It's fake.
Awhile back, when that first surfaced, the Aquarium I was working at made a big deal of it and even had in on their website (Education dept kicked it out prior to checking with any of the animal staff). We asked them to take it down ASAP (as it made the Aquarium look like idiots). The photo has been messed with. We had a very large version of it some how, and when you zoomed in closely, you could see the pixalated areas that had been 'touched up' in a photoshop program.
I love how in the text she claims to have immediately returned the shark - even thought it's obviously due to the dermal abbrassions that this shark is both dead, and has been laying dry on it's stomach for quite some time.