Daring divers play tag with giant sharks

A whale shark, pictured by Oliver Roux. Published under Creative Commons licence

A whale shark, pictured by Oliver Roux. Published under Creative Commons licence

It takes a brave person to attach an electronic gizmo to a shark that’s as long as a bus. Two brave people, in St Helena’s case.

But the presence of whale sharks off the island has got scientists excited, and so it fell to Jeremy Clingham and Anthony Thomas to try to tag a couple.

Whale sharks feed on plankton, not people, but even so, the two females chosen were each at least ten metres long, with very big mouths. It was a daunting job.

But Jeremy and Anthony succeeded, and made scientific history for St Helena.

The MK10 tag fitted to one of the whale sharks. Picture: Steve Brown

The MK10 tag fitted to one of the whale sharks. Picture: Steve Brown

Thanks to their efforts, marine biologists can now add to the little that is known about the wanderings the creatures make through the world’s oceans.

According to a note from St Helena’s marine conservation unit, their presence in St Helena waters has long been taken for granted.

“They show up every November and disappear April/June. It really wasn’t until last year that it became apparent that a number of the females seen during a large gathering of whale sharks appeared to be pregnant.”

Anecdotal evidence and local records were compared with theories by researchers around the world, and it was realised that the presence of the leviathans “could be more interesting” than anyone had realised.

In October 2013, Elizabeth Clingham travelled to Atlanta, in America, to present a paper at the third international whale shark conference.

She returned with the two satellite tags, provided by the Mote Marine Laboratory and the Georgia Atlanta Aquarium – along with training in how to deploy them.

Click the pic to see a bigger version of Steve Brown's image

Click the pic to see a bigger version of Steve Brown’s image

A single whale shark was spotted off St Helena on 30 November 2013, and by early January, there were thought to be 18 of them in island waters.

“On Saturday, 4 January 2014,” says the conservation department, “two suspected pregnant females were sighted.

“Under the instruction of the marine section, just outside of Thompsons Valley Island Jeremy Clingham and Anthony Thomas bravely stepped up to the challenge of inserting the tags into the large 10-metre-plus female whale sharks.

“The two tags were successfully deployed.

“Steve Brown was in charge of the camera and ensured that pictures of the whale sharks were taken of their left flanks, above the pectoral fin, to allow for photo identification.”

The first tag is a transmitter on a long tether. When the whale shark surfaces, the transmitter floats up and communicates directly with the Argos satellite, tracking the whale shark’s movement.

The second tag – called an MK10 – is attached to the creature itself. “It will collect data on the depths that the animal is swimming at, temperature, light levels, etc.

“This data is collected and stored in the memory of the tag.  In this case the tag has been programmed to collect data for 150 days.  On the 150th day the tag will detach itself from the animal and float to the water surface, where it transmits the data to the satellite.

“This tagging is the first ever for St Helena and a huge achievement.”

READ MORE:
Whale sharks – Wikipedia
MK10 pop-up tag

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