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BYRON BAY’S PLAGUE OF RAYS

by Nigel Marsh and Helen Rose

 

We had started the dive hoping to encounter a manta ray, but all we were seeing were its smaller cousin, the blue spotted stingray. It started out being only one or two stingrays, then groups of four and five, and then groups of ten or more. But nothing could have prepared us for the number of blue spotted stingrays in the gutter before us, there were hundreds of stingrays swarming about, literally a plague of rays!

 

We were diving Byron Bay, one of Australia’s most popular holiday towns on the northern coast of New South Wales. Off the town are a number of wonderful dive sites with the most popular being Julian Rocks. A marine reserve since 1982, Julian Rocks is always a brilliant dive and home to masses of fish, turtles, a diverse range of invertebrate species and a great collection of sharks and rays.

 

The dive had started out very ordinary, Jai our skipper from local dive operation Sundive had tied up to the mooring on the western side of Julian Rocks at a shallow site called The Nursery. We were diving in January and only days before the visibility had been 30m plus, but after a few days of northerly winds we now had greenish water surrounding the boat. Entering the water the visibility was a patchy eight to 12m, just acceptable for photography.

 

The Nursery is usually a good spot for photography with plenty of invertebrate species found amongst the hard corals and boulders. We soon found octopus, moray eels, ornate wobbegongs, a shy blind shark, several cheeky blue gropers and quite a few blue spotted stingrays, but none more than usual. Reaching a depth of 14m we encountered several leopard sharks patrolling the reef edge and disappearing in and out of the gloom, while above mackerel and barracuda swam by.

 

Reaching the southern end of Julian Rocks we were in an area of gutters and bommies called The Needles. This was where a manta ray had been seen the day before, but we couldn’t find it, instead seeing more leopard sharks, turtles, wobbegongs and several large black blotched stingrays. We also started to see an unusual number of blue spotted stingrays, dozens of them in small groups.

 

The blue spotted stingray or maskray (Dasyatis kuhlii) is one of the smallest species of stingray, reaching 50cm in width, and found in tropical waters throughout the Indo-Pacific region. Although encountered on the Great Barrier Reef (where they are smaller and have distinctive white bands on their tails), we have found them to be more common in Southern Queensland and Northern New South Wales where you can typically see a dozen on a dive. However, on this dive we had already seen over fifty of these small rays, more than on any previous dive.

 

We then reached a wide sandy gutter called Elwood’s Trench where a spotted eagle ray was feeding on the bottom. Even more blue spotted stingrays were gathered in this gutter; resting on the sand, under the sand, on top of each other and swimming about. Doing a quick count we could see over thirty rays in the gutter before us. Some of the rays were heading up the gutter, so we followed, and the further we went the more numerous the rays became.

 

As the sand at the end of the gutter gave way to a boulder slope the rays appeared to thin out, but then we realised that the boulders were covered in a seething mass of rays that was constantly moving. As we watched hundreds of blue spotted stingrays were fluttering over the rocks, swarming up and down like a giant flock of birds.

 

This was just amazing, we had never seen so many stingrays gathered together in an aggregation like this, there must have been over five hundred stingrays and they were constantly being joined by more rays coming up the trench. The scene before us was just chaotic, the swarm heading in every direction, groups would break from the pack and swim over the sand and settle on the bottom, while the rest continued to flutter up and down the rocky slope. Also joining in the action were several very large black blotched stingrays, white spotted shovelnose rays and schools of kingfish, trevally, snapper and sweetlips.

 

Why were all these blue spotted stingrays aggregating in this gutter, we started to wonder? They weren’t feeding and they weren’t breeding, as far as we could tell. We have witnessed breeding behaviour in this species before in spring time, with male and female rays pairing up. We also once saw a male biting a female’s tail and being towed around the reef, but have never seen mating.

 

A closer look at the rays revealed that the majority of them appeared to be females (hard to tell with this species as the claspers are so small on the males). Were they gathering together for breeding, or had they already breed and were gathering together to pup? Stingrays give birth to live young, the young around 16cm wide in blue spotted stingrays, but they usually have two distinctive bulges in their back when pregnant, and none of these rays had those bulges. We exited the water amazed by this aggregation of stingrays, but also puzzled as to why they had gathered together.

 

Returning to Sundive between dives (Sundive operate single dives on their two rigid hull inflatable dive boats) the other divers in our group had seen plenty of blue spotted stingrays, but none had been into Elwood’s Trench to see the aggregation we had witnessed. Discussing the aggregation we knew other species of rays that school, such as mobula rays, cownose rays, manta rays and eagle rays, but these species school together for feeding or protection, not in the chaotic gathering we had just seen.

 

Schooling behaviour is far less common in stingray species, the only time we had previously seen a school of stingrays was at Manta Bommie off Brisbane, where groups of up to twenty pink whiprays (Himantura fai) swim around the reef or rested on the bottom together. The most famous gathering of stingrays is at Stingray City off Grand Cayman in the Caribbean, where several dozen whiptail stingrays (Dasyatis americana) gather together in shallow water, but this is to get free food.

 

We knew of only two species of stingray that school for breeding, the short-tailed stingray (Dasyatis brevicaudata) at the Poor Knights off New Zealand and the marbled stingray (Taeniura meyeni) at Cocos Island. However, both these aggregations are mainly of males, schooling together and pursuing any female that ventures into the group.

 

Returning to Julian Rocks for a second dive, Jai this time tied up to the mooring just near Elwood’s Trench. We first decided to head into nearby Hugo’s Trench to see if the blue spotted stingrays were also gathering in here. This deep trench is always full of life, we swam over spotted wobbegongs littering the bottom, saw several turtles, black blotched stingrays, a black cod and schools of bream, sweetlips, red morwong and stripeys, but only a handful of blue spotted stingrays. Time to go back to Elwood’s Trench!

 

As we entered the trench the number of blue spotted stingrays seemed to have thinned out, there were now barely a dozen in front of us. Had the stingrays all disburse during our surface interval? We headed up the trench thinking that the rays had departed, but there were a few rays still around and they were all heading towards the end of the gutter.

 

Arriving at the end of Elwood’s Trench we were relieved to see that the stingrays were still there, and many more than before. There were now several hundred blue spotted stingrays covering the sand and probably over a thousand swarming over the boulders. Where had all these rays come from? We hadn’t realised that there were this many rays in the area.

 

We shot more photos as we swum amongst the rays, they hardly noticed our presence, swimming around us and reacting more to the rays around them. Observing the rays for any clues to this gathering proved futile, it was just a seething mass of blue spotted stingrays. Groups were lying on the bottom, other groups were swimming around, there didn’t appear to be any centre of action, just mass chaos.

 

We wanted to get photos of the main mass of rays on the boulders, but this was hopeless as the bottom was too stirred up by the sheer volume of rays. So we stayed on the sand, in the clearer water, where we could still frame fifty or more rays in one photo. After twenty minutes with the rays our bottom time was running low so we reluctantly left this amazing aggregation of blue spotted stingrays and headed back to the boat.

 

Later speaking to Phil Buckland, one of Sundive’s most experienced dive guides, he informed us that the blue spotted stingrays had been building in numbers for about three weeks, and that this was an annual event. We had always avoided Byron Bay in mid summer, because of the holiday crowds, so had missed this spectacular gathering of rays in the past. Phil also added that the rays would probably be around for another week or so and then suddenly depart. We speculated as why the rays were aggregating. Mating? Feeding? Group pupping? But we couldn’t come up with any answers.

 

We will be looking forward to next summer to visit Byron Bay again to see this ‘plague of rays’ and who knows, we many discover some clue as to why these blue spotted stingrays are aggregating at Julian Rocks.

 

BYRON BAY’S WONDERFUL DIVE SITES

Julian Rocks is the premier dive site at Byron Bay and can be dived under most conditions. Around ‘The Rock’ are numerous named dive sites in depths from 6m to 25m. The Nursery is an area of shallow coral gardens on the western side of Julian Rocks. In deeper water from here are a series of gutters known as the Wide Trenches, which are popular with grey nurse sharks. At the northern end of Julian Rocks is the famous Cod Hole, a large swim-thru cave always packed with fish.

 

On the eastern side of Julian Rocks are more caves and gutters to explore at Cray Cave and Gorgonian Hollow. Heading south you next reach Hugo’s Trench, a deep channel that is always overflowing with fish, wobbegongs and turtles. At the southern end of Julian Rocks are more gutters at The Needles, and another impressive channel at Elwood’s Trench, plus more reef and bommies in deeper water.

 

In calmer conditions divers can also explore the nearby rocky reefs at Spot X, Mackerel Boulders and Kendricks Reef. One of the most spectacular dives sites in the area is Cape Pinnacle, a colourful pinnacle in depths from 25m to 40m that always has a lot of action.

 

Byron Bay also has a couple of good shore diving sites, as right off the main beach are several shipwrecks that went down when Byron Bay was a port. The Wollongbar is very broken up, but the Tassie II is always an interesting dive as the hull is full of wobbegongs and other fish and only 5m deep.

 

BYRON BAY’S RICH MARINE LIFE

The reefs off Byron Bay host a rich variety of marine life beside blue spotted stingrays. On every dive you will see colourful corals and a diverse range of invertebrate species, including a wide range of nudibranchs, shrimps, crabs and cuttlefish. A large variety of fish species are common to the area, from cheeky blue gropers, to colourful tropical reef fish and abundant pelagic species like kingfish, trevally, barracuda, mackerel and batfish. Byron also has a good range of critters from time to time, such as anglerfish, harlequin shrimps, leaf scorpionfish and the odd red Indian fish.

 

But the most spectacular species here are the sharks and rays. Manta rays are often seen over summer cruising around the reef or hovering over a bommie to get cleaned, while spotted eagle rays can be seen at anytime of the year. Other common ray species, beside the blue spotted stingrays, include large black blotched stingrays, common stingarees and white spotted shovelnose rays, and if you are lucky you may also see mobula rays, a short tailed electric ray, a black stingray or a school of cownose rays.

 

Grey nurse sharks are common around Julian Rocks for most of the year, apart from summer when they are replaced by dozens of leopard sharks. A look under ledges and plate coral might also reveal sleeping brown-banded catsharks or blind sharks. But the most common shark species at Byron Bay are the wobbegongs. Three species of wobby are found here, the spotted, ornate and banded, and they are found in such large numbers, especially over winter, that we have nicknamed Julian Rocks ‘Wobby World’.

 

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