Serrated wrack

Serrated wrack

Serrated wrack ©Gemma de Gouveia

Serrated wrack

Scientific name: Fucus serratus
This brown seaweed lives in the lower shore and gets its name from the serrated edges to its fronds.

Species information


Length: up to 70cm

Conservation status


When to see

January to December


Serrated wrack or Toothed wrack is a common wrack seaweed that grows just above the low water mark on rocky shores. Its name comes from the serrated edges on its fronds. These edges are so serrated that some people even call this seaweed Saw Wrack. Serrated Wrack provides shelter for many creatures in the lower shores, including Flat periwinkles and many small crustaceans. Other seaweeds are found to grow on its fronds, including Dulse. The dense bunches provide shade and shelter in rockpools too - lift up a bunch and see what's hiding underneath (though make sure you put everything back where you found it!).

How to identify

An olive-brown brown 'wrack' seaweed, recognised by the strap-like branching fronds with jagged serrated edges.It does not have air bladders and the fronds are flat not spiraled.


Common on rocky shores all around our coasts.

Did you know?

Reproduction in Serrated wrack peaks in late summer when gametes are released into the water to be fertilised externally. Female Serrated wracks can release more than a million eggs. These eggs produce a pheromone called Fucoserratin that acts as a sperm attractant!

How people can help

Serrated 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.