New Paper on Vessel Noise Exposures of Harbour Seals in the Wadden Sea

SATURN partners at the Institute for Terrestrial and Aquatic Wildlife Research (ITAW), University of Veterinary Medicine Hannover and Aarhus University have published a new paper in the journal Scientific Reports. The paper, "Vessel noise exposures of harbour seals from the Wadden Sea” discusses how vessel noise exposure on seals in the Wadden Sea were quantified using DTAGs that record long-term sound and movement. An automated tool was developed to detect intervals of elevated noise in the sound recordings, which can now applied to new DTAG recordings from seals in the Elbe that have been collected over the past few years.

Seals in the Elbe River. Photo: ITAW TIHO.

Abstract

The North Sea faces intense ship traffic owing to increasing human activities at sea. As harbour seals (Phoca vitulina) are abundant top predators in the North Sea, it is hypothesised that they experience repeated, high-amplitude vessel exposures. Here, we test this hypothesis by quantifying vessel noise exposures from deployments of long-term sound and movement tags (DTAGs) on nine harbour seals from the Wadden Sea. An automated tool was developed to detect intervals of elevated noise in the sound recordings. An assessment by multiple raters was performed to classify the source as either vessels or other sounds. A total of 133 vessel passes were identified with received levels > 97 dB re 1µPa RMS in the 2 kHz decidecade band and with ambient noise > 6 dB below this detection threshold. Tagged seals spent most of their time within Marine Protected Areas (89 ± 13%, mean ± SD) and were exposed to high-amplitude vessel passes 4.3 ± 1.6 times per day. Only 32% of vessel passes were plausibly associated with an AIS-registered vessel. We conclude that seals in industrialized waters are exposed repeatedly to vessel noise, even in areas designated as protected, and that exposures are poorly predicted by AIS data.

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Citation

Nachtsheim, D.A., Johnson, M., Schaffeld, T., van Neer, A., Madsen, P.T., Findlay, C.R., Rojano-Doñate, L., Teilmann, J., Mikkelsen, L., Baltzer, J., Ruser, A., Siebert, U., & Schnitzler, J.G. (2023). Vessel noise exposures of harbour seals from the Wadden Sea. Scientific Reports 13.