Fish that have lost food due to global coral bleaching are engaging in more pointless battles, wasting vital energy and perhaps jeopardizing their existence, according to new research released Wednesday.

With climate change threatening the world's coral reefs, a team of researchers investigated how a huge bleaching event affected 38 species of butterflyfish.

Because the colorfully patterned reef fish eat coral, their "food source is dramatically decreased pretty quickly," according to Sally Keith, a marine researcher at Britain's Lancaster University.

When Keith and her colleagues originally researched the fish at 17 reefs near Japan, the Philippines, Indonesia, and Christmas Island, they had no notion a mass bleaching catastrophe was on the way.

However, when one of the worst global bleaching episodes in history occurred in 2016, it provided "the perfect chance" to examine how it altered the fish's behavior, Keith said as quoted by AFP.

She said the researchers returned after a year and were "shocked" to discover the ruin of the once-beautiful reefs.

The team, who were wearing snorkels or scuba gear, observed the fish "swimming around hunting for food that just isn't there anymore," she stressed.

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

It is worth noting that the bleaching had an especially negative impact on Acropora coral, which is the butterflyfish's primary food supply.

That "changed the playing field of who's eating what," Keith added, putting different species of butterflyfish in increased competition for other types of coral.

A butterflyfish will point its nose down and raise its spiny dorsal fins to indicate to a competition that a particular piece of coral is theirs.

"It's almost like raising your hackles," Keith said.

If that doesn't work, one fish will chase the other until the other gives up.

The researchers recorded 3,700 butterflyfish encounters.

As the world's oceans warm due to human-caused climate change, global coral bleaching has occurred.

According to a modeling study published last year, even if the Paris climate target of limiting global warming to 1.5 degrees Celsius is met, 99% of the world's coral reefs will be unable to recover. At two degrees of warming, the percentage increased to 100%.

Read more: Planet Earth Loses Half Its Coral Reefs since 1950