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Richard Barnden

Palau Spawning Aggregations by Richard Barnden of Unique Adventures

Born on the south coast of England, Richard was always drawn to the ocean. After settling down in Palau, Richard found himself amazed by how fish were connected to the phases of the moon, and how it was possible to predict certain behaviors. For the last four years, Richard has been documenting spawning events, blackwater diving, and the reefs of Palau. Richard’s goal is to capture behavior in an artistic way.

In the mid 1970s Robert E. Johannes, a tropical marine ecologist came to the islands of Palau. Johannes pioneered the idea of integrating local knowledge from fishermen with Western concepts of fisheries management, and applying both directly to resource conservation.

Local knowledge of lunar cycles and spawning aggregations is invaluable for the protection of breeding grounds. This information would rarely be discovered without knowledge from local fishermen. Johannes’ pioneering work, with the help of local communities, went on to set up fishing ‘closures’ for particular species of fish around their spawning aggregation cycles. These are still in force today.

It isn’t only locally enforced policies that make Palau a unique and special place for spawning aggregations. Palau has Marine lakes, rock islands, mangroves and a large lagoon making it a perfect place for young juveniles to grow and survive away from the dangers of bigger reef dwelling predators. Surviving to adulthood, they too can join others in a massive spawning aggregation.

Palau’s regular southern lagoon dive sites are located in a relatively small area. There is no need to cover hundreds of miles on a live aboard trip! For dive guides, this has it’s advantages. Diving the same sites day in, day out, and month in, month allows one to familiarize themself with each location. Dive guides keep detailed logbooks, and having notice large aggregations of fish congregating on regular occasions. Patterns emerge, and can be used to build a database of spawning events that coincide with moon cycles each year.

Only a few dedicated dive shops have the knowledge of lunar cycles and tidal times to be able to practically guarantee such events.

Unique Dive Expeditions, a product of Sam’s Tours, offers educational expeditions targeting spawning aggregations. After spending the last five years studying these aggregations, three regular spawning events have been successfully observed. Other aggregations are being studied, but the challenges of spawning at night or beyond recreational diving limits make them logistically difficult to observe.

Each species of fish has its own spawning patterns, triggered by a specific lunar phase. Some species, such as the Twin spot snapper (Lutjanus bohar) and Bumphead parrotfish (Bolbometepon muricatum), will spawn every month. Others, like Blue lined sea bream (Symphorichthys spilurus), will only spawn once or twice each year.

The Blue Lined Sea Bream – (Symphorichthys spilurus)

During the months of March, April and May these strange but beautiful looking fish form one of Palau’s largest recorded spawning aggregations to date. A rarely seen fish on the reef, these normally solitary fish hide inside the lagoon or on deep sandy drop offs, feeding on crustaceans hidden in the sand.

As their spawning season approaches individuals start gathering in two main areas of Palau. This aggregation can reach up to 50,000 fish. Just seeing the size of the school when assembled can be more impressive than the actual spawning event itself!

When the correct formula of month, day, tide and time come together the sea bream are ready to spawn. The school moves from its aggregation area to a location with current that will carry their gametes to safety. From 60m to 15m the school becomes a tight mass of yellow fusion and the fish begin spawning. Bullsharks, Blacktip sharks and often lemon sharks are seen slowly swimming through the school waiting for a tired fish to pick off.

The Twin Spot Snapper – (Lutjanus bohar)

Also found in Peleliu and on other outer areas of Palau, these fish aggregate around full moon. Schooling in mid water during the day, this impressive school looks like a dark cloud as you approach it. Between 5,000 and 10,000 fish can be seen schooling and spawning here.

Entering just as the sun rises at one of Palau’s notoriously strong current dive sites, the reef is barely visible as the dark cloud of snappers appears in the distance. Bull sharks and blacktip sharks parade around the outskirts of the school. Suddenly the spawning erupts, and all hell breaks loose as multiple females shoot to the surface with males on the chase releasing their milky gametes into the water column.

Visibility goes from 30m to 3m near the surface and hungry black snappers are crazily feeding on the newly born youngsters. Divers drifting in the blue water doing their safety stops with the lucky snapper survivors you realize they have just witnessed one of natures magical moments.


The Bumphead Parrotfish – (Bolbometepon muricatum)

One of the most recent spawning aggregation discoveries is that of the Bumphead Parrotfish. Hidden on the West side of Palau lies a sandy slope perfect for the continuation of one of the ocean’s friendliest green giants.

Scientists and divers knew little about their reproductive behavior until Blue Marlin divers found the ground breaking site. This is the biggest bumphead aggregation discovered on the planet. Many divers are lucky to have witnessed a school of a hundred feeding around the reef, but ahere you can see more than a thousand! The bumpheads display color changes, males “bump” heads and a thousand fish join to spawn in an unforgettable event.

Early in the morning the school starts to form on the shallow reef top. One by one, following each other from the shallows out onto the reef like a waterfall, the aggregation begins to form. Hundreds turn into a thousand and the reef starts buzzing with exchitement.

When the correct combination of light and tide collides, so do the bumpheads. Each green fish now starts displaying sexual dimorphism (colour changes). Bands and bars start appearing on the bodies and all heads are now white.

The huge school spills into the blue water and the fish begin schooling deeper while swimming at a faster rate . The mating dance begins! Males and females swim backward and foreword in some kind of untimely dance, white heads bobbing around in the deeper bluish water.

When the first female to makes her move, the whole school will rise and a mass spawn will occur. Spawning for only a few intense minutes at first the school darts back into the deep and the mating dance continues, with the females seeming to make the males work a little harder.

Again another female breaks off from the huge school and rises closer to the surface, with eager males close behind. This firework procession can last more than thirty minutes. Eventually the school and spawning will slowly start to decrease as the tired bump heads begin to leave the site. A thousand dwindles down to less than a hundred and the reef returns to normal as all the bumpheads leave, ready to return again next month.

I feel privileged to be able to work and study these aggregations in a place like Palau, a country that has protected its very heritage and fish aggregations early on in an effort to preserve tradition and culture. Palau realizes the vulnerability and high importance to the oceans. Spawning aggregations are vital for the survival of fisheries and our oceans. The more we can learn about them, the more we can protect them.