Two University of Saskatchewan biologists have discovered how motor boat noises make some reef fish easier prey.

"It's certainly not good to be near a boat if you're a small fish," said Doug Chivers, a University of Saskatchewan biology professor.

"The predator has a great advantage being able to capture the prey and if you are a little fish, you shouldn't be anywhere near a motor boat."

Chivers and Associate Professor of Veterinary Biomedical Sciences Maud Ferrari, along with colleagues from Australia and the United Kingdom, focused their study on the ambon damselfish and its natural predator, the dusky dottyback.

Doug Chivers

Doug Chivers was a part of an international research team that studied how motor boat noises affect reef fish. (Submitted by Doug Chivers)

The international research team simulated predator attacks in a tank and at field sites at the Lizard Island Research Station off the coast of Cairns, Australia.

Team members used high speed cameras to capture the damselfish's behaviour, to see how long it took for the fish to escape its predator.

The noise makes the damselfish more than two and a half times more likely to be eaten by predators.

They found that when the sound of a motorboat was around, the damselfish were six times less likely to be startled by the predator. They were also slower for getting out of the way and allowed the predator to get 30 per cent closer before they fled.

"It's overwhelming their cognitive ability. Imagine sort of having a jackhammer near you after a while or hearing a loud rock concert. It overwhelms your senses in the terms of being able to sense the rest of your world," said Chivers.

'Boat noise is something that could be quite stressful to fish. It's one of those ones that could be quite easy to manage.' - Doug Chivers, U of S professor of biology

He says the predator fish might not be affected by the boat sound in the same way because of its larger size and experience around the noise.

Chivers has been studying fish on the Great Barrier Reef for a number of years, looking at how humans have impacted the environment through other aspects such as ocean acidification and increasing temperature. 

"Boat noise is something that could be quite stressful to fish," he said. "It's one of those ones that could be quite easy to manage."

He says there could be designated no noise zones near fish habitats, or boaters could use quieter motors, like a four stroke engine.

Damselfish

Damselfish were the main focus of the international study. (Oona Lönnstedt)

"For somebody with a boat in Saskatchewan, it could be fantastic. You could go to the store and say 'I'd like to have a much more environmentally-friendly motor," said Chivers.

Chivers and his colleague Maud Ferrari plan on doing a similar study in Saskatchewan to see how motor boat noises affect fish in freshwater rivers and lakes.