Upside-Down Jellyfish

Upside-Down Jellyfish (Cassiopea andromeda)

upside down jellyfish

Photo Courtesy of DAR


  • Yellow with white and pale spots (EOR, 2015)
  • Brown frilly tentacles (EOR, 2015)
  • Can grow up to 30 centimeters in diameter (Bishop Museum, 2001)
  • Often mistaken for sea anemones (Eldredge & Smith, 2001)


  • Lies upside down on sandy bottoms (EOR, 2015)
  • Found in calm, shallow water such as lagoons and intertidal flats (EOR, 2015)

Impacts & Concern:

  • Have a mild sting (Eldredge and Smith, 2001)
  • Ecological impacts have not been studied (Eldredge & Smith, 2001)


  • Came from the Philippines to Pearl Harbor between 1941 and 1945 (Eldredge & Smith, 2001)
  • Spread by hull fouling or in the ballast water of ships (EOR, 2015)

Distribution in Hawaii:

  • Kauai: Not documented
  • O‘ahu: Kāne‘ohe Bay, Ala Wai Canal, Honolulu Harbor (Eldredge & Smith, 2001)
  • Molokai: Kaunakakai (Eldredge & Smith, 2001)
  • Lanai: Not documented
  • Maui: Not documented
  • Big Island: Waikoloa fish ponds (Eldredge & Smith, 2001)


  • Eldredge, L. G., & Smith, C. M. (2001). A guidebook of introduced marine species in Hawaii. Honolulu: Bishop Museum and the Univ. of Hawai’i
  • Eyes of the Reef (EOR). (2015). Alien invasive invertebrates- Upside down jellyfish. Eyes of the Reef Hawaiʻi.
  • Bishop Museum. (2001). Cassiopea andromeda. Introduced marine species of Hawaii Guidebook.