Dusky Dottyback by Christophe E Mirbach

The rate at which predators capture fish doubles when boats are motoring nearby, according to a study by the Universities of Exeter and Bristol.

An international research team found that noise from passing motorboats increases stress levels in young coral reef fish and reduces their ability to flee from predators. As a consequence they are captured more easily and their survival chances are halved.

One of the authors of the study, Dr Stephen Simpson of Exeter’s Biosciences department, said: “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.”

The team of scientists combined laboratory and field experiments, using playbacks and real boat noise, to test the impact of motorboat noise on the survival of young Ambon damselfish (Pomacentrus amboinensis) during encounters with their natural predator the dusky dottyback (Pseudochromis fuscus).

More than twice as many damselfish were consumed by the dottyback in field experiments at Lizard Island on the Great Barrier Reef when motorboats were passing.

Survival of damselfish on reefs with and without playback of boat noise.
Survival of damselfish on reefs with and without playback of boat noise.

There were over 12.5 million registered motorboats in the USA in 2013 and there are expected to be 0.5 million recreational motorboats using the Great Barrier Reef by 2040. Rather than being despondent though, the team is optimistic about the possibilities for management of noise and its potential impact.

“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. For example, we could create marine quiet zones or buffer zones, and avoid known sensitive areas or times of year when juveniles are abundant,” said Dr Simpson.

Previous research has shown that ship noise pollution slows European eels (Anguilla anguilla) and lets predators catch them twice as quickly.

Further Reading:
Anthropogenic noise increases fish mortality by predation by Stephen D. Simpson, Andrew N. Radford, Sophie L. Nedelec, Maud C. O. Ferrari, Douglas P. Chivers, Mark I. McCormick, Mark G. Meekan in Nature Communications