Increasing Occurrence of Stingrays on White Shark Cage Diving Trips

stingrays on White Shark Cage Diving TripsThere has been an increased amount of stingray activity during shark cage diving trips on our boat, Slashfin.  The first occurrence was on the 6th of January on our morning trip.  We had a stingray (about 1.5m in length) come up to our bait line and nearly attempt to take a bite (the front of the disc actually came out of the water).  While this was going on, there was a 2 meter Great White Shark interested in our seal decoy (only about 8-10 meters away).  The two animals turned and swam towards each other until they were about 1 meter away, at which point they both seemed to get spooked and swam off in opposite directions.  This interaction is the first known of its kind, a surface interaction between a great white shark and a stingray.  Since this day we have noticed the rays coming up to the surface more often, on one occasion coming close enough to the back of the boat that we were able to get underwater footage of it free swimming.  

Increasing Occurrence of Stingrays on White Shark Cage Diving TripsAfter examining photographs and videos of the rays we have seen, it seems that the species that has been visiting us is known as a short-tail stingray (Dasyatis brevicaudata).  It is a very common species, and it is found here in South Africa.  It has been seen the shallows in both New Zealand and Australia, but is commonly found at depths of 180m or more.  It has been seen in both shallow in New Zealand and Australia, but is commonly found at depths of 180m or more.  Given that knowledge, it has been documented to move into shallow waters with rising tides, which could be one reason why we have seen them some days and not others.  The short-tail stingray is the largest species of ray in the world, growing upwards of 2 meters in length (the ones we have seen have been between 1 and 1.5 meters respectively).  This species is primarily benthic (bottom-dwelling) in nature, feeding mainly on benthic fish and invertebrates, but it is also known to move up into the water column regularly where it will feed on fish and other small animals. 

While it is not necessarily a surprise to see this species moving high into the water column, it is worth noting that they are doing this in the presence of great white sharks, a suspected predator of short-tail stingrays.  Another question to ask is why is this happening so often now, when previously these behaviors of coming up to bait lines and cage diving boats were almost unheard of.  It will be interesting to see if this trend continues, and what explanations we will be able to come up with elucidate this interesting behavior.

Check out the first sighting below Fasttrax was on board and recorded the footage below – you can feel the excitement of the guests on board

Matt Nicholson (Marine Biologist, marine Dynamics)

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