Food loss from mass coral die-offs is leading to ‘unnecessary’ fighting between fish, a new study suggests, which could lead to species extinctions. The competition for food robs the animals of valuable energy and possibly endangers their survival, according to reports published in the specialist journal “Proceedings of the Royal Society B‘ according to published research.
The researchers studied how coral bleaching affects 38 species of butterflyfish and observed the animals before and after the bleaching.
The rise in sea temperature as a result of global warming is leading to coral bleaching. Butterflyfish feed on corals, among other things. As a result, the fish’s food source is rapidly declining, Sally Keith, a marine biologist at Britain’s Lancaster University and lead author of the study, told AFP.
Too much competition for little
According to them, Acropora corals, the main food source for butterfly fish, were particularly affected by the bleaching. This has changed the situation when searching for food and has brought the different species of butterfly fish into increased competition for other coral species.
Misjudgments about who to fight and when to invest their most valuable energy could spell the difference in their ultimate starvation.
Sally Keith, marine biologist at Lancaster University, UK
The scientists were “shocked” by the condition of the coral reefs after the bleaching: The fish swam around looking for food that “just wasn’t there anymore,” Keith said. “We cried into our diving masks,” she said.
The researchers observed around 3700 interactions between butterflyfish. When a butterflyfish wants to signal to another that a piece of coral belongs to it, it points its nose down and raises its dorsal fin. “It’s almost like raising the hairs on the back of your neck,” Keith described.
Chase over 50 meters
If that’s not enough to drive away the competitor, one fish will chase the other until it gives up – sometimes over a long distance. “I chased one for 50 meters once, it was pretty tough, they’re very fast,” said Keith.
Before coral bleaching, different species of butterfly fish could use their signals to resolve around 28 percent of disputes. After bleaching, the proportion dropped to ten percent. According to the study, this points to many “unnecessary attacks”.
“Misjudgments about who to fight and when to invest their most valuable energy could be the deciding factor in whether they ultimately starve,” Keith said of the butterflyfish. According to the scientists, it is unclear whether the fish can adapt quickly enough to the changes triggered by coral bleaching.
Last year, model calculations on climate change showed that 99 percent of the world’s coral reefs would not be able to recover, even if the Paris climate agreement were complied with, which stipulates that global warming should be limited to 1.5 degrees compared to the pre-industrial age. With global warming of two degrees, it would even be 100 percent. (AFP)
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