Prey fish captured by predators release chemical cues that act as a “distress call” to boost their chances for survival, a team of scientists suggests.

In a world-first study, researchers from Uppsala University in Sweden and James Cook University in Australia have found that fish harbour a chemical substance in their skin which is released upon injury. This sends out alarm cues that trigger fearful and escape behaviour in nearby fish.

For decades, scientists have debated the evolutionary origin of chemical alarm cues in fish, according to Dr. Oona Lönnstedt, the study’s lead author, a researcher in fish ecology from Uppsala University.

While the alarm cues provide obvious benefits to surrounding fish, it has been unclear whether the signals also help the sender, Lönnstedt says. In the current study, published in Proceedings of the Royal Society B, the researchers investigated what happens when chemical alarm cues of damselfish are released on the Great Barrier Reef.

The Swedish-Australian research team found that the chemical cue attracts additional predators to the capture site. While more predators would seem to mean more trouble, the study’s authors discovered that additional predators interfere with the initial predation event, allowing the prey a greater chance to escape.

During a series of laboratory trials, the team observed that additional predators attempted to pirate the prey, causing a commotion that gave the captured damselfish a chance to break free and hide. When another fish predator is attracted to the capture site, the prey will escape about 40 percent of the time, says the study’s co-author Professor Mark McCormick from the ARC Centre of Excellence for Coral Reef Studies at James Cook University.

“These findings are the first to demonstrate an evolutionary mechanism by which fish may benefit from the production and release of chemical alarm cues, and highlight the complex and important role chemical cues play in predator-prey interactions on coral reefs. It all goes to show that coral reef fish have evolved quite a range of clever strategies for survival which are deployed when a threatening situation demands,’ Lönnstedt notes.

The chemical alarm cues in fish seem to function in a similar way to the distress calls emitted by many birds and mammals following capture, McCormick says.

In a study published in 2013, researchers from the University of California researchers claimed that some birds sound an alarm to neighboring birds to alert them of a nearby predator and possibly incite a defensive mob attack against it. They also found that certain species of birds emit sounds to catch the predator’s attention, warning the foe that it has already been spotted.

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