Coral spawning, Norfolk Island 2021 — Norfolk Island's Reef

Out on A Swim

‘Out on a swim’ is a coral reef blog that tells the stories of the characters who live under the waves and what has caught my eye when ‘out on a swim’ in the lagoons of Norfolk Island. It is also a record of the difficulties Norfolk Island’s reef faces, like many others around the world, as a result of the poor water quality that has been allowed to flow onto it.

This page shows the most recent blog posts. For the complete catalogue, visit the ‘Out on a swim index’ page.

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Out on a swim in the lagoons on Norfolk Island on the morning of 27 December 2021, the mood was palpably different.

Call me fanciful, but I immediately noticed a frisson of excitement among the fish. Lots of activity and agitation. And all kinds of slightly unusual observations:

A fish over here, who always, but always, is found over there (many fish have very small home ranges and are quite territorial); the little scissortail sergeants (Abudefduf sexfasciatus) bobbing up to the surface more than normal, and taking big gulps; and the multispine damselfish (Neoglyphidodon polyacanthus) going bonkers over a couple of different corals.

So I do what I normally do – take photos, then go home and start trying to find answers to my questions.

I didn’t have to do much digging though. As I was driving home from my swim, my phone pinged a few times. Jim Castles the Australian Marine Parks manager on-island had messaged me with photos showing a slick of coral spawn floating in Ball Bay, a semi-circular bay formed from a volcanic imploding caldera on the south-east of the island. See the images and video, below.

A pink tide, Ball Bay

‘But this wasn’t supposed to happen until January!’ we both said!

Clearly nature had other ideas.

And for those who are wondering, remote Norfolk Island, just 5 km by 8 km in size, and about 1,600 km from the east coast of Australia and 900 km from Lord Howe Island, its nearest coral neighbour, is the second most southerly coral reef in the world. Consequently, our annual coral spawning takes place a month or more later than the Great Barrier Reef Marine Park. On Norfolk Island, the coral spawning event normally occurs eight to ten days after the full moon in January. Full moon will be on 17 January. But perhaps the full moon in January 2022 maybe a bit too late in the season, so December, it seems, it is!

At that point, I didn’t think Emily and Slaughter Bays had spawned, but the coral looked very ready. They take on a slightly fuzzy appearance as spawning time gets closer. The hammer corals (Fimbriaphyllia ancora), in particular, were looking rather fecund that morning, although most didn’t have the tell-tale pink in their tentacles. But one did! And the multispine damselfish thought that this was a very choice treat, as you can see in the image, below.

A hammer coral colony being grazed by multispine damselfish

A scissortail sergeant grazing on coral spawn that has come into the lagoon

Similarly, the scissortail sergeants were finding something on the surface worth eating as well.

So, although coral spawning had occurred outside the lagoons, and certainly at Ball Bay and Cascade, it looked like we are in for a coral spawning on the night of 27 December inside the lagoons.

Pink coral spawn floating on the surface of Emily Bay, Norfolk Island, 28 December 2021

And as predicted, when I went out for my swim on the morning of 28 December, this was the view from under the water.

Things weren’t quite as frantic in the lagoon on the morning of the 28th. I think all the full bellys had calmed things down, although there was still plenty of activity.

For example, normally our little butterflyfish get around in twos and sometimes threes. Occasionally you will see a few more together. I came around a corner of the reef to be greeted by a loose gathering of lots of butterflyfish all enjoying the coral spawn, which you can just make out floating in the water. My photo, bottom, really doesn't do the scene justice. There were lots of fish!

In my photo there are: bluespot butterflyfish - Chaetodon plebeius; blackback butterflyfish - Chaetodon melannotus; black butterflyfish - Chaetodon flavirostris; and the most numerous, threadfin butterflyfish - Chaetodon auriga. I’ve included their photos, bottom images.

Australian Marine Parks has placed larval settlement plates in six locations around Emily and Slaughter Bays, Norfolk Island.

Australian Marine Parks has placed larval settlement plates in six locations around Emily and Slaughter Bays. These plates have been curing for a few months in the saltwater near the Kingston Pier, but now they have been deployed.

These plates will give Parks Australia and researchers valuable information about the success of the coral spawning event. As the coral spawn disperses and settles in the lagoon, some of it will fall onto the plates. These will be collected and examined to determine diversity and density of coral larvae.

If you see them, please look, but don't touch. We need this valuable information.

An unusual loose gathering of butterflyfish in Emily Bay, Norfolk Island. The water column is full of pink coral spawn.

Bluespot butterflyfish

Blackback butterflyfish

Black butterflyfish

Threadfin butterflyfish

November 3, 2026

Familiar faces – getting to know the reef’s residents

Six years of swimming the same little reef have introduced me to some unforgettable characters that I’ve followed over time. From familiar fish and anemones to turtles and a snail’s eggs, this final article in my photographic series explores what I’ve learned about the lives of individual animals simply by returning, watching and taking photographs.

November 1, 2026

When algae move in – the changing reef neighbourhood

Algae are a natural part of Norfolk Island's reef, changing with the underwater seasons. But sometimes their beautiful green growth conceals a rather sad story. In the fifth article of my six-part photographic series, I revisit familiar places to see how algae have changed over the years – and what might be hiding underneath.

October 30, 2026

The slow disappearance – disease on the reef

What happens after coral disease has run its course? In the fourth article of my six-part photographic series, I revisit colonies I've watched lose living tissue, sometimes alarmingly quickly. From a potentially century-old brain coral that lost most of its living tissue in less than 100 days to the algae-covered skeletons left years later, these photographs reveal the longer-term consequences of coral disease on Norfolk Island's reef.

October 28, 2026

When storms rearrange the reef

Sometimes the sea rearranges a reef in a matter of hours! In the third article of my six-part photographic series, I revisit corals broken, overturned or swept away by powerful swells and storm surges. Some disappeared altogether, while others found surprising ways to survive. Five photographic sequences reveal just how dramatically Norfolk Island's reef can change.

October 26, 2026

When the reef fights back – coral growth and recovery

Not every coral story ends badly! Among six years of underwater photographs are some wonderful examples of growth, survival and recovery. From corals that have grown spectacularly to others that have survived bleaching, breakage or even being turned upside down, this second article in my photographic series celebrates some of the reef's more encouraging stories.

October 24, 2026

The neighbours – six years of watching the same reef

When I began photographing Norfolk Island's reef in 2020, I simply recorded whatever caught my eye. Six years later, those photographs have become a record of individual corals and their changing fortunes – growth, competition, survival and loss. This is the first of six articles looking back at what I've seen, and sometimes what I wish I hadn't.

October 10, 2026

Pulling the rugosity from out of the reef

What do ‘rugosity’, structural complexity and channeling your inner fish have in common? Quite a lot, as it turns out. This week I’m looking at how all the lumps, bumps, branches, holes and ledges on a reef create habitat – with a brief detour into one of my long-standing tricks for navigating tertiary study: write down the jargon until it starts to make sense.

September 27, 2026

How does a sea slug smell?

It started with a close-up of a little Elysia and two rhinophores that looked like tiny rolled-up scrolls. Once I noticed them, I started going back through years of sea-slug photos and realised just how wildly different these sensory organs can be – ridged, rolled, curled, tubular and, in sea hares, distinctly rabbit-eared. So this week’s rabbit hole is all about how sea slugs ‘smell’ underwater, and why their noses come in so many different shapes.

September 19, 2026

The Elite Fleet sails in

Nearly six years ago, my very first blog post was about the strange blue and violet creatures that live at the ocean’s surface – a group I christened Norfolk Island’s ‘Elite Fleet’. Since then I’ve seen plenty of bluebottles and the occasional violet sea snail, but never a by-the-wind sailor. Until this morning. Velella velella is not a true jellyfish, but a colonial hydrozoan with a transparent sail that lets the wind help carry it across the ocean. So what exactly is this extraordinary little creature, how does it ‘sail’, and what connects it to the rest of the fleet?

September 18, 2026

In a nutshell – where I stand on the proposed Norfolk Island Marine Park

I support the proposed expansion of Norfolk Marine Park and its renaming as Norfolk Island Marine Park. There is much to welcome – strong offshore protection, no mining, and recognition of the importance of sustainable local fishing. But I also have some reservations. Why does Cascade need to be removed from the Marine Park at all? How will more than 430,000 km² actually be monitored and enforced? How do we make sure Norfolk people have a genuine role in management? And, above all, how do we ensure that the enormous new park does not draw attention away from the small, stressed reef immediately beside us?