses of Egg wrack provide shelter for many species on rocky shores - lift the fronds out of the way and see what is hiding underneath (but make sure you put them back again afterwards!).

How to identify

Egg wrack has long, yellow-brown, strap-like fronds with air bladders protruding at regular intervals along their length.


Common on sheltered rocky shores all around our coasts.

Did you know?

Egg wrack, also known as Knotted Wrack, often bears tufts of a small, reddish epiphytic (plants that live on other plants) algae, Polysiphonia lanosa. This filamentous 'Red Seaweed' forms pom-pom-like structures on the Egg wrack.

How people can help

Egg wrack and other species of seaweed provide food and shelter for all kinds of shore creatures from grazing molluscs to tiny fish. When rockpooling, be careful to leave everything as you found it - replace any seaweed you move out of the way, put back any crabs or fish and ensure not to scrape anything off its rocky home. If you want to learn more about our rockpool life, Wildlife Trusts around the UK run rockpool safaris and offer Shoresearch training - teaching you to survey your local rocky shore. The data collected is then used to protect our coasts and seas through better management or through the designation of Marine Protected Areas. The Wildlife Trusts are working with sea users, scientists, politicians and local people towards a vision of 'Living Seas', where marine wildlife thrives. Do your bit for our Living Seas by supporting your local Wildlife Trust or checking out our Action Pages.