First of all VERY nice picture, wish I could have stayed longer to have watched this, but as it was we had to plead more time to see the otters as it was
Secondly, the only species of stingray I saw listed on the ID boards in the tunnel were Southern stingray (Dasyatis americana), though looking at the pictures on Wikipedia they'll have to be a variable species for it to all add up. I could possibly have missed a board, but I remember me and AG discussing size difference and we concluded it was likely gender related rather than species related, as that was the only board we could see.
I found a couple of references to Dasyatis americana at Blue Planet, but that's not to say these are the same species. As you mentioned, the ID boards were lacking and I was too busy concentrating on the photography to soak up what the presenter was saying.
Secondly, the only species of stingray I saw listed on the ID boards in the tunnel were Southern stingray (Dasyatis americana), though looking at the pictures on Wikipedia they'll have to be a variable species for it to all add up.
It was just the wikipedia pictures, it didn't seem to quite match up somehow. I think it was just the size, but of course the picture could have been of a youngster or the opposite sex [males in stingrays are the smaller?].