Poor Knights marine reserve
by Dr J Floor Anthoni (2007)
|Three species, three kinds
In New Zealand we have three species of stingray, the eagle ray, the short-tailed stingray and the long-tailed stingray. It so happens that all three can be encountered on the poor Knights, an unusual coincidence because the eagle ray is mainly a coastal and estuarine stingray, and the long-tailed stingray has reduced its range considerably in the past decade, and can now mainly (only?) be found on the Poor Knights. It has disappeared from coastal waters and is not found south of Auckland, although identification guides still mention its southern range as Cook Strait (Wellington) and its habitat as estuaries and muddy areas.
Sting rays belong to the 'primitive' cartilaginous fishes, as opposed
to the more 'modern' bony fishes, but in evolution they have in fact become
quite advanced. For instance they have internal fertilisation and bear
their young live. A female stingray has usually only two babies, which
after birth, have to fend for themselves. Contrary to the 'modern' fishes,
whose offspring float away on ocean currents, a stingray's babies are born
where the mother lives. This may explain why populations can maintain themselves
well in remote places like the Poor Knights Islands.
The difference between males and females can easily be seen as males have two claspers trailing under their tail flap.
|The eagle ray (Myliobatis
The NZ eagle ray (Maori: Whai keo) can be distinguished quite easily by its whip-like tail (tenuicaudatus=thin-tailed) looking like a car antenna. At the base of this tail is of course found its sting, but also a small back fin, which is absent in the two other species. The eagle ray has a head and shoulders and pointed wings. It is usually grey to black above with a white belly but can also be yellow-green to brown on top.
On the Poor Knights, eagle rays are not very common. They must be feeding
from large snails like the Cooks turban snail, but I've never seen broken
fragments of such. The Poor Knights does not have cockles or scallops,
the preferred food of eagle rays.
stingray (Dasyatis brevicaudata)
The short-tailed stingray could well be the most common one on the Poor Knights and outer island of the east coast of the North Island, but it is not common on the South Island. In places it grows as large as a man, standing with outstretched arms, as can easily be measured from the large imprints found in the sand. Bigger ones still have been seen (and caught) with a wing span of up to 3.5m!
As scavenger, the short-tailed stingray must be able to find food easily
from occasional deaths in schooling fish.
stingray (Dasyatis thetidis)
The long-tailed stingray is dark olive to black on top and entirely white underneath without a grey margin. It is immediately identified by its very long tail, twice the length of its body. This stingray stays much smaller than the short-tailed stingray, reaching a wing span of about 1m. It can be approached easily as it is not aggressive. At the Poor Knights, these stingrays can be found resting by day in the shallow sand of Nursery Cove and the Labrid Channel.
in the archways
The Poor Knights have become famous for their socialising stingrays, particularly those seen in Northern Arch. At one time I counted 53, and on one of the photos below one can count as many as 26! But what are they doing there?
In recent years, scientists have made exaggerated claims about sharks'
and rays' ability of sensing electrical currents, to the extent that these
animals here in New Zealand could sense a car battery being dumped in the
sea at the other end of the ocean (10,000km away). This ability, it is
reasoned, enables them to read an internal compass to navigate from the
mainland to the Poor Knights and back.
The real reason for this behaviour is quite simple although also quite unbelievable. Stingrays do not form pair bonds, and must therefore pair up for mating, at the beginning of every year. Here in NZ, it happens in spring, in the months September to November (not entirely sure of this). Having dived on the Poor Knights since 1978, I have witnessed how it happened. In the beginning, there were no stingrays in Northern Arch, but then one day it began with only a couple. I observed that they were teaching themselves how to hang-glide in the rising current. Stingrays have no swim bladders, so they sink as soon as they stop swimming. But here they discovered that they could stay suspended, without swimming.
The next year there were a few more, and the year thereafter a few more, until one day I counted 53, half of whom were not quite capable of hang-gliding yet, as they tried to figure out what the others were doing. The diagram below shows the situation at Northern Arch, where currents rise over the sil at the bottom, causing uplift. Along the sides, the currents speed up, which can in theory also support hang-gliding, but this is very difficult indeed. The best positions are somewhere towards the lower middle, and there is some competition for these spots.
When the current stops, the fun is temporarily over, and one can see
them all just flapping around. No sooner has the current returned, and
the adept ones, take up their positions again. In Tie-dye Arch, which is
fully submerged and has a n extensive flat bottom, the currents distort
mainly at the top, where they exit. So one finds the stingrays hovering
Hovering in the current, or hang-gliding is not unique among stingrays, although their aerodynamic shape is just so perfect for this, with large horizontal planes. Many other fish species practice it, such as butterfly perch, blue maomao, pink maomao, snapper, tarakihi, giant boarfish and undoubtedly many more. For the photographer it offers a unique opportunity to obtain a stationary shot of otherwise ever moving fish.
The photo below shows four young giant boarfish hang-gliding behind
a rocky wall at 20m depth. The biggest one just detached itself from the
strict formation that lined up their eye patches, as it comes for a closer
inspection. Notice their long backfin rays that shrink as they grow. Notice
also their large breast and hip fins, acting as ailerons (wing flaps).
There is also this poor tarakihi who by his lonesome sought company with
the boarfish on account of their superficial resemblance by a dark patch.
The tarakihi is closely related to the porae, both having long breast fins
that could act as ailerons.
As an underwater photographer, I am privileged to be able to document many experiences. As every photographer knows, what makes it to film is only a small part of the total experience, and there remains much just recorded by the grey matter in one's mind. Yet these experiences need to be told, so that a more complete picture emerges of diving in New Zealand and the Poor Knights.
|The smart kingfish and the decoy ray
In Nursery Cove I was watching a young kingfish, no larger than 50cm, hunt a school of young koheru. In this he was spectacularly unsuccessful, as these fish dodged him and even out-swam him at every lunge he made for them. This in itself is astounding, because the laws of physics insist that small fish cannot outswim larger ones. Yet they did, and with a wide margin.
When koheru are catching morsels of food, they are in a loose schooling formation, but as soon as panic arises, they group into a tight oval ball which acts like a much larger fish, propelled by a mysterious jet motor. The principle of a jet motor is that its thrust equals the amount of water jetted out, multiplied by speed. Apparently the little fish, by moving their tails and bodies in unison, are capable of pumping a strong thrust that moves them forward with least friction, while also satisfying the laws of physics for bigger fish. They outswim the larger kingfish as it is not jet-propelled.
This shows clearly why it is necessary for kingfish to hunt in packs, for this causes confusion amongst its prey, and like wolves, the kingfish can surround the school of little fishes.
Now, this little Kingfish became visibly tired and disappeared, only
to reappear hiding underneath a long-tailed stingray (see photo). His plan
would have worked had the stingray not been annoyed with this object underneath,
that prevented it from landing on the sand. So it began to shear tightly
over the stalked kelp, trying to rub the little blighter off. All this
foiled the little kingfish' plan, although he was nearly successful.
|The giant short-tailed stingray
During a lonely dive at the Mokohinau Islands, at the northernmost tip of Burgess, where an exposed canyon loops around a large rock, it was rather dark due to all the foam on top. And as I swam over the egg-sized loose pebbles, the bottom changed into smooth rock, and then pebbles again. It took me quite a while to realise that this smooth rock was rather unusual. As I turned around, I saw that I had been swimming right over the back of a gigantic stingray, so big that I could not believe (comprehend, really) what I saw.
I'd like to share with you the internal turmoil inside me when I finally realised what I was looking at. First I swam squarely over the back of this stingray, thinking it was a rock. Then 4 metres further, it dawned upon me that the smooth rock I saw, was strange. I stopped and looked back and I didn't see the stingray. I backtracked to touching distance and still didn't see it. My mind could not see it because it didn't match any of the previous images of stingrays in my mind. I couldn't see it because it was so big. Yet, the tail was there, like one that stingrays have. Then finally my brain began to accept a new dimension and slowly I could see the rock for a sting ray. And guess what? A wave of emotion overcame me - not fear at all - but a kind of emotional discharge like when firmly held belief is proved wrong, and finally accepting the truth. I began to snotter for no apparent reason.
Apparently our brains are resisting anything that overturns previous experiences. Apparently our eyes can see only what we expect to see, and as soon as it differs by a whole dimension, we can not see it. And when we finally come to grips with it, it goes with strong emotions. Think about this when going into a new environment, like diving.
who fell in love with a diver
My buddy and I were diving on the sand on the southern end of The Labyrinth when we noticed three young female long-tailed stingrays on the sand. Nothing special, except that these pointed their stiff tails right up, instead of holding them down over the sand. Ignoring them, we busied ourselves filming a sharp-nosed pufferfish, when one of the rays came really close.
Back on the boat we couldn't get over our surprise and excitement, trying
to explain what we had experienced. The closest explanation is that these
young female stingrays were somehow on heat and mistook us for mating partners.
Hunters have often reported that young does (female deer) in their first
season on heat, come snuggling up to them, quite overwhelmed by feelings
inside, yet not knowing what to do. Perhaps this was also the case with
our stingray girls?
|Riding a stingray
On the sandy patch between Ngaio Rock and the Natural Bridge, longtailed stingrays sleep after a night's loveplay. We have always wondered whether one could play with these animals, like holding one by its tail and 'riding its tail' by steering it. The crucial bit comes in two steps: first you must approach without the stingray scurrying away. Instilling trust is a slow process that can easily go too fast, resulting in flight. We had seven stingrays here, so perhaps one would be brave and willing.
I have done this once more since, on a lonely dive without bystanders
and cameras. What an experience. To imagine a totally wild animal, very
much smaller than me, having enough sense to understand what play is, and
then enough courage to give it a go!
|Feeding the stingrays in the Garden
of Eden, Mokohinau
A German visitor once wanted to swim with dolphins - no problem. On average, one encounters a pod once every 15-20 nautical miles, so we set out on a tour from Leigh via Kawau, past Little Barrier, skirting Great Barrier and ending up at the Mokohinaus. No dolphins in a hundred nautical miles!
And yes, the Roggen were still there. I noticed that they were looking for something, and then that a yacht was filleting its snapper catch above, the carcass frames raining down. But the rays were seeking by smell rather than by sight. So I took a couple of carcasses and held one up. After three overflights, one ray got the message and took the frame from my hand, ever so gently. Rather than swallowing it as other fish would, its jaws crunched the skeleton like a mulcher would. All the while the ray fluttered around. Once it had completely crunched the meal, it came back for more. In the meantime, the second ray had learnt the routine. My German friend was over the moon, and as he had a video camera, returned home very satisfied. Sorry for the lack of dolphins.
For myself, it was a lesson in how quick completely wild animals can
overcome their fears, and then learn something they have never done before
in their lives. It taught me never to underestimate stingrays. It was also
the beginning of my suspicion that there is something entirely wrong with
the sea. For where have all those dolphins gone?
|The spearo attack
After the Goat Island marine reserve was opened, researchers often took their raw material from the reserve, and if this was fish, it needed to be speared selectively (The Department of Conservation did not exist back then). One young scientist was particularly good at that, and often did the work for others.
So this scienctific-spearo had been sniffed by a large stingray, and
as he was surfacing, suddenly the whole world went dark as this stingray
wrapped himself around the diver with its large wings, and would not let
go. The story is that the spearo peed in his pants, because he was unable
to move his hands and could not reach for his knife. Several frightening
minutes passed until finally the ray let go. Fortunately this spearo was
very experienced and did not panic. And the fish? The ray took the lot!
|The Cayman Island stingrays,
the experience of George Wauchope
Most people hold the misinformed view that stingrays are dangerous creatures
that must be avoided at all costs. This is simply not accurate. This irrational
fear mainly stems from the infamous death of Steve Irwin (the “Crocodile
Hunter”) on the 4th September 2006. Many people believe that since Irwin
was killed by a stingray, that all stingrays are dangerous, but this could
not be further from the truth.
The Cayman Islands are a group of three small islands in the Caribbean. Here are many species of Stingrays, all of which are completely safe. The “Southern Stingray” is found throughout the Caribbean and lives a peaceful and docile life. Grand Cayman is home to “Stingray City”, which is the pinnacle of human-stingray interaction. This is a shallow sandbar (2-3 feet deep) where you can hand-feed the Southern Rays. Thousands of tourists flock here every year, and virtually no one has issues. There are extremely rare occurrences where a stingray’s barb cuts someone, inducing short term, non-life threatening damage; however, these situations are always caused by people stepping on the rays through careless behavior.
Most people who visit “Stingray City” are scared at first, because Steve
Irwin’s experience lurks in the back of their minds; however, as soon as
they enter the warm shallow water, they realize there is no threat posed
by the rays.
December 2016, George Wauchope - https://www.stingraycitygrandcaymans.com/
|... wishing we were there|
Pryce the "ray whisperer" cuddling a Cayman stingray.
left:George Wauchope on his ship.