The Two Species
It’s generally accepted that there are two species of manta rays that are frequently encountered by divers – the reef manta (Manta alfredi), and the oceanic manta (Manta birostris). So, if you’re lucky enough to see a manta in a dive, how can you tell which of the two species it belongs to?
Well size is the first distinguishing feature – with reef mantas being smaller, reaching up to 5.5m (18 ft), and oceanic mantas 7m (23 ft). But this is not really a reliable measure, as demonstrated by a recent dive trip to the Maldives, where there reef mantas were huge and easily on par with the size of oceanics in Socorro! So how else can we tell the difference?
I’ve learnt that the best to tell is by their markings. So if you’re above the manta, looking at the dorsal side, or top of the manta – if the shoulder markings form a sharp well defined T, it’s probably an oceanic manta. If the shoulder markings are less well defined, it’s probably a reef manta.
Now, if you’re below the manta, looking up at the ventral, or belly side, oceanic mantas will usually have a clear dark V shape along the pectoral fins, which won’t be there on a reef manta.