3 Things You Should Know About Photographing Coral Spawning

Every year on the 23rd day of the third lunar month — the birthday of Mazu — another spectacular celebration unfolds beneath the waves off Taiwan's southern coast. The water column fills with a dreamy vision of pink dots drifting through the sea: this is coral spawning, one of the rarest and most magical events in the natural world. Some say the trigger is light; others point to water temperature, tidal range, or the phase of the moon — but none of these factors has been confirmed by researchers, so the exact timing of a spawning event remains impossible to predict with certainty.

Yet in the Kenting area, this once-unpredictable underwater spectacle lines up remarkably well with Mazu's birthday year after year. Word has spread, and the reputation of Kenting's coral spawning has attracted swarms of divers eager to test their luck and witness the great mass release firsthand.

Following the advice of experienced divers, we conducted three consecutive nights of night diving, choosing entry times of around 7

p.m., 8 p.m., and 9 p.m. based on tidal conditions. The brilliantly lit underwater world, seen from shore, resembled the famous blue tears of Matsu Island. On the surface just before entry, we found it blanketed with distinctly visible pink coral eggs; the spawning release itself could be observed at depths of just 30 cm to 2 m below the surface.

Coral eggs sit nestled inside the coral's polyp openings — like a pimple on the verge of popping — waiting for the current to carry them out in a burst. We therefore recommend that divers hire a dedicated dive guide from a local dive shop. Beyond the obvious safety benefit of having someone who knows the nighttime terrain, an experienced dive guide can help you identify which coral colonies are on the verge of releasing their eggs.

Synchronized Coral Spawning Is Actually a Survival Strategy

One theory holds that coral spawns at night because the water is cooler than during the day, and because moonlight plays a role in triggering the event. Another theory suggests that nighttime spawning reduces predation pressure, since many fish are sleeping and fewer predators are active — giving the gametes a better chance of surviving long enough to be fertilized. Although a mass coral spawning is effectively an all-you-can-eat buffet for predators, it is in fact a highly effective reproductive strategy: because coral cannot move freely, colonies across a reef synchronize and simultaneously release enormous quantities of eggs and sperm into the water at once, overwhelming predators and dramatically increasing the odds that some gametes will successfully fuse and survive.

For divers watching the spawning unfold underwater, it feels like a live-action feeding show — it's common to suddenly see a dense school of priacanthids sweep past at close range. This actually provides a reliable cue for underwater photographers: where the fish converge, a coral colony is likely releasing its gametes. Through macro photography, divers can observe coral in an entirely new light. The spawning colonies seen at the Nuclear Power Plant No. 3 outlet area at the Kenting National Park are mostly from the family Merulinidae; however, coral identification is an extremely complex process that requires photographs taken from multiple angles and in different states — a single image is never enough for a reliable identification.

"To identify coral species more accurately, start by photographing the entire colony, then move in for close-up shots of individual polyps and their openings. If tentacles or coenenchyme are covering the coral surface, gently wave your hand nearby to encourage the tentacles to retract. This allows you to record the coral's external features more completely. If you have a scale bar available, place it next to the coral — this will document the size of both the colony and the individual polyp openings, and will be a valuable aid for anyone attempting a species identification."

Around Mazu's Birthday Is Actually a Great Time to Have Babies

The underwater world at Kenting in the latter part of the third lunar month is buzzing with life. Beyond the dramatic coral spawning event, many other marine creatures also choose this period to release their gametes into the water. sea cucumbers preparing to spawn will arch the front half of their bodies upright and release white clouds of eggs and sperm. sea stars curve their five arms inward, lifting the central disc off the substrate so that water currents can carry their released gametes away — preventing self-fertilization. And Chondrocidaris brevispina, a wonderfully quirky sea urchin with a vivid yellow appearance, makes a rare appearance during this season as well, emerging to reproduce. The next time you go to watch coral spawning, take a moment to look around and observe the other remarkable behaviors happening nearby.

Chondrocidaris brevispina looks strikingly like a strawberry popsicle from a traditional Taiwanese ice shop, which is why we affectionately call it the "popsicle sea urchin." These creatures normally hide deep within reef crevices and are almost impossible to spot — but during coral spawning season, they crawl up to the highest points of the reef and participate in the mass spawning event alongside the coral, boosting their own fertilization success. So after you've finished photographing the coral spawning, don't rush back to shore to review your shots. Slow down, look carefully around the reef, and you just might discover one of these rare and mysterious little creatures.

What You Should Know When Photographing Coral Spawning

We are grateful to Chen Qi-En, Curriculum Director at Taiwan Dive, for sharing with us what you need to keep in mind when observing coral spawning. Since coral spawning takes place after dark, night diving is an absolute prerequisite. PADI (certification agency), SDI (certification agency), SSI (certification agency), and other agencies all offer dedicated night diving courses. These courses cover how to use a Flash Light to navigate and signal your direction underwater — and because verbal communication is impossible beneath the surface, knowing how to combine hand signals with Flash Light signals is especially important.

Beyond night diving as the "foundational" skill for observing coral spawning, what else do you need to pay attention to?

1. Maintain neutral buoyancy — do not stand on or touch the coral

Neutral buoyancy is a basic requirement for every diver. Stop using "I'm a beginner" or "I'm new to this" as an excuse to justify careless behavior. If you cannot maintain neutral buoyancy throughout an entire dive without touching the bottom, that means you need to go back to an instructor and review your fundamentals — let alone attempting to add a camera into the mix. Doing so not only increases your own risk, but also causes genuine ecological damage.

2. Coral spawning is happening everywhere — there's no need to rush or crowd

The coral spawning cycle in Kenting during Mazu's birthday period is quite predictable. When you see one coral colony begin to release its gametes, there are almost always other colonies nearby doing the same. Having too many divers congregate around a single coral creates poor compositions, jostling, and even conflict — and the concentrated blaze of lights from a large group of divers may interfere with the coral's natural spawning behavior.

3. Keep an eye on your dive buddy — don't let solo diving become the norm

We often joke that during coral spawning season, the outlet area at Kenting transforms into a night market — the underwater bay is packed with Flash Lights, blazing bright in every direction. But when you're deep in concentration shooting a frame, one moment of looking up can reveal that you've drifted away from your dive buddy, adding unnecessary risk to your dive.

Before entering the water, make sure you and your dive buddy have clearly agreed on the procedure for a buddy separation. Should you ascend to the surface and regroup if you lose each other, or should you try to return to a predetermined underwater meeting point and continue from there? Communicating this clearly before the dive is one of the most effective ways to reduce risk.

Cover image credit: Marco Chang Underwater Photography.

Further reading:

• 台灣潛水 | Taiwan Dive Center
• Underwater Photographer: Kyo Liu
• Underwater Photographer: Marco Chang Underwater Photography
• Soft Coral – Marine Habitat Micro-Guide
• Crustose Coralline Algae – Marine Habitat Micro-Guide