Mass of spawning fish make a milky way on a coral reef

IT’S a game of life. A mass of fish dart in and out of a cloud of sperm and eggs off the island of Palau in the western Pacific, creating the next generation.

“The existence of red snapper spawning aggregations in Palau has been known for some time, so I wondered why there weren’t many photographs of it,” says photographer Tony Wu. Once he got in the water with them he discovered one possible reason – the fish were really fast and he struggled to keep up.

Spawning aggregations are common but not well understood. Two spot red snapper (Lutjanus bohar) gather in huge numbers where the edge of the reef meets the open ocean. They produce vast clouds of sperm and eggs – enough that plenty get fertilised, despite predators devouring much of the nutritious mixture. A strong current pulls any surviving fertilised eggs out to sea where they grow into adults. Some will make it back to the reef and spawn themselves, starting the whole process all over again.

Those same strong currents also made it difficult to get the shot, says Wu. “Getting into the right place at the right time was a challenge. The flow of water over the reef was steady and unrelenting, but I was able to position myself so that the action came to me.”

The spawning took place at Shark City diving site, and Wu spotted a few blacktip sharks lurking on the lookout for an easy meal.