Shipping noise ‘may cause hearing loss’ in seals
Harbour seals are declining in some regions of the UK, yet half of the SACs associated with them had a high risk of exposure to shipping.
Seals may experience temporary hearing loss from underwater vessel noise, according to new research by the University of St Andrews.
Ecologists developed maps to show the risk of exposure to vessel noise among the UK’s grey and harbour seals. They found that 11 out of 25 Special Areas of Conservation (SACs) had a high risk of overlap between seals and shipping.
The findings are particularly significant to harbour seals, according to a paper published in the Journal of Applied Ecology. Harbour seals are declining in some regions of the UK, yet half of the SACs associated with them had a high risk of exposure to shipping.
Lead author Dr Esther Jones said: “Exposure risk was highest within 50km of the coast, and any impacts will have the greatest effect on harbour seals as they generally stay close to the land.”
The team also investigated the underwater noise levels that individual animals are exposed to in the Moray Firth on the north east coast of Scotland. For 20 out of the 28 animals they observed, predicted noise levels were high enough to cause temporary hearing loss, termed temporary threshold shift (TTS).
Dr Jones said the noise can affect how sea mammals such as whales, dolphins and seals find food and communicate with one another.
“Urbanisation of the marine environment is inevitably going to continue, so chronic ocean noise should be incorporated explicitly into marine spatial planning and management plans for existing marine protected areas,” she explained.
Researchers are now deploying high resolution sound and movement tags to explore the total noise exposure of individual seals and their subsequent behaviour.
Dr Jones added: “We now need to begin assessing any behavioural changes of seals as a result of chronic exposure to underwater noise, so that we can understand the implications of those changes on individuals and ultimately on population dynamics.”
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