The origin of whale shark spot pattern identification

Posted on November 20, 2008
Written by: Shark Savers

November 15, 2008

Is it raining yet?

Are you one of the courageous ones who chose to stand by until better weather, on our little rock? If so, well done. If not, can’t blame you. Boats have had a hard time getting out of the harbour to keep divers going out to play, so there has been only one encounter reported to us in the last month. Let’s hope for fairer skies and calmer seas in the one to come.

Sharks by numbers

Any guess on just how many Honduran whale sharks have been identified in the Ecocean Photo-ID Library?
Well you, good people of Utila, are the proud parents of 65 whale sharks at this point. Thanks to photos taken by snorkellers, dive masters, instructors and researchers. For 2009, we are going for the 3 digit mark.

In the beginning

On December 17, 2004 in a country not-so-far-away, H-001 was created (H for Honduras).
A female. She is our very first whale shark identified in the Ecocean Library. Since then she has been reported 16 times over a period of years, not only in our waters but also in Belize. Of all the encounters, only one confirmed her to be female.

The Hubble Telescope?

Whale Shark spots for identification
Whale Shark spots for identification

Astronomers devised a technique to match star patterns, but it works for whale sharks too. It’s all about white dots on a dark background. We need that little area behind the gills. We highlight each spots and it’s actually the angles between all those spots that we use. We triangulate. As the shark grows, the spots will move also but the angle between each spot doesn’t change.

If you or any of your divers get a photo of a whale shark, please do not hesitate to send it to

The dive centre and the photographer will be updated on weither it is a new shark or a returning one.


Thanks for playing,

Isabelle Foisy
Utila Whale Shark Research