Underwater Noise Pollution Keeps Fish from Finding Home

Noise pollution in the ocean may prevent fish from finding home, according to new research on reef-dwelling fish in French Polynesia by the Universities of Bristol, Exeter and Liège

Fish normally make use of acoustic cues from other fish and invertebrate reef residents to locate suitable habitats, but the researchers found that fish appear to have a more difficult time finding home when boat noise is present.

"Natural underwater sound is used by many animals to find suitable habitat, and traffic noise is one of the most widespread pollutants. If settlement is disrupted by boat traffic, the resilience of habitats like reefs could be affected," said research co-author Sophie Hilles, a PhD candidate at the University of Bristol.

Coral reefs are naturally noisy places, full of thriving invertebrates that each generate their own acoustic identifiers in the form of feeding and territorial sounds. Waves, wind and currents also create background noise.

Motorboats are present along virtually every coastline where humans live, and the noise they make travels better underwater than through the air.

"Boat noise may scare fish, affecting their ecology," said study co-author Steve Simpson, a marine biologist at the University of Exeter. "Since one in five people in the world rely on fish as their major source of protein, regulating traffic noise in important [fishery] areas could help marine communities and the people that depend on them."

For their experiment, the researchers used fish larvae of an age where they would naturally be inclined to settle around a coral reef. Placed in a long plastic tube with a monitor on one end, the larvae were able to decide which end of the tube to swim towards. When the monitor played only ambient reef noise - a comfortable sign of home - an equal number of fish larvae were found at either end of the tube. But when boat noise was played on top of the ambient reef noise the larvae demonstrated s tendency to swim away from the noise.

"This is the first indication that noise pollution can affect orientation behavior during the critical settlement stage," said co-author Andy Radford, of the University of Bristol. "Growing evidence for the impact of noise on fish suggests that consideration should be given to the regulation of human activities in protected areas."

The research is published in the journal Marine Ecology Process Series.