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ESR 52:163-176 (2023)  -  DOI:

Summer and winter surveys of deep waters of the Hellenic Trench, Greece, provide insights into the spatial and temporal distribution of odontocetes

Kirsten F. Thompson1,2,*,#, Thomas Webber1,#, Leonidas Karantzas3, Jonathan Gordon4, Alexandros Frantzis5

1Biosciences, University of Exeter, Devon EX4 4PS, UK
2Greenpeace Research Laboratories, University of Exeter, Devon EX4 4RN, UK
3Greenpeace Greece, 78 Kolonou Str, Athens, GR 10437, Greece
4Marine Ecological Research, Newport on Tay, Fife DD6 8JH, UK
5Pelagos Cetacean Research Institute, Terpsichoris 21, 16671 Vouliagmeni, Greece
*Corresponding author:
#These authors contributed equally to this paper

ABSTRACT: The Mediterranean Sea provides habitat for globally threatened cetaceans. The Hellenic Trench is an Important Marine Mammal Area, providing core habitat for sperm whales Physeter macrocephalus and Cuvier’s beaked whales Ziphius cavirostris. Surveys have characterized distributions of these species in near-shore areas (<2000 m deep). Sparse survey effort in deeper waters during winter has allowed speculation that it is not an important habitat in winter. We used passive acoustic monitoring from towed arrays to document cetaceans during summer and winter, covering 18366 km of trackline off the Peloponnese and Crete. We confirmed the acoustic presence of 5 odontocetes: sperm whales (n = 49 encounters; mean depth (x̄): 3360 m; range (R): 1250 to 4210 m), Cuvier’s beaked whales (n = 4; x̄: 3070 m; R: 1970 to 3770 m), Risso’s dolphins Grampus griseus (n = 5; x̄: 3340 m; R: 2250 to 4440 m), striped dolphins Stenella coeruleoalba (n = 2; x̄: 2980 m; R: 2490 to 3470 m) and rough-toothed dolphins Steno bredanensis (n = 1; 3650 m). We also encountered 224 unidentified delphinids, including a potential blackfish (3020 m). We confirmed that these species are present in the Hellenic Trench throughout the year. Given the impact of multiple threats on sperm and Cuvier’s beaked whales in the Hellenic Trench, we suggest that policymakers follow the precautionary approach in managing human activities in the area. Ongoing seismic surveys, hydrocarbon extraction and uncontrolled shipping could have potentially negative effects on these species at the population level and we advise caution in permitting such activities in future

KEY WORDS:DS: Physeter macrocephalus · Ziphius cavirostris · Passive acoustic monitoring · Mediterranean · Cetaceans · Oil and gas impacts

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Cite this article as: Thompson KF, Webber T, Karantzas L, Gordon J, Frantzis A (2023) Summer and winter surveys of deep waters of the Hellenic Trench, Greece, provide insights into the spatial and temporal distribution of odontocetes. Endang Species Res 52:163-176.

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