Marine light show at Pak Nam Pran

[magobligin]

Last night as we sat on the concrete seaside promenade at Pak Nam Pran having a Thai picnic my wife pointed to flashing lights in the sea immediately offshore of the gambion rock works for the promenade. On investigation we found a shoal, possibly of cuttlefish, stretching over a distance of approximately 200 metres providing a marine light-show. They were displaying in water that could not have been deeper than around 30 centimetres and I was wondering if any amateur itchyologists in the forum could explain this behaviour; why would these creatures, if indeed they were cuttlefish, display like this and why we're they in such shallow waters?

I look forward to any explanations of this unusual phenomenon.

[buksida]

Are you sure it wasnt bioluminescence (though it isnt the season for it) or squid?

Cuttlefish are one of the most complex and mysterious of marine creatures, their communication signals are a mystery to scientists. It has recently been discovered that they use polarised light to communicate:
http://www.australiangeographic.com.au/ ... nicate.htm

[magobligin]

Definitely not bioluminescence as i have experienced that whilst wading in the sea just after sunset. We could identify individual creatures however the water was too silted to see them in any detail. I know cuttlefish have a very complex display capability but I was not aware that that squid were capable of this type of light display. Also it is our first sighting of this phenomenon despite many picnics at exactly the same spot at the same time in the early evening.

[PeteC]

Could it be this? http://en.wikipedia.org/wiki/Noctiluca_scintillans

I swam with those at night off Boracay in the Philippines back in 1989. Mind boggling experience. Following link are some stock photos from Google: https://www.google.com/search?q=glowing ... 80&bih=668

Pete

[magobligin]

The photographs are fantastic Pete, but unfortunately not helpful as my sighting was of individual creatures maybe as long as 20 centimetres in length or possibly more ....not a mass of microorganisms.

[migrant]

Here in southern California, about once a year, the squid will run as you describe. We were having dinner at a restaurant on the beach a few years ago and after, walked out on the pier where people were fishing. The fishermen were pulling up squid as quickly as they could get a line in the water. Talking to some of the long timers there they told us about the yearly run.

I didn't see the lights, but could it have been the moon reflecting?

[hhfarang]

I spent an entire one hour dive with a single cuttle fish and took up an entire roll of 35mm film on it. Indeed they are some of the most amazing animals in the sea. I will try to sort out the photos and post the scans later when I have time but it was one of the most rewarding dives of my life and I never moved more than ten meters.

[magobligin]

Look forward to seeing your photographs hhfarang. Migrant it was definitely not reflection of the moon on the sea, if you can imagine a creature about 20 centimetres long with an envelope of green coloured light surrounding it (green colour may be as a result of viewing through seawater). I estimate around 12-15 creatures in the grouping, they were not shoaling like fish but behaving as individuals.

Going to visit Pak Nam Pran tonight to see if they are still about.

[hhfarang]

Look forward to seeing your photographs hhfarang.

A view of the whole animal...

As I approached for close shots he/she flashed through a myriad of colors in rapid succession, a warning of some kind I suppose. Also, I noticed while swimming with it that it could hide very well by changing it's color to conform to the background. Two closer head shots...

[magobligin]

Superb photos hhfarang, reminds me just how complex and "intelligent" these creatures are. I always thought they preferred deep water and almost never allowed themselves to be trapped in shallow water. At what depth were your photographs taken?

[hhfarang]

Superb photos hhfarang

Thank you very much. I wish I were younger and still able to pursue that hobby with a housed digital camera. It was a real challenge with film as I went down with a 36 exposure roll of Kodachrome each dive in my Nikonos camera and usually didn't see the photos myself until several days after I returned home and got all the film developed.

At what depth were your photographs taken?

It was over two decades ago and my old brain is getting a bit fuzzy, but I think it was on a fairly shallow reef at 30 to 40 feet (or 10 to 12 meters).

[STEVE G]

I was reading on the net that there is such a thing as a comb jellyfish which exists off the coast of Thailand and also glows.

[buksida]

Saw four cuttlefish together, two mating pairs, on a recent dive in Indonesia - spectacular sight.

[magobligin]

I travelled to Pak Nam Pran earlier this evening and I had wanted to arrive at the tide turnaround period where the tide is neither flowing nor ebbing however due to a delay in leaving my home I arrived late at the the seashore and the tide was on the ebb. Needless to say there was no sign of the creatures I had gone to look for.

I guess it is the case where you are lucky if you just happen to be in the right spot at the right time when something unusual happens.