According to new study released on Wednesday, fish that have lost food due to widespread coral bleaching are engaging in more pointless battles, which drains their energy and may endanger their survival.
January 5, 2023, 10:16 IST
According to new study released on Wednesday, fish that have lost food due to widespread coral bleaching are engaging in more pointless battles, which drains their energy and may endanger their survival.
Researchers looked examined how 38 species of butterflyfish were impacted by a huge bleaching event to better understand how climate change is threatening the future of the world's coral reefs.
The coral-eating reef fish are the first to experience the effects of bleaching because their "food source is drastically depleted pretty rapidly," according to Sally Keith, a marine scientist at Lancaster University in the United Kingdom.
When Keith and her colleagues initially saw the fish at 17 reefs off of Japan, the Philippines, Indonesia, and Christmas Island, they had no clue a massive bleaching event was about to occur.
But in 2016, when one of the greatest worldwide bleaching incidents in recorded history occurred, it provided "the perfect opportunity" to examine how it changed fish behaviour, according to Keith, speaking to AFP.
Within a year, the researchers went back and were "shocked" to find how the once-beautiful reefs had been destroyed.
The crew put on their dive or snorkelling equipment and observed the fish "swimming about hunting for food that just isn't there anymore," she continued.
"There was some sobbing going on behind our masks."
Combat failure
The primary food supply for butterflyfish, Acropora coral, was significantly impacted by the bleaching.
According to Keith, this "altered the playing field of who's eating what" and boosted competition between other butterflyfish species for other varieties of coral.
A butterflyfish will tip its down and raise its spiky dorsal fins to indicate to a rival that a specific piece of coral is theirs.
"It almost seems like your hackles are rising, "said Keith.
If that doesn't work, one fish will pursue the other until the other gives up, generally.
"I once tracked one for approximately 50 metres (165 feet), which was rather exhausting because they move so quickly, "added Keith.
3,700 butterflyfish interactions were recorded by the crew.
A variety of butterflyfish species used signalling to settle disagreements around 28% of the time prior to the coral bleaching disaster.
However, after bleaching, that percentage dropped to barely 10%, indicating numerous "unnecessary assaults," according to a recent study published in the journal Proceedings of the Royal Society B.
According to Keith, the study's primary author, "making bad judgements about who to fight, and where to put their very important energy, might be that little bit that tips them over the line towards genuine famine."
The researchers cautioned that it is unclear if the fish would be able to adjust to the alterations brought on by coral bleaching rapidly enough.
She said that it may possibly affect other animals and move up the food chain.
As the waters throughout the world warm due to human-caused climate change, global coral bleaching has been triggered.
Modeling studies conducted last year revealed that 99 percent of the world's coral reefs won't be able to recover even if the Paris climate target of limiting global warming to 1.5 degrees Celsius is met. At two degrees of warming, the percentage reached 100%.
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