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Coral Spawning on WA’s Midwest Coast

  • Writer: Danny Petrie
    Danny Petrie
  • 7 days ago
  • 3 min read

Where Science Meets Wonder on the Geraldton Sea

The ocean has been stretching its warm arms around Geraldton these last few weeks - slow southerlies, longer days, a November moon swollen with anticipation. Out beyond the horizon, where the reefs of the Houtman Abrolhos scatter like dropped pearls, the corals are preparing for their quiet, annual release of life.

This is coral spawning season.A brief window when the reefs breathe hope into the water.

It’s one of the great natural mysteries of Western Australia’s mid-west coast - rarely filmed, rarely spoken about, but profoundly alive.

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What Happens During Coral Spawning?

Corals don’t just grow; they perform. Once each year, they coordinate a mass release of egg-sperm bundles into the sea. Millions of tiny, pastel beads rising all at once, catching currents, drifting upward like a galaxy in reverse.

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The Science Behind the Magic

  • Corals synchronise spawning to the full moon, water temperature, and the easing of seasonal winds.

  • Bundles float upward, break apart, fertilise, drift as larvae, and - with luck - form new coral colonies.

  • This event is crucial for reef renewal and long-term resilience.


Learn more:Great Barrier Reef Foundation — What is coral spawning?https://www.barrierreef.org/news/explainers/what-is-coral-spawning

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Why the Midwest Coast Is So Unique

Here, 80 km off Geraldton, the Abrolhos Islands sit at one of the most southern limits for coral reefs in the Indian Ocean. They exist only because the Leeuwin Current brings warm tropical water down the coast, allowing coral species to thrive where they shouldn’t, by latitude alone.

A Temperate-Tropical Hybrid

  • Tropical coral species mix with temperate fish communities.

  • Spawning happens in both spring and autumn, unlike many tropical reefs.

  • Local observations show some species ripening by the November full moon, especially around East Wallabi and the Easter Group.

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Source:Gilmour et al. — Coral reproduction in Western Australiahttps://pmc.ncbi.nlm.nih.gov/articles/PMC4878369/

Hydnophora rigida reproductive timinghttps://en.wikipedia.org/wiki/Hydnophora_rigida


🌕 Late November 2025: What’s Happening Right Now?

We’re inside one of the strongest probability windows for spawning on the mid-west coast.

As of late November 2025:

  • Water temperatures have warmed steadily.

  • Winds have eased - crucial for near-surface fertilisation.

  • The recent full moon has set off the ecological “clock”.

Divers across WA often record mild to moderate spawning activity during this period, especially in sheltered reef pockets.

Spawning may unfold 1-6 nights after the full moon, just after sunset.


Signs You Can Look For

Underwater

  • Clouds of eggs and sperm drifting upward

  • Pink-white bundles shimmering in torchlight

  • Fish feeding frantically on the nutrient surge

Surface

  • Milky, pastel slicks at dawn

  • A distinctive sweet-ocean scent (the “spawning perfume”)

Even if you never see it directly, the sea tells stories if you meet it halfway.

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💚 Why This Matters (Especially This Year)

Western Australia’s reefs are still recovering from recent marine heatwaves - events that bleached corals across more than 1,500 km of coastline.

Every successful spawning season is a small resilience miracle.

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Spawning means hope.It means the reef is still trying — still reaching — still capable of renewal.


How to Witness It (Ethically & Locally)

Where to Go Near Geraldton

  • Eco Abrolhos (liveaboard trips in peak season)

  • Abrolhos Adventures (snorkel tours)

  • Offshore Charters WA

  • Local freediving/snorkel groups who often share real-time sightings


Best Conditions

  • Calm evenings

  • 1-6 nights after the full moon

  • Shallow reef areas with clear water


Eco-Friendly Practices

  • No touching or standing on coral

  • Reef-safe sunscreen

  • Use existing moorings

  • Keep lights low and movements gentle


Midwest Eco Stories always encourages responsible, low-impact ocean activity. Our reefs are living elders — treat them with the same respect.


A Midwest Eco Stories Closing Reflection

Some evenings, when the sea steadies and the moon floats up like a lantern, the reefs beneath Geraldton loosen their grip and let go - sending a cloud of future possibilities into the dark. Coral spawning is quiet work. Tender work. The kind that never makes a sound but fills the water with hope. Here on the mid-west coast, it reminds us that the ocean is still becoming, still healing, still dreaming forward - just as we are.

 
 
 

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