The World’s Largest Camouflage Grouper Spawning
Text and images by Alfonso Ribote
Males and females look for the right partner to spawn
French Polynesia is your typical island paradise of swaying palm trees and white sandy beaches located in the southeast Pacific Ocean and formed by five different archipelagos – Austral, Society, Gambier, Marquesas and Tuamotu. But divers go there for a different type of action that happens only once a year during a full moon – to witness the world’s largest aggregation of the camouflage grouper (Epinephelus polyphekadion) in Tetamanu Pass, Fakarava’s southern channel in the Tuamotu Archipelago. Fakarava has been designated a Biosphere Reserve by UNESCO.
AN ANNUAL AFFAIR
Between the end of June and the beginning of July, these groupers gather in phenomenal numbers in the channel, waiting for the right time to spawn. Scientists have estimated theaggregation to be between 15,000 and 18,000individuals. The fish gather at the mouth of the channel and wait at the bottom.
WAITING FOR THE RIGHT MOMENT
As the spawning day draws closer, the number of groupers increases so dramatically that they literally cover the entire bottom of the channel. The bellies of the females grow significantly to hold the eggs they will release into the water, and the territorial males fight for the most ideal positions, closest to the most fecund females, who look like they are about to explode.
FISHY ORGY
The right moment happens very early in the morning during the strong outgoing currents of the full moon. As the males change colour to a very light green, and the females have selected their mates, they rise from the bottom together, cheek-to-cheek, and release their load into the water. Many opportunistic males quickly follow after to join the party, creating a white haze of messy love scenes! The fertilised eggs are then carried by the currents, and are at the mercy of the open ocean.
FISH BUFFET
Tetamanu Pass is also known for having the highest population of grey reef sharks in the world – and the number blows up to an estimated 700 sharks during the grouper spawning. Other shark species like oceanic blacktips, lemons, silvertips and whitetip reef sharks are also present, though in much smaller numbers.They are the main predators of the groupers during the spawning. The sharks take advantage of this moment to have a good meal, as the groupers are more vulnerable –away from the shelter of the reef and solely focused on spawning their future offspring. Other groups of predators waiting for their chance to feed are the smaller fishes, which try and eat as many eggs as possible before they are swept out by the currents.
Once the partners are chosen, they slowly rise from the seabed together
LIFE CYCLE
When the fertilised eggs that make it to the open ocean hatch, the baby groupers grow very quickly to a certain size beforere turning to the reef to start the whole cycle again.
A COMMON SIGHT
The species is distributed in the Indo-Pacific, from the Red Sea, along East Africa, south to Mozambique, and east of French Polynesia. You can also find them in the western Pacific, from southern Japan to southern Queensland in Australia’s Great Barrier Reef. You can normally find them at depths of one to 60 metres. This species is only found in big numbers during its reproductive season when they migrate to the spawning areas. Its life span is about 30 years and it reaches sexual maturity at around four to five years.
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