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.

‘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.

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.

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. 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.