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Japanese Kelp

Image Credit: GBNNSS

Status: Established

Habitat: Marine  

Threat: Habitat alteration


  • golden brown with a lighter-coloured stem
  • very wavy margins on the stipe, or stem, giving it a ridged appearance.
  • branched holdfast, or root
  • broad, flattened blade with a distinct midrib and wavy margins.


  • forms a dense ‘forest’ which blocks light and outcompetes native species
  • due to its rapid annual growth, can colonise areas where native seaweeds would not usually survive.


  • infestations can foul shellfish beds and cages, and slow shellfish growth by restricting the flow of water into cages
  • most likely to affect sheltered locations, harbours and pontoons and may become a major harbour pest.


Following the Government’s advice in relation to COVID-19, Loughs Agency has put in place a number of measures to maximise our capacity to continue to deliver our services as best we can.