Learn & Explore/Species/Introduced & Invasive/Hook Weed

Hook Weed

Category: Invasive

Fast-growing invasive seaweed with hooked branches that threatens native reefs.

Hook Weed (Hypnea musciformis)

  • Masses of intertwined branches, with the ends of the projections forming hooks 1

  • Usually a red color but can be yellow or brown in some environmental conditions 3

  • Can spread and reproduce through fragmentation, waves break off hooks which drift and attach to other locations 4

da9d608b8cabc04001893a6b9d49dec82e44632a

Habitat

  • Often found attached to rocks and reef algae in intertidal pools and beaches 1

  • Can be found free-floating in bloom stage 3

Impacts & Concern

  • Rapid growth rate and easy fragmentation 1

  • Ability to grow on other drifting seaweeds 1

  • Mats of seaweed wash up on beaches resulting in decreased beach use and property values 4

  • Competes with and overpowers local native algae and corals 2

0542aa2be58d3783fce57e8dcd67fb413deea1cb
Photo Credit: [To Be added]

Introduction

  • Illegally introduced to Kāne‘ohe Bay from Florida in 1974 3

  • Intended for commercial aquaculture use 3

Distribution in Hawai’i

  • Kauaʻi: Found at Prince Kuhio Beach and Salt Pond Beach

  • O‘ahu: Large amounts from Kahala to Makaha

  • Molokaʻi: Found in some areas including Kaunakakai and Kupepe

  • Lānaʻi: Not documented

  • Maui: Large amounts on windward and leeward reefs

  • Hawaiʻi Island: Not documented

0731f31753ed275b128e2f934df0689bb1d636b9

References

1. Eyes of the Reef (EOR). (2015). Hookweed (hypnea musciformis). Eyes of the Reef Hawaiʻi. https://eorhawaii.org/education/marine-invasive-species/hypnea-musciformis/

2. CABI Invasive Species Compendium. (2019). Hypnea Musciformis. [Data sheet]. https://www.cabi.org/isc/datasheet/107763

3. UH Botany Department. (2001). Hypnea Musciformis. Marine Algae of Hawaiʻi. https://www.hawaii.edu/reefalgae/invasive_algae/rhodo/hypnea_musciformis.htm

4. Hawaii Invasive Species Council (HISC). (2017). Hookweed (Hypnea musciformis). https://dlnr.hawaii.gov/hisc/info/invasive-species-profiles/hookweed/

  1.  

Other Introduced & Invasive

a4d0af7b6652b487e5c303e920d4ccc987d7baf9

Marine

40c921b134b22783f181226c106c8338e2bdadd2

Freshwater

c8eb3b434663062e9fa4847935a341d6c8967322

Brackish

a9568c59478797b5a3a43af86ec96d04950dc31f

Seaweed/Algae