Dolphins at risk from noise

Posted: 4 May 2006

It is well known that dolphins are at risk from toxic pollution in the oceans and illegal fishing, but now a new danger has been identified: pile driving and industrial noise.

According to a research paper published in the CIWEM Water and Environment Journal, such noises can adversely affect dolphin behaviour, communication and breeding.

Bottlenose dolphins that reside in designated Special Areas of Conservation throughout the United Kingdom, including Dorset, Anglesey and Cornwall, are at significant risk from pile driving. The frequency range of pile driving noise can interfere with their ability to communicate, find food and avoid predators. This can affect their behaviour, health and their ability to breed successfully. Lactating females and young calves are particularly vulnerable, suffering from impaired hearing and temporary displacement.

Recently more than 600 dolphins died mysteriously off the Indian Ocean archipelago in Zanzibar. The phenomenon has created a stir among marine experts, with varying theories that the Indian Ocean Bottlenose dolphins may have been hurt by pollution or underwater noise.

Author, J.A. David, believes that mitigation measures must be put in place to help prevent such occurrences. Operations should be restricted to low tide and suspended during calving season, an exclusion zone should be monitored before any activity starts and marine work should cease if a dolphin enters the work area. Other innovative ideas include creating an air bubble curtain and creating a ramped warning signal to give dolphins time to leave the area before work commences.

J.A. David also calls for further research into the reactions of marine mammals to industrial noise to help mitigate future effects in relation to the increase in off-shore industry, such as the construction of wind farms.

The Water and Environment Journal is published quarterly by Blackwells for The Chartered Institution of Water and Environmental Management. It can be ordered online through CIWEM's website.