Lone fish thriving amid coral decline

Nicholas McElroy

It's the fish species that's thriving amid bleached coral while almost every other species is in decline.

Populations of the beaked and brightly-coloured parrotfish increased up to eight times on damaged reefs, Australian Institute of Marine Science researchers say.

Not only are populations increasing on reefs hit by coral bleaching due to warmer oceans but the species of wrasse are also getting bigger by about 20 per cent than parrotfish on healthier reefs.

That's because they're feasting on the build up of "scunge" - a layer of microalgae and cyanobacteria that build up on the dead coral.

The findings came after researchers looked at fish populations at severely bleached areas of the Great Barrier Reef, off Queensland, and the Chagos Archipelago, in the middle of the Indian Ocean.

The researchers concluded that the coral and the parrotfish form a feedback loop which brought each other into balance.

When parrotfish move in and eat all the scunge it gives coral a better chance to recover.

And as reefs recover parrotfish numbers decline, according to the research led by Perth-based marine biologist Dr Brett Taylor.

Dr Taylor said warming oceans place enormous pressure on reefs.

The research is published in the journal Global Change Biology.