Motorboat Noise Stresses Young Fish, Giving Predators Advantage

Noise from passing motorboats may give predators a deadly advantage in catching young fish. But researchers from the ARC Centre of Excellence for Coral Reef Studies at James Cook University, suggest there is an easy solution to the problem: Make less noise.

For their experiment, researchers used playbacks and real boat sounds to test the impact of motorboat noise on the survival of young Ambon damselfish during encounters with their natural predator, the dusky dottyback. Ultimately, researchers found that the deafening noise puts damselfish in a near perpetual stressed state that interferes with their startle reflex when predators are nearby. Stressed fish, the study showed, are more easily captured fish. In fact, the rate at which damselfish are captured can double when boats are motoring nearby, according to the university's news release.

"It [the study] shows that juvenile fish become distracted and stressed when exposed to motorboat noise and predators capitalize on their indecision," Professor Mark McCormick, one of the study researchers, said in the release.

"We found that when real boats were motoring near to young damselfish in open water, they became stressed and were six times less likely to startle to simulated predator attacks compared to fish tested without boats nearby," Dr. Stephen Simpson, lead author from the University of Exeter, added.

The team hopes their findings, recently published in the journal Nature Communications, will inspire better environmental noise management in coastal areas.

"If you go to the Great Barrier Reef, there is a lot of noise from motorboats in some places. But unlike many pollutants we can more easily control noise. We can choose when and where we make it, and with new technologies, we can make less noise," Professor McCormick said. "For example, we could create marine quiet zones or buffer zones, and avoid known sensitive areas or times of year when juveniles are abundant."

While climate change may seem like a much larger threat, reducing local noise pollution will help reef communities build a greater resilience to looming threats such as global warming and ocean acidification, researchers concluded.

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