Coral bleaching causing ‘unnecessary’ fish fights

Fish that have lost food due to mass coral bleaching are getting into more unnecessary fights, causing them to expend precious energy and potentially threatening their survival, new research said on Jan 3.

With the future of the world's coral reefs threatened by climate change, a team of researchers studied how a mass bleaching event affected 38 species of butterflyfish.

The colorfully patterned reef fish are the first to feel the effect of bleaching because they eat coral, so their "food source is hugely diminished really quickly", said Sally Keith, a marine ecologist at Britain's Lancaster University.

Keith and her colleagues had no idea a mass bleaching event was coming when they first studied the fish at 17 reefs off Japan, the Philippines, Indonesia and Christmas Island.

But when one of history's worst global bleaching events struck in 2016, it offered "the perfect opportunity" to study how it affected the fish's behavior, Keith told AFP.

The researchers returned within a year and were "shocked" to see the devastation of the once beautiful reefs, she said. Donning their snorkels or scuba gear, the team watched the fish "swimming around looking for food that just isn't there anymore," she added.

"There was a bit of crying in our masks."

The bleaching particularly affected Acropora coral, the main food source for the butterflyfish. That "changed the playing field of who's eating what," Keith said, putting different species of butterflyfish in increased competition for other types of coral.

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