Jellyfish invasion as groundbreaking research determines cause

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 have been posted and bathers are warned not to enter the water.

“Why do they appear at this particular part of the lunar cycle? Where do these box jellyfish come from and where are they for the rest of the lunar cycle? Why has it become a monthly problem in just the last 30 years? These are the questions the latest study addresses.

Researchers at UH Manoa today released a 10-year study of Hawaiian box jellyfish.

The box jellyfish study determined that “a key number of hours of darkness during the lunar cycle” is what drives jellyfish to swim to shore.

UH said “this work is very important to the state in terms of planning and tourism as well as improving signage, public education and dissemination of evidence-based jellyfish sting care.” . Having had our share of jellyfish stings, we agree.

The School of Ocean and Earth Science and Technology (SOEST) at the University of Hawaii, in conjunction with the John A. Burns School of Medicine, has been studying local box jellyfish for more than two decades. . While scientists have used the approximation of 8–10 days after a full moon as the time when south-facing Hawaiian coasts are likely to see jellyfish, there has been a lack of scientific research.

Groundbreaking study of Hawaiian box jellyfish.

The researchers stated that “we have found that the dangerous monthly occurrence of the Hawaiian box jellyfish coastline correlates with specific nights of the lunar month – called Kaloa in the Hawaiian calendar – with a critical number of hours of darkness after sunset and before moonrise. .”

Reproduction is the key to the aggregation of jellyfish on the shoreline.

Researchers say that beach jellies are actively reproducing. In other words, “they were near the shore to reproduce”.

Fascinating indications were that “the period of the lunar cycle with a key number of hours of darkness or ‘absence of light’ causes mature animals to specifically swim to shore to spawn… Their speed and power of swimming were impressive!”

The study focused on jellyfish on Oahu, although most of the findings apply to those found on other islands, such as Kauai, where there was an outbreak this week. On Oahu, researchers now believe that jellyfish largely live on the lee side of Diamond Head, which provides food and shelter.

Only species of Hawaiian box jellyfish exhibit this specific behavior.

The study found that although there are more than 40 species of jellyfish in the world, it is “the only species that exhibits this mechanical lunar spawning migration behavior”. The same jellyfish we find in Hawaii are also seen in Saipan, Puerto Rico and Key West.

More studies are forthcoming, including efforts to help predict and inform about jellyfish, which are becoming a growing concern for those swimming and even beach walking on south-facing shores.

See Hawaii’s Jellyfish Sting Warnings | Important dates for your 2022 vacation.

Have you been stung by jellyfish in Hawaii?

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