Seals and shipping: quantifying population risk and individual exposure to vessel noise

• Published in: Journal of Applied Ecology
• Main Authors: Jones, Esther L., Hastie, Gordon D., Smout, Sophie, Onoufriou, Joseph, Merchant, Nathan D., Brookes, Kate L., Thompson, David
• Other Authors: González‐Suárez, Manuela, Scottish Government, Natural Environment Research Council
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2017
• Subjects: harbour seal
• Online Access: http://dx.doi.org/10.1111/1365-2664.12911; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2F1365-2664.12911; https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/1365-2664.12911

Summary Vessels can have acute and chronic impacts on marine species. The rate of increase in commercial shipping is accelerating, and there is a need to quantify and potentially manage the risk of these impacts. Usage maps characterising densities of grey and harbour seals and ships around the British Isles were used to produce risk maps of seal co‐occurrence with shipping traffic. Acoustic exposure to individual harbour seals was modelled in a study area using contemporaneous movement data from 28 animals fitted with UHF global positioning satellite telemetry tags and automatic identification system data from all ships during 2014 and 2015. Data from four acoustic recorders were used to validate sound exposure predictions. Across the British Isles, rates of co‐occurrence were highest within 50 km of the coast, close to seal haul‐outs. Areas identified with high risk of exposure included 11 Special Areas of Conservation (SAC; from a possible 25). Risk to harbour seal populations was highest, affecting half of all SACs associated with the species. Predicted cumulative sound exposure level, cSELs(M pw ), over all seals was 176·8 dB re 1 μPa 2 s (95% CI 163·3–190·4), ranging from 170·2 dB re 1μPa 2 s (95% CI 168·4–171·9) to 189·3 dB re 1 μPa 2 s (95% CI 172·6–206·0) for individuals. This represented an increase in 28·3 dB re 1 μPa 2 s over measured ambient noise. For 20 of 28 animals in the study, 95% CI for cSELs(M pw ) had upper bounds above levels known to induce temporary threshold shift. Predictions of broadband received sound pressure levels were underestimated on average by 0·7 dB re 1 μPa (±3·3). Synthesis and applications . We present a framework to allow shipping noise, an important marine anthropogenic stressor, to be explicitly incorporated into spatial planning. Potentially sensitive areas are identified through quantifying risk to marine species of exposure to shipping traffic, and individual noise exposure is predicted with associated uncertainty in an area with varying rates of co‐occurrence. The ...