Blog Post

All you need to know about the coral spawning

TNQ Writer

Strap on your mask and snorkel or oxygen tank for the Great Barrier Reef’s biggest event of the year – the beautiful and mysterious mass coral spawning. The 2018 spawning event is predicted to occur between November 26 and November 29.

What is coral spawning?

For 20-30 minutes the reef explodes with life

The annual event is incredible to go diving or snorkelling in

Coral polyps are like tiny upside-down jellyfish

In simple terms, coral spawning is the reef having sex. Coral polyps simultaneously release egg and sperm bundles that they’ve spent months growing into the ocean for external fertilisation. This happens in a mass event annually often affectionately named the world’s largest orgasm on the world’s largest organism.

It’s literally just an eruption that lasts for 20 minutes to a half an hour, where the whole Great Barrier Reef just has sex, with coral polyps releasing. Clams go. Sea cucumbers go. Starfish go. Everything just goes. It’s literally a mass orgy. It’s the biggest sexual event on the planet. It’s an amazing thing to go snorkelling or diving in.

Gareth Phillips, Marine Biologist

During this time the Great Barrier Reef is transformed into an underwater spectacle resembling the inside of a snowglobe. The spawn then produces a pinky-brown ‘slick’ on the surface where eventually, some sperm will meet a compatible egg and produce a larvae that takes about ten days to fully mature. It will swim around anywhere from two weeks to nearly two months until it finds somewhere to settle metamorphasizing into a coral polyp and beginning its journey building a coral colony by replicating itself.

When does it happen?

Coral spawning occurs in late spring or early summer

The 2018 mass spawning event is predicted to occur between November 26 and November 29.

Experts are able to predict probable times of coral spawning but there still remains an air of mystery around when it occurs. It only happens at night and once the water temperature is above 26ºC for the whole month prior and the seas are calmer. What actually triggers the event still remains unknown and tell-tale signs won’t reveal themselves until 20-30mins before it occurs.

The time of year depends on the reef location. Reefs off Cairns and Port Douglas generally begin spawning two to six nights after the full moon in November and it’s usually just the one night that it explodes however it may occur over different nights in late spring or early summer. It only happens at night once most plankton feeders are sleeping to give the eggs a greater chance at survival.

What happens if I miss it?

While any natural events are never a guarantee don’t let that dishearten you. The Great Barrier Reef transforms itself from day to night and is a completely different beast after the sun sets. Spend your time discovering the creatures that like to stay hidden during the day – and remember; you are diving or snorkelling the Great Barrier Reef at night, that in itself is a pretty special experience and an opportunity not many people have the chance to experience.

Ways to experience

Divers or snorkelers alike can both experience the spawning

Snorkelers jumping into the Great Barrier Reef for the spawning

Divers awaiting their time to dive the reef at night

Single night trips for the coral spawning depart both Cairns and Port Douglas over the predicted period. These leave late afternoon and return after midnight.

Depart Cairns
Tusa Dive – 26 and 27 November 2018
Divers Den – 28 and 29 November 2018

Depart Port Douglas
Divers Den – 27 November 2018

Liveaboards operate over the predicted dates however these are not dedicated coral spawning trips. Plans can vary depending on weather and time, so if you are interested in a liveaboard experience enquire directly with the company for their plans around the annual event.

Pro Dive Cairns

Mike Ball Dive Expeditions

Spirit of Freedom

Divers Den

Share your experience

Share you photos or videos

It’s important to share the good news stories that surround the reef to drive people to make positive changes to help the precious marine park. If you’re one of those fortunate enough to witness this year’s spawning, make sure to share your experience by:

  • Reporting  any coral spawning sightings via the Eye on the Reef app – this will also appear of the Citizens of the Great Barrier Reef Citizens Atlas
  • Upload your photos to social media using the hashtags #spawningGBR #exploreTNQ #citizensGBR #uniteforthereef

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While the coral spawning is incredible, the Great Barrier Reef is amazing every other day of the year.

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