European sea bass (pictured) experience higher stress levels when exposed to the types of piling - a mechanical device used to drive poles into the ground - and drilling sounds made during the construction of offshore structures, researchers have found.
If you think noise pollution only stresses city slickers - think again.

European sea bass experience higher stress levels when exposed to the types of piling - a mechanical device used to drive poles into the ground - and drilling sounds made during the construction of offshore structures, researchers have found.

These fish also show signs of being confused when they encountered a potential predators while exposed to these underwater noises.

When researchers played recordings of piling sounds and mimicked an approaching predator, the sea bass made more turns and weren't able to move away from the predator.

The study, conducted by researchers based at Newcastle University, found that when exposed to drilling sounds, the sea bass actively avoided these areas, spending more time in an area that the researchers called the 'safe zone.'


Both the piling and drilling noises overlap with the hearing range of sea bass and many other species of fish, where sea bass hearing sensitivity is most acute at low frequencies of 100-1000Hz - coincident with many man-caused noises in water.
The sea bass also took longer to recover from exposure to the underwater sounds.

The impulsive nature of the piling noise triggered a reflexive startle response in the fish, which contrasted with the behavior elicited by the continuous drilling noise - fish exposed to the drilling noise recovered anti-predator behavior after thirty minutes exposure.

'Over the last few decades, the sea has become a very noisy place,' said Ilaria Spiga, a doctoral candidate at Newcastle University and the lead author of the study.

'The effects we saw were subtle changes, which may well have the potential to disrupt the seabass's ability to remain "in tune" with its environment.

'Sea bass, along with other bony fishes, rely on a characteristic "startle and response" mechanism to get away from predators.


The impulsive nature of the piling noise triggered a reflexive startle response in the fish, which contrasted with the behavior elicited by the continuous drilling noise - fish exposed to the drilling noise recovered anti-predator behavior after thirty minutes exposure.
'Exposure to underwater noises can make it harder for fishes to detect and react to predators.

'It could also impair their own ability to detect food.

'Man-made marine noise could potentially have an adverse effect on reproduction also.

'If fishes actively avoid areas where these sounds are present it could prevent them from entering spawning grounds, or affect communication between individuals.'

To conduct the study, the researchers played recordings of drilling from the English Channel, made during the installation of a new tidal barrage.

The sound of piling was taken from the construction of a new lifeboat station at Swansea Bay.

The piling sound was characterized by intense pulses of low frequency sound, whereas the drilling was continuous noise.

The researchers played back these noises on 54 sea bass sources from a commercial hatchery in France, and housed in a fiberglass holding tank.

To simulate a predator, the researchers used a spherical blue squash fixed to a clear pendulum arm moving through a 45-degree angle to a position next to the glass, but without contacting the tank.

The researchers found that fish under drilling and piling sound conditions showed reduced predator inspection behavior, and the noises also induced stress as measure by the fish's ventilation rate.

Both of these types of noises overlap with the hearing range of sea bass and many other species of fish, where sea bass hearing sensitivity is most acute at low frequencies of 100-1000Hz - coincident with many man-caused noises in water.

Offshore construction, shipping and even certain onshore activities can all add to ambient noise levels underwater.

While noise is recognized as a pollutant by the European Union's Marine Strategy Framework Directive (MSFD), only applications for larger or more complex project have to be registered with the UK government's Marine Noise Registry.

The researchers are calling for this to be expanded by proposing limits on the length of time that underwater drilling and piling can take place - or replacing piling with drilling, which has less of a sever effect than piling noises and can give fish time to recover from the physiological changes that these noises induce.