A Milky Way In The Ala Wai Canal

Ron Mizutani
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Wednesday - March 04, 2009
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Thousands of moon jellyfish invaded the Ala Wai Canal recently

Chuck Baum has scanned the Ala Wai Canal from his Ala Moana apartment hundreds of times over the years. But in 23 years, he has never seen anything quite like what he saw recently.

“It was like the Milky Way down the middle of the Ala Wai,” says an excited Baum. “We’re talking thousands, not hundreds. I was amazed!”

What Baum was looking at was not a spiral galaxy but an enormous amount of moon jellyfish. The slow-moving translucent creatures are often mistaken for our monthly visitors the box jellyfish.

“The moon jellyfish, or Aurelia aurita, is endemic to the Ala Wai Canal and other boat harbors around Oahu,” says University of Hawaii researcher Angel Yanagihara. “Moon jellies prefer still water as their habitat. In fact, they don’t do well in the ocean, around coral reefs or wherever there is wave action.”

Moon jellyfish are often called saucer jellyfish. They live in brackish water with low salt content and are usually about 8-15 inches across. They can be recognized by their four gonads seen through the top of the bell, and unlike box jellies, these critters do not pack a punch.

“Although jellies are venomous, not all are capable of penetrating human flesh,” says Yanagihara, who has studied box jellyfish in Hawaii for 12 years. “Moon jellies sting, and they do capture their prey, but they don’t need a sophisticated piercing sting to protect themselves. As a result, you can’t feel the sting. Its venom just washes right off.”

That is welcomed news to Baum.

“With all the talk of box jellyfish and having been stung by one and a Portuguese man of war, knowing these don’t sting is comforting,” says a relieved Baum. “When I saw them I said, ‘wow, they’re beautiful,’ but there were just so many of them.”

Baum says he’s seen moon jellies scattered in areas around the canal and parts of Ala Wai Yacht Harbor before, but never in these large numbers.

“You can’t really get a sense of how many are out there unless you’re looking down from above,” says Baum. “Everyone who walked past the bridge (on Ala Moana Boulevard) walked right by them.”

Yanigahara says this particular species goes through population fluxes.

“Its population changes depending on rainwater and various forms of nutrition in the water,” she explains. “When plankton density increases or algae bloom, their population goes up. They wax and wane based on the plankton they feed on.”

The increase in moon jellies coincidentally comes at a time when Yanagihara and her research group have noticed an increase in box jellies. Ironically, the monthly visitor wreaks havoc on beachgoers seven to 10 days after a full moon. While moon jellies live in still water, box jellies live off-shore and swim to shore in massive numbers during the night to spawn.

“The numbers are actually going up again,” says Yanigihara of the last four influxes since November. “This year is stacking up to be another busy year, and the numbers are off the charts again. We could actually surpass 2001 when we saw nearly 10,000 box jellies.”

Baum says his discovery in the Ala Wai has given him a different outlook on all jellies, which he says, “move with amazing grace.” He realizes they are creatures of the ocean that oftentimes get a bad rap.

“We see them in the news and hear about their stings, but they are actually beautiful to watch,” he continues. “To see them in such large numbers was just phenomenal.”

Phenomenal, perhaps even out of this world - and why not? After all, it was a Milky Way in the Ala Wai.

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