Shark rays: are they sharks or are they rays?
Dr Blake Chapman
Dr Blake Chapman
LET ME INTRODUCE you to one of my old nemeses: the shark ray.
The first obvious fact for clarification is what exactly are these things? Are they sharks, or rays?
Here’s a hint: you may have also heard of these animals as bowmouth guitarfish. Although, that still doesn’t really give anything away.
They are, in fact, rays. However, like their close ‘rhino ray’ relatives – the wedgefish (also rays!) and giant shovelnose rays – they really do look more like sharks than rays.
Shark rays are large, growing to a maximum size of just over 2.5 m, and bulky. Plus, they have two large dorsal fins on their back, even larger pectoral fins behind their head and a shark-like caudal, or tail, fin with well-developed top and bottom lobes, all-up making them very un-ray-like.
However, shark rays have two large spiracles on the top of their heads, and nostrils, mouth and gills on the underside of their body; these are the clear giveaways that they are definitively rays.
Shark rays are really easy to identify, given their highly unique body shape.
Most characteristically, they have broad, rounded heads with blunt snouts. They are often a brown-grey colour, but sometimes take on a bluish tint. They are dotted with large white spots along their backs and fins, and dark bands between their eyes.
As they get older, though, their spots and colour patterning tend to fade. They are also adorned with large thorns that cover prominent ridges along their back.
These highly unusual and prehistoric looking animals have become a favourite of mine, since forming a very strong love-hate relationship with a couple of individuals that were kept at an aquarium I worked at.
I have fond memories of one of these animals insisting on following my colleague around while we were carrying out our diving activities, continuously chewing on the top of his dive helmet the entire time we were in the water.
Their thick, rounded head is extremely tough, and on more than one occasion, it was used to ram my fingers into the tank wall when I was not quick enough to offer food.
Shark rays have teeth, like all sharks and rays. However, like many other members of this group that feed on crabs and shellfish, their teeth are small and blunt, and excellent at crushing. I can vouch for that from personal experience, as well.
Far from shy, these animals are beautifully charismatic and amazing examples of the strong personalities that sharks and rays are capable of showing.
Shark rays are widely distributed throughout the tropical and subtropical Indo-west Pacific. Their Australian distribution covers the entire top half of the country, from Exmouth Gulf in Western Australia to central/northern New South Wales.
They prefer shallow in-shore habitats to around 70 m deep on the continental shelf.
Sadly, a recent re-assessment of shark rays by the International Union for Conservation of Nature (IUCN) determined that, globally, these rays are now ‘Critically Endangered’. This is a major change from their previous assessment of ‘Vulnerable’ just two years previously.
The IUCN as stated that the rhino rays, in general, are being pushed to the brink of extinction.
These animals are now considered to be the ‘most imperilled marine fish families’.
Population numbers of some of the rhino rays, including the shark ray, have dropped more than 80 per cent in the past 30-45 years.
The sudden change in status and severe declines in population numbers have come as a result of the intensification of unregulated fishing activity over much of these animals’ Indo-Pacific range.
The large, ‘white’ fins of these rays are considered to be of top quality, and as a result, they fetch some of the highest values in the shark fin trade.
Rhino rays are also fished to meet local demands for meat and other shark and ray products.
These animals are facing further threats from the loss of suitable inshore muddy or sandy habitats due to dredging, land reclamation activities and the loss of mangroves.
The good news is that Australia appears to be providing a bit of a refuge area for these rays. They are not targeted by fishery operations here, bycatch reduction devices have reduced accidental catch and their marine habitat is better managed, overall.
It is these sorts of initiatives that are needed more broadly in order to bring these incredible animals back from the brink.