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Norfolk Island's Reef

Discover a fragile paradise – Norfolk Island's beaches, lagoons and coral reef
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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.

This blog is rated in the Top 20 Coral Reef Blogs in the world.

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Surge wrasse - Thalassoma purpureum

Nuptial colouration in blennies

October 12, 2021

It has been a stellar long weekend here on Norfolk Island. Show Day yesterday saw everyone out enjoying themselves, admiring the exhibits and catching up with friends. We have been very lucky here with regards to the pandemic. So far. But we mustn’t be complacent.

A couple of weeks ago I mentioned the Lady Musgrave blenny, Cirripectes chelomatus, and how I anticipated they would be changing colour any day now. Sure enough, I photographed one individual on 5 October, and he was dark in colour with just the teeniest beginnings of a colour change showing. That same individual now has his best bib and tucker on just five days later – presumably looking for a like-minded blenny to share red wine by the fire and moonlit beach walks! I am very confident this is the same individual. I visit him all year long (and we are on first name terms!). This is a remarkable change. On iNaturalist, a citizen science site for posting observations of plants and animals, the identifier of my observation referred to it as ‘nuptial coloration’. There’s a great little article on this phenomenon here: ‘Men With Style – Nuptial Colouration in Fish’.

View fullsize Lad Musgrave blenny, 5 October 2021
Lad Musgrave blenny, 5 October 2021
View fullsize Lady Musgrave blenny, 10 October 2021
Lady Musgrave blenny, 10 October 2021
View fullsize Pacific rockcod - Trachypoma macracanthus
Pacific rockcod - Trachypoma macracanthus
View fullsize Norfolk cardinalfish, male on left
Norfolk cardinalfish, male on left

In the water has been fantastic, too. It is warming up, and with that some small changes in behaviour are apparent. For example, the Norfolk cardinalfish, Ostorhinchus norfolcensis, are pairing off. These guys are mouth breeders, so the male keeps the eggs safely in there until they hatch. I did a story about them on this blog last year. It is fascinating, so do check it out. There were plenty of Pacific rockcod, Trachypoma macracanthus, hanging around down in Slaughter as well. Preferring to hide under reef overhangs, it is lovely when you catch one out in the open. Such a splash of colour.

At the far end of Slaughter Bay, almost as far as you can go before you hit the shallows near the pier, I came across our resident female southern eagle ray, Myliobatis tenuicaudatus. She has been around quite a while – I’d love to know how long – and is easily recognised because of her stumpy tail. She ranges throughout the lagoons, and in fact the next day I saw her just off Lone Pine. She was totally unconcerned as I watched, approaching me as she concentrated on bashing down into the sand to find some tasty morsels. An inscribed wrasse, Notolabrus inscriptus, followed her closely, just in case she missed something!

View fullsize Southern eagle ray - Myliobatis tenuicaudatus
Southern eagle ray - Myliobatis tenuicaudatus
View fullsize Inscibed wrasse waiting behind
Inscibed wrasse waiting behind
View fullsize Southern eagle ray - Myliobatis tenuicaudatus
Southern eagle ray - Myliobatis tenuicaudatus
View fullsize Inscribed wrasse just behind
Inscribed wrasse just behind

I also took some more photos of under the raft. I have discussed this before, here. But, in brief, over the years the raft has provided shelter beneath its timbers for a thriving fish nursery. Beneath the raft was an amazing sight, teeming with fry. I have photos of it before it was rebuilt with flotation tanks in the spaces between the timbers, and since. For whatever reason, the fish simply have not used the raft that much since it was rebuilt. We have had no babies to speak of under here since we got the new design. Those we do get can’t hide from the trevally as they sweep past in a pack hunting for a meal. How this translates to numbers of fish at large in the bay, I have no idea. I’ve only posted a photo from before and from this week on here. I’ve recorded the whole story every month in between, and nothing.

View fullsize The old raft, 24 April 2020
The old raft, 24 April 2020
View fullsize The new raft, 10 October 2021
The new raft, 10 October 2021

In last weekend’s newspaper, we had the monthly newsletter from the Administration in which he spelled out the issues with the water quality around the island, and particularly in the lagoon areas. On one hand, it is sad to see, but also, it has been something of the elephant in the room. Now we have recognition of the problem by the Commonwealth Government, then perhaps we are on the path to realising a solution. And we need a solution very soon. You can find more on my thoughts about the situation in this article, here, ‘The State of Play on Norfolk Island’s Reef’.

Until next week … 

Tags nuptual colouration, Blenny, Emily Bay, Raft, pontoon, Southern Eagle Ray, environment, ecosystem, water quality
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Featured
Norfolk’s water quality – when action is reported as outcome
June 15, 2026
Norfolk’s water quality – when action is reported as outcome
June 15, 2026

A recent Australian Government media release presents investment, monitoring and catchment works as progress on Norfolk Island’s water quality. Some of that work is useful, and some of it was badly needed. But activity is not the same as proven improvement. This post looks at Kingston sewerage, wetlands, cattle, acid sulfate soils, groundwater and reef health, and asks whether Emily Bay and Slaughter Bay are actually being better protected.

June 15, 2026
How surgeonfishes got their name
June 14, 2026
How surgeonfishes got their name
June 14, 2026

Surgeonfish are named for the sharp little scalpels near their tails, but on Norfolk’s reef their more useful work happens at the other end. Pencil surgeonfish, bluespine unicornfish and their relatives help browse algae across the reef – a small daily job that becomes very valuable on an algae-rich lagoon reef like ours.

June 14, 2026
A shrimp storm
May 28, 2026
A shrimp storm
May 28, 2026

While setting my research cams last week, I swam into what looked like an underwater snowstorm. It appeared to be the aftermath of a mass moulting event, with large numbers of tiny, translucent shrimp-like exoskeletons drifting together near the surface.

May 28, 2026
Kingston dredging: what happens when a reef does not fit the framework
May 28, 2026
Kingston dredging: what happens when a reef does not fit the framework
May 28, 2026

This correspondence with DCCEEW is about more than one dredging proposal. It is about what happens when an ecologically distinctive place is assessed through standard tools that do not always make its most important values easy to see. I am publishing it here because that is something we need to be aware of, both on Norfolk Island and more broadly in Australia.

May 28, 2026
Kingston dredging: the project advances, the questions remain
May 24, 2026
Kingston dredging: the project advances, the questions remain
May 24, 2026

Kingston dredging is edging closer, and the paper trail is growing. This post brings together earlier correspondence with the Department and the latest media release so readers can see what has been asked, what has been answered, and what still remains unclear about the project, its rationale, and the protections proposed for the reef.

May 24, 2026
The lime-green coral in Slaughter Bay – a 40-year paper trail
May 17, 2026
The lime-green coral in Slaughter Bay – a 40-year paper trail
May 17, 2026

Green Mountain – the name I give this coral in my database – is a coral I’ve photographed for years as I swim past. Then I found its backstory in the Norfolk Island National Parks archives: a rough map, reused paper, a note in the margin – ‘still thriving’. That’s how baselines begin.

May 17, 2026
What Norfolk Island’s reef tells us about environmental blind spots
April 5, 2026
What Norfolk Island’s reef tells us about environmental blind spots
April 5, 2026

The Kingston dredging proposal on Norfolk Island raises a bigger question than dredging alone: how well do standard environmental assessment tools capture the real significance of a remote and unusual reef system like Norfolk Island’s?

April 5, 2026
Hammer coral time!
March 30, 2026
Hammer coral time!
March 30, 2026

Hammer corals have unique tentacles that are large, fleshy, and tubular; these terminate in a ‘T’-shaped, hammer-head or anchor. Beneath all these softly waving tentacles is an extraordinary skeleton structure, which helps define them as a large polyp stony coral.

March 30, 2026
Norfolk Island’s fishes: drifters, residents and the ones still missing
March 24, 2026
Norfolk Island’s fishes: drifters, residents and the ones still missing
March 24, 2026

Norfolk Island’s fish fauna reflects both connection and isolation. Some species may arrive from elsewhere as drifting larvae, some populations appear to persist locally, and some fishes known from islands on either side of Norfolk have still not been recorded here. This post looks at what old survey work, regional checklists and genetic studies suggest about that more complicated picture.

March 24, 2026
18 Jun 2025 (20)_crop.jpg
March 7, 2026
Alveopora or flowerpot coral – how to tell the difference
March 7, 2026

They look alike at first glance, but Alveopora and flowerpot corals are not the same. The easiest way to tell them apart is to count the tentacles.

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