Seals may experience hearing loss as a result of underwater vessel noise, according to new research from the University of St Andrews.
The study, led by ecologist Dr Esther Jones, has found that noise levels in UK shipping lanes can affect how seals and other marine mammals such as dolphins and whales find food and communicate with each other.
“Like humans living in busy, noisy cities, some seals live in areas where there is a lot of shipping traffic and associated noise,” said Dr Jones, who works at the university’s Centre for Research into Ecological & Environmental Modelling (CREEM).
“The UK has some of the busiest shipping lanes in the world, and underwater noise has been increasing over the last 30 years.”
The St Andrews team mapped the risk of exposure to this din for grey and harbour seals around the UK, and found that the level was high in 11 of 25 Special Areas of Conservation (SACs) associated with seals, particularly for declining harbour-seal populations.
“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 land,” said Dr Jones.
Using predictive acoustic models, the team observed 28 animals exposed to underwater noise generated by vessels in the Moray Firth in north-eastern Scotland.
For 20 of the animals the predicted noise levels were high enough to cause temporary hearing loss, although there was no evidence of a risk of permanent damage. The predictions were checked against sound-recorder measurements for accuracy.
High-resolution sound and movement tags are now being deployed to investigate the total noise exposure of individual seals, and their subsequent behaviour.
Dr Jones has suggested that chronic ocean noise “should be incorporated explicitly into marine spatial planning and management plans for existing Marine Protected Areas”.
The study, Seals and Shipping: Quantifying Population Risk and Individual Exposure to Vessel Noise, is published in the Journal of Applied Ecology here
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