Year-round acoustic presence of sperm whales (Physeter macrocephalus) and baseline ambient ocean sound levels in the Greek Seas

Published: Apr 12, 2019
Sperm whale Physeter macrocephalus Passive Acoustic Monitoring year-round presence Hellenic Trench North Aegean Trough Passive Aquatic Listener East Mediterranean Greek Seas Ambient Sound Levels Delphinids

The sperm whale (Physeter macrocephalus) is the largest odontocete occurring in the Greek Seas. However, monitoring the
species’ spatiotemporal distribution patterns is especially difficult during the winter months when unfavorable weather conditions
often hinder survey efforts. In the Greek Seas, visual cetacean surveys are typically not conducted between November and March. In a first attempt to collect year-round baseline information on sperm whale occurrence patterns in Greek waters, two Passive Aquatic Listeners (PALs) were deployed for 19 months, at Pylos Station (36.8 N, 21.6ο E) in the Hellenic Trench, and at Athos Station (40.0 N, 24.7ο E) in the North Aegean Trough. Results revealed the year-round presence of sperm whales at Pylos Station with a higher number of detections observed during late spring and throughout the summer. No sperm whale vocalizations were detected at Athos Station. An ambient sound level analysis revealed higher winter and lower summer levels at both sites largely driven by local weather conditions. Results showed that marine life in the Hellenic Trench area was exposed to higher low frequency (< 1 kHz) sound levels (by up to 10 dB re 1 μPa2/Hz). Ambient noise below 1 kHz is frequently dominated by anthropogenic sources including shipping. Ship strikes and noise disturbance constitute major threats for the small, genetically isolated, endangered
sperm whale population. The results of this study are useful for sperm whale conservation efforts in the region and may help
policymakers in prioritizing mitigation measures, including the establishment of speed limits and rerouting of ship traffic.

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Author Biographies
NIKOLETTA DIOGOU, Department of Marine Sciences, University of the Aegean, University Hill, 81100 Mytilene Hellenic Centre for Marine Research, Anavissos, 19013

Department of Marine Sciences

PhD Candidate

HOLGER KLINCK, Bioacoustics Research Program, Cornell Lab of Ornithology, Cornell University, Ithaca, NY 14850

Bioacoustics Research Program

Cornell Lab of Ornithology

Director of the Bioacoustics Research Program

ALEXANDROS FRANTZIS, Pelagos Cetacean Research Institute, Vouliagmeni, 16671
Scientific Coordinator
JEFFREY A. NYSTUEN, Applied Physics Laboratory, University of Washington, Seattle, WA 98105-6698

Applied Physics Laboratory

Senior Principal Scientist

EVANGELOS PAPATHANASSIOU, Hellenic Centre for Marine Research, Anavissos, 19013

Research Director

Deputy Director of the Institute of Oceanography

STELIOS KATSANEVAKIS, Department of Marine Sciences, University of the Aegean, University Hill, 81100 Mytilene

Department of Marine Sciences

Associate Professor

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