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Questions and answers help spread knowledge


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POSTED: Monday, July 13, 2009

A reader, Cynthia, e-mailed me this question: “;Today my husband was cleaning the bottom of our boat, docked in front of our townhouse in Kuapa Isle, Hawaii Kai. When he came out of the water, he was covered with little worms. I saw hundreds of the critters, about the size of a grain of rice and smaller. They bit him and stuck to him. ... Any ideas as to what they are? It's very creepy!”;

No, I don't have any idea what those black, bitey, wormy things might be, but I'd like to. Cynthia wrote back later that someone told her they were shrimp larvae, but when she called the Oceanic Institute, she was told that shrimp larvae aren't black.

“;The mystery continues,”; she wrote.

If anyone can enlighten us, please do.

Another e-mail arrived from a National Oceanic and Atmospheric Administration worker with a clarification of my recent GPS column. “;The GPS is not off by two miles, the Mexican charts have an offset. ... The GPS, for its part, is accurate.”;

I stand corrected. GPS readings are indeed accurate. But a satellite saying “;you are here”; is only as good as the map it's pointing to.

GPS satellites send the longitude and latitude of a device via antenna, marking the exact location on the map or chart displayed on the GPS screen. If the chart was drawn wrong, it looks like the GPS is wrong.

In any case, where the charts are wrong (as in Palmyra, the Society Islands, Mexico and others), you can't rely on your GPS. The catch is that you have to know the charts are wrong.

My NOAA reader had an experience similar to my encounter with fog in the Sea of Cortez: “;Some of the soundings in the northern part are from the 1870s,”; he wrote. “;I recently led a research expedition there and it was a navigational nightmare.”;

While I was in Mexico sailing around uncharted rocks, a reader, Sue, from Kailua, e-mailed me a concern. “;When walking on Kailua Beach on May 23 or May 25, I discovered a little box jellyfish on the sand at the water's edge. ... I had never heard of the box jellies being on Kailua Beach. I hope this isn't the first of many! This wasn't the normal 10 days after the full moon as is customary for the south shore. What is happening?”;

This box jellyfish species is known around the world, being found in the tropical waters of the Atlantic, Pacific and Indian oceans. It may or may not be native to all these places (ships' ballast help such organisms get around), but how ever it got to our islands, we're stuck with it.

A 1977 Bishop Museum publication reports, “;Nearly all collected specimens (of box jellyfish) have been found near the surface at various locations around the Hawaiian Islands.”;

The report doesn't say near which islands they found their specimens, but it implies box jellyfish were widespread. (In 2004, I found five on a Tern Island beach in remote French Frigate Shoals.)

Their numbers were probably small then. I'm guessing this because the report recounts swarms of these jellyfish appearing suddenly on Waikiki Beach in June 1951, as if this was odd. That influx eventually became the predictable, monthly pattern we Oahu residents have learned to live with on our South Shore.

So to answer Sue's question, what's happening in Kailua waters is (hopefully) normal.

Thanks, all, for sharing your knowledge and experiences. When you share with me, you share with many.

 

Susan Scott can be reached at www.susanscott.net.