Reef fish struggle to recognize competitors after coral bleaching

Some species of reef fish struggle to recognize their competitors after coral bleaching events, according to a new study led by Lancaster University. 

The research was focused on reefs across five Indo-Pacific regions. The experts analyzed the behavior of 38 species of butterflyfish before and after a coral bleaching event, based on more than 3,700 observations.

The researchers discovered that after the widespread loss of coral, butterflyfish were less capable of identifying threats and responding appropriately. This led the fish to make poor decisions and to engage in unnecessary fights. 

“By recognizing a competitor, individual fish can make decisions about whether to escalate, or retreat from, a contest – conserving valuable energy and avoiding injuries,” explained study lead author Dr. Sally Keith.

“These rules of engagement evolved for a particular playing field, but that field is changing. Repeated disturbances, such as bleaching events, alter the abundance and identity of corals – the food source of butterflyfish. It’s not yet clear whether these fish have the capacity to update their rule book fast enough to recalibrate their decisions.”

The experts report that after widespread coral losses, signaling between fish of different species was less common. Encounters led to chases 90 percent of the time after bleaching, and the distance of the chases increased substantially. This caused butterflyfish to spend much more energy chasing potential competitors than they would have done previously, noted the researchers.

“By looking at how behavior responds to real-life changes in the environment, and by seeing that those changes are the same regardless of location, we can start to predict how ecological communities might change into the future. These relatively small miscalculations in where to best invest energy could ultimately push them over the edge,” said Dr. Keith. 

According to the study authors, the findings may have implications for species survival as global warming increases the likelihood of coral loss.

The research was funded by the Natural Environment Research Council (NERC), the Australian Research Council, and the Villum Foundation.

The study is published in the journal Proceedings of the Royal Society B Biological Sciences.

Image Credit: Dr. Sally Keith

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By Chrissy Sexton, Earth.com Editor

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