Monday, July 04, 2011

GW in Tunisia!

This GW was apparently caught in Tunisia.

How did these creatures get there?

Very possibly, by swimming there from Oz!
They got there because a few pregnant females got lost around the Cape of Good Hope some 450,000 years ago and ended up in the Atlantic Ocean, according to scientists from Aberdeen University. This is a beautiful hypothesis and a fantastic paper and everybody should read it!
Talk about an epic going walkabout!

Or, as the Abstract states
Antipodean white sharks on a Mediterranean walkabout?
Historical dispersal leads to genetic discont
inuity and an endangered anomalous population

Chrysoula Gubili, Raşit Bilgin, Evrim Kalkan, S. Ünsal Karhan, Catherine S.Jones, David W. Sims, Hakan Kabasakal, Andrew P. Martin and Leslie R. Noble

The provenance of white sharks (Carcharodon carcharias) in the Mediterranean is both a conundrum and an important conservation issue.
Considering this species's propensity for natal philopatry, any evidence that the Mediterranean stock has little or no contemporary immigration from the Atlantic would suggest that it is extraordinarily vulnerable. To address this issue we sequenced the mitochondrial control region of four rare Mediterranean white sharks. Unexpectedly, the juvenile sequences were identical although collected at different locations and times, showing little genetic differentiation from Indo-Pacific lineages, but strong separation from geographically closer Atlantic/western Indian Ocean haplotypes.

Historical long-distance dispersal (probably a consequence of navigational error during past climatic oscillations) and potential founder effects are invoked to explain the anomalous relationships of this isolated 'sink' population, highlighting the present vulnerability of its nursery ground
The GWs in the Med are probably rare and severely depleted.
I've known about them ever since one killed the Italian dive pioneer Maurizio Sarra in 1962, a fact that is being remembered by Italy's prestigious underwater photography prize. They are regularly sighted off Sicily and have been caught everywhere including Mallorca as per David's brand new documentary Behind Blue Glass - and buddy don't u dare come here without my copy!

And then, there is Malta.
There, the Great White is protected thanks to our friend the indefatigable Sharkman, it is there that the largest ever GW was thought to have been caught (since debunked) and it is from there where we're being regularly entertained with fishy tales of attacks and further catches.

Thing is, we know next to nothing.
From what I understand, everybody knows there's GWs but nobody seems to be studying, let alone tracking them. Maybe this may be a fertile new ground for somebody of the caliber of Domeier instead of wasting energy on combating the territorial Californians?
Just a suggestion! :)

BTW Junior is doing just fine.
The latest ping shows him migrating normally and he's due to track back shortly - and I must say, I'm very much looking forward to the comments, and the images (!) by Domeier's abuse spouting detractors when he shows back at the Farallones!

Junior tracks: 2009/2010 offshore migration in yellow and the 2010/2011 offshore migration in red

1 comment:

OfficetoOcean said...

Ooh one of my very, very favourite sharky subjects!! The Med's history with the White Shark is pretty amazing, more so that it's relatively unknown outside of the specialist European Shark community and local fishermen.

Ian Fergusson has been doing brilliant work for years in regards to GW in the Med as has my good friend Gabriel Morey, they are actually in the process of trying to gather data and ideally tag at least one GW at the moment, focussing around the Balearic islands... Favignana (apologies if spelled wrong)off the coast of Sicily is one of the only places in the world where a baby GW hs been spotted in the same georgraphic location as an adult female within the same time frame...

I have a few theories about the Med and its GW which I will undoubtedly bore you with next week! :D Fear not, I am actually burning you a DVD as I type this and I'd like to think you'll find some of my film interesting!

This GW in the picture, I was actually discussing this with Gabriel whilst in Mallorca, it was 2009 it was caught and as is the case with most Med Whites, was found in the Tuna nets although they could have let it go as it was alive when discovered which is quite unusual. Apparently, the captains of cruise ships occassionally see them swimming at the surface between Ibiza and Nice on the crossings there. I could go on forever about this but I don't wanna ruin the film for you :D