Prickly Seaweed

Prickly Seaweed (Acanthophora spicifera)

Acanthophora spicifera

Photo courtesy of DAR


  • Smooth cylindrical branches (CABI, 2019)
  • Can be light pink, brown, green or yellow in color (CABI, 2019)
  • Usually dark in color in intertidal areas and lighter in color in low water motion areas (GISD, 2021)


  • Typically found on small reef flats, in tidepools, and in the intertidal zone of benches (GISD, 2021)
  • Generally attaches to hard substrates (UH Botany Dept., 2001)
Acanthophora spicifera

Photo courtesy of DAR

Impacts & Concern:

  • Reproduces asexually through fragmentation, which leads to widespread distribution (UH Botany Dept., 2001)
  • Often grows next to and competes with native species (UH Botany Dept., 2001) 
  • Most abundant seaweed on shallow reefs, most widespread invasive algae in Hawai‘i (HEAR, 2017)


  • Unintentionally introduced from Guam through hull fouling in 1950 (HEAR, 2017)
  • First fragments were discovered in Pearl Harbor in 1952 (HEAR, 2017)

Distribution in Hawaii (UH Botany Dept., 2001)

  • Kauai: Present 
  • O‘ahu: Present
  • Molokai: Present
  • Lanai: Present
  • Maui: Present
  • Big Island: Present

Related AIS Team Management Projects:

  • Urchin outplanting efforts in Kāne‘ohe Bay and Waikīkī MLCD/FMA


  • UH Botany Department. (2001). Acanthophora spicifera. Marine Algae of Hawaiʻi.
  • Global Invasive Species Database (GISD). (2021). Species profile: Acanthophora spicifera. on 22-03-2021.
  • CABI Invasive Species Compendium. (2019). Acanthophora Spicifera. [Data sheet].
  • Hawaii Ecosystems at Risk Project (HEAR). (2017). Acanthophora spicifera (Rhodomelaceae).