Dear MARMAM community,

On behalf of my co-authors, I'm happy to announce that our paper "Acoustic
occurrence of deep-diving cetaceans in the southern Adriatic Sea" has been
published in Marine Mammal Science.

Constaratas, A. N., Holcer, D., Özgöbek, Ö., & Širović, A. (2024). Acoustic
occurrence of deep-diving cetaceans in the southern Adriatic Sea. Marine
Mammal Science, e13204. https://doi.org/10.1111/mms.13204

Abstract:
Goose-beaked whale (Ziphius cavirostris) and sperm whale (Physeter
macrocephalus) are two deep-diving odontocete species known to occur in the
southern Adriatic Sea, based on intermittent stranding and sighting data.
To get a better understanding of their presence in this region, we studied
the occurrence of echolocation clicks produced by these species in passive
acoustic recordings. Passive acoustic data were collected offshore
Dubrovnik, Croatia. Data were collected from October 2018 to December 2019
and from June 2020 to December 2020 using a High-frequency Acoustic
Recording Package (HARP) deployed at approximately 1,000 m depth. To
determine the occurrence of echolocation clicks, a two-step process was
used: automated detection followed by manual annotation of the detected
clicks. Automated detection was implemented using a low signal-to-noise
ratio threshold and a broad range of parameters to detect as many clicks as
possible. Two click clustering algorithms were evaluated for performance on
this data set: an unsupervised clustering algorithm and a filtering
algorithm. The performance of the algorithms was compared to the manual
annotations to determine a time-effective method for future monitoring.
Both species were found to be acoustically active in the southern Adriatic
Sea. Goose-beaked whales were detected throughout the recording period,
with echolocation clicks peaking during the winter of 2018–2019 and in the
spring of 2019. Conversely, sperm whales were more acoustically active
during short, irregular windows, mostly during the summer of 2019. These
results suggest that goose-beaked whales are residents, and, due to the
irregularity of their detection, sperm whales are likely occasional
visitors to this region. The unsupervised clustering algorithm performed
better than the tested filtering algorithm, with F-scores of 0.74 and 0.46,
respectively. This study provides knowledge that can help with effective
conservation efforts and further contribute to our understanding of
cetacean occurrence in the region.

Feel free to contact me at <alexandra.constara...@ntnu.no> for questions.

Best,

Alexandra Constaratas

PhD candidate
Trondhjem Biological Station, Department of Biology
Norwegian University of Science and Technology (NTNU)
N-7491 Trondheim, Norway
email: alexandra.constara...@ntnu.no
https://www.ntnu.edu/biology/research/mbel
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