A NSW Government website

Japanese seaweed / Wakame


Japanese seaweed (or wakame) is a highly invasive seaweed that can grow to 3m in length and has green-brown fronds. It grows in sheltered temperate waters, forming dense forests at depths of up to 15m and can quickly displace native habitats.



Japanese seaweed

Undaria pinnatifida

Key features:

  • Can grow up to 1-3m tall
  • Green-brown fonds
  • Leaves stop short of base
  • Frilly base
  • Hold fast
  • Midrib up to 3cm wide

Known locations:

  • Tas and Vic
  • Not known to occur in NSW


  • Can be highly invasive and grow rapidly into dense beds
  • Overgrows and excludes native algal species

Similar native species

These native species may be confused with this marine pest.


Cray weed/Strap weed
Phyllospora comosa

Key features:

  • No midrib or base
  • Long strand-like fronds with sawtooth edge, air sacks for floats
  • Up to 3m tall


  • Exposed rocky reef up to 20m depth


Common kelp
Ecklonia radiata

Key features:

  • No midrib or base
  • Often has spines, brown fronds, up to 2m tall
  • Appearance varies with depth (longer, smoother fronds in deep water)


  • Moderately exposed rocky reefs up to 44m depth


Bull kelp
Durvillaea potatorum

Key features:

  • No midrib or base
  • Large bulky fronds
  • Up to 8m tall


  • Exposed rocky reef up to 30m depth

How can you help?

Learn to recognise, and be aware of, the Japanese seaweed (or wakame) so that you can report any suspected new sighting.

If you see this pest in NSW, please report it immediately

  • Note the exact location
  • If possible take a photo and/or collect a sample
  • Freeze sample in a plastic bag
  • Report your sighting