A box jellyfish advisory remains in effect today for Waikiki Beach, Ala Moana Beach and Maili Beach, Oahu, and at Poipu Beach and Salt Pond Beach, Kauai, as they were widely seen on south facing beaches. Warning signs were posted and beachgoers are being warned to not go into the water.
“Why are they appearing at this particular part of the lunar cycle? Where do these box jellyfish come from and where are they found the rest of the lunar cycle? Why has this become a monthly problem in only the last 30 years?” These are the issues that the latest study addresses.
Researchers at UH Manoa today released a 10 year study on Hawaiian box jellyfish.
The box jellyfish study determined that “a key number of hours of darkness during the lunar cycle” is what triggers jellyfish to swim to shore.
UH said that “this work is very important to the state in terms of planning and tourism as well as improved signage, public awareness and dissemination of evidence-based jellyfish sting care.” Having had our share of jellyfish stings, we concur.
University of Hawaii’s School of Ocean and Earth Science and Technology (SOEST) together with the John A. Burns School of Medicine, have now studied local box jellyfish for over two decades. While scientists have used the approximation of 8–10 days following a full moon as the time when south-facing Hawaii shores are likely to see jellyfish, there’s been a lack of scientific research.
Groundbreaking Hawaiian box jellyfish study.
Researchers said that “We found that the dangerous monthly shoreline appearance of the Hawaiian box jellyfish, correlates with the specific nights of the lunar month—referred to as Kaloa in the Hawaiian calendar—with a critical number of hours of darkness after sunset and before moonrise.”
Reproduction is key to shoreline aggregation of jellyfish.
Researchers say that the jellies at the beach are actively spawning. In other words, “they were nearshore to reproduce.”
Fascinating indications were that “the period of the lunar cycle with a key number of hours of darkness or the ‘absence of light’ cues mature animals to specifically swim to the shore line to spawn… Their swimming speed and power was impressive!”
The study focused on jellyfish on Oahu, although much of the findings apply those found on the other islands, such as Kauai, were there was an outbreak this week. On Oahu, researchers now believe that jellyfish largely live on the leeward side of Diamond Head, which provides food and shelter.
Only Hawaiian box jellyfish species exhibit this specific behavior.
The study found that even though there are over 40 species of jellyfish globally, this “is the only species that exhibits this clockwork lunar spawning migration behavior.” The same box jellyfish we find in Hawaii are also seen in Saipan, Puerto Rico, and Key West.
Further studies lie ahead, including efforts to help predict and inform regarding jellyfish, which are becoming increasingly concerning for those swimming and even walking on the beach on south facing shores.