Stingray aggregation returns to the Poor Knights

This summer has seen the return of the famous Northern Arch stingray aggregation at the Poor Knights Islands, a spectacular occurrence that has seen divers flocking to the iconic site.

The return of the rays after nearly 18 years even made the news, and in contrast to the usual summer media reports of people being ‘attacked’ (read ‘stepping on them and getting spiked’), the coverage this year was all positive.

Stingrays are actually mellow creatures that tend to mind their own business, and incidents involving injuries are usually a self-defence reaction to being crowded or stepped on. Underwater, where both animal and diver can see each other, rays are a relatively safe creature to encounter, and getting close to one is usually painless and enjoyable.

Northern Arch, beautiful from the surface but giving no hint of the spectacle underneath

When it comes to seeing stingrays underwater, it doesn’t get any more impressive than diving with the Northern Arch aggregation, something I last experienced between 1999 and 2001.

This is a surreal experience drifting through the middle of the narrow 40m deep archway, the silvery surface 20m above, the bottom 20m below and the whole blue space filled from top to bottom with larjge black stingrays stacked layer upon lay er like squadrons of stealth bombers gliding back and forth.

Why do they congregate there? The prevalent theory is that it is a meeting place for male and female rays to find a mate, a sort of speed dating site! This is backed up by the number of females we see with fresh mating scars, scrapes and bite marks on their wings. Strangely though, despite diving in the Arch a lot over the peak years, and even doing several night dives hoping to film rays mating, I never saw a pair in the act. I did notice however that the rays dispersed out from the Arch at night, so perhaps mating happens out over the deep sand or reef terrain.

Encounter with an extremely rare white ray (not an albino) in Northern Arch nearly 20 years ago

Interestingly during mating season the teeth of mature male stingrays change shape and become sharper to aid in gripping the females during the act of copulation, a clever adaptation for a creature built like a slippery frisbee.

The closest I came to seeing rays mate was while filming for ‘Our Big Blue Backyard’ in 2014 when a male was attempting to mate with an unwilling and bad-tempered female.

After being rejected the frustrated male then swam over and rubbed up against me until he realized his mistake…luckily for me!

In the peak year, 1999, I witnessed upward of 70 rays stacked in the Arch on days with a good current; the summers of 2000 and 2001 were also big stingray years. After 2001 however the numbers dropped off dramatically to only 10 to 15 rays at a time, then subsequently down to just 5 to 10 on a good day. Until January this year with up to 30 or 40 rays back in the Arch.

A short-tail ray shows off his white belly in the arch

There are lots of theories why they have not been around in large numbers for the past 18 years. One of the favourites is that Orca scared them away after several occasions during 2001 where Orca stopped by the Poor Knights to feed on them. They definitely left a few scared rays and a lot of ‘ray apple cores.’

But undermining this theory is that they returned to normal numbers in subsequent years everywhere else around the islands, other than in the Northern Arch. I think it is a safe bet Orca have hunted rays around the ‘Knights on and off for a very long time, and the sporadic times they pass through the reserve is not enough evidence to say they drove the rays away for nearly 20 years.

Long-tail rays are the other common species seen at the Poor Knights and are generally seen on sandy patches in ones and twos

A more likely-factor is the disturbance caused by concentrated diver numbers visiting Northern Arch to dive with them during their aggregation period; it doesn’t take many divers blowing bubbles to turn the archway into a 40m deep spa pool with a bubble curtain from top to bottom! The rays react to bubbles quite strongly tending to move out of the arch until the bubbles thin out again. So it is possible that after a few years of this they sought somewhere else to meet up.

Naturally with the stingray aggregation such a spectacular sight it is a major attraction for divers to the Poor Knights – myself included! It’s an event none of us want to miss, so implementing a few simple measures to minimize ‘diver disturbance’ at this one, specific dive site would help ensure the rays continue to come back year after year for us divers to enjoy.

Stingray squadron silhouetted against the blue

Perhaps it’s worth trying things like spreading out the timing of dive boats at the ‘Arch so there is an hour or so between dives to give the rays some ‘alone time’; encouraging divers to hang in the archway entrances rather than right in the middle of the Arch; suggesting divers do this particular dive in small groups, and making people aware that freediving/snorkeling with the rays can be just as spectacular as scuba diving with them. Actually it can be a more interactive experience than on scuba as the rays barely move aside for divers who are not blowing bubbles.

Something I filmed back in 1999 and 2000 and haven’t seen in this latest recurrence of the stingray aggregation at Northern Arch are the two pure white rays that used to occasionally show up amongst all the regular dark stingrays – a surreal sight! I often wonder what happened to them and whether we will ever have another white ray show up at the ‘Knights…obviously they are an extremely rare morph. Black or white, I’m crossing my fingers the rays show up in big numbers again next summer!

Stingray squadron silhouetted against the blue

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