Bleached coral makes adult fish bully juveniles into predators' mouths

Sydney, November 4 : A new study has found that small fish sheltering in bleached coral, are being bullied by bigger fish, who push them out into the open water, into the mouths of predators.

According to a report by ABC News, reef fish ecologist Associate Professor Mark McCormick of James Cook University in Townsville carried out the study.

“On healthy coral, size doesn’t make a difference to whether you live or die,” said McCormick, also of the Coral Reef Studies ARC Centre of Excellence.

“On bleached coral, and to some extent on dead coral, you’ve got a different situation. If you’re larger, you’re more likely to survive than if you’re smaller,” he added.

McCormick and colleagues took a close look at the impact of coral bleaching on damselfish, which are an important source of food for larger commercially fished species like coral trout.

The fish feed on plankton, not coral, and can survive in a variety of habitat other than live coral, according to McCormick and this means that the fish have the best chance of surviving coral bleaching.

In a set of experiments on Lizard Island on Australia’s Great Barrier Reef, McCormick studied what happened when a juvenile fish was paired with an adult on a patch of coral for six weeks.

A third of the coral patches used were alive, a third were bleached but still alive, and the rest were completely dead.

McCormick found that juvenile fish died four times faster on bleached coral than on live coral.

He said that in live coral, the juveniles and adults pack tightly together, all hiding in the shelter of the coral.

But, in bleached coral, the adult fish sit further out from the coral and are more aggressive towards the juveniles.

“They force the juveniles out and away from the shelter where the little fish become more vulnerable to predators,” said McCormick.

“On bleached coral, it’s every fish for themselves and death rates are much higher among the runts,” he added.

According to McCormick, the research will improve scientists’ understanding of the impact on coral bleaching on fish populations.

--ANI