Acorn Barnacle

Semibalanus balanoides


The commonest barnacle found around our shores, the Acorn Barnacle lives attached to any hard substrate, including rocks, the legs of piers, old boats and even other animals. They are filter feeders, picking plankton and detritus out of the water. Found around the low tide mark.

How to identify

One of several very similar species of barnacle, which can be hard to tell apart. The Acorn Barnacle is generally grey-white in colour, with a diamond-shaped opening.

Where to find it

Found all around our coasts.


When to find it

  • January
  • February
  • March
  • April
  • May
  • June
  • July
  • August
  • September
  • October
  • November
  • December

How can people help

Our seas and coastline are in need of protection if we are to keep our marine wildlife healthy. The Wildlife Trusts are working with fishermen, researchers, politicians and local people towards a vision of 'Living Seas', where marine wildlife thrives. This work has recently had a massive boost with the passing of the Marine Bill, promising sustainable development of the UK's marine environment. Do your bit for our Living Seas by supporting your local Wildlife Trust.

Species information

Common name
Acorn Barnacle
Latin name
Semibalanus balanoides
Barnacles, crabs, shrimps and lobster
Length of shell: 2cm Average lifespan: up to 18 months
Conservation status