[MARMAM] Two New Publications on Sperm Whale Acoustic Ecology in the Offshore Gulf of Alaska

Niki Diogou niki.diogou at gmail.com
Wed Aug 21 15:56:36 PDT 2019

Dear all,

My colleagues and I are happy to share with the MARMAM Community our
two companion papers on
*Sperm whale (Physeter macrocephalus) acoustic ecology at Ocean
Station PAPA in the Gulf of Alaska*, published online in Deep Sea
Research Part I

*- Part 1 investigates the seasonality in sperm whale occurrences*

*Sperm whale (Physeter macrocephalus) acoustic ecology at Ocean
Station PAPA in the Gulf of Alaska – Part 1:  Detectability and

doi: https://doi.org/10.1016/j.dsr.2019.05.007


Sperm whales *Physeter macrocephalus* produce loud, stereotypical
click sequences and are an ideal species to be studied with passive
acoustic techniques.
To increase our limited knowledge of sperm whale occurrence patterns
in remote and inaccessible locations of the North Pacific, we analyzed
a five-year-long
(June 2007–April 2012) acoustic data set recorded at Ocean Station
PAPA (OSP; 50°N, 145°W) in the Gulf of Alaska (GOA). Firstly, we
assessed the sperm whale
 detection performance of the Passive Aquatic Listener (PAL), and
secondly, we investigated temporal patterns of sperm whale presence at
OSP. The PAL proved
 highly efficient, with above 50% probability of detecting more than
two sperm whales, a condition met for over 50% of the recordings.
Results indicated that
sperm whale clicks were recorded year-round, with a clear seasonal
pattern. The number of detections during the summer months was
approximately 70%
higher compared to winter. An ambient noise analysis showed that
differences in detection rates were likely not driven by seasonal
changes in ambient noise
levels. The average propagation range of sperm whale clicks ranged
between 7 and 8 km between summer and winter, with slightly decreased
detection distances
observed in winter. Seasonal shifts in the intensity of the Alaska
Current and the latitudinal oscillations of the North Pacific
Transition Zone results in changes in
water mixing, transport of nutrients and the concentration of prey
such as squid, which likely drives sperm whale distribution.

The manuscript is available for download at:


*- Part 2 assesses and explains the sperm whale oceanographic preferences *

*Sperm whale (Physeter macrocephalus) acoustic ecology at Ocean
Station PAPA in the Gulf of Alaska – Part 2: Oceanographic drivers of
interannual variability*.

doi: *https://doi.org/10.1016/j.dsr.2019.05.004


Understanding top predator responses to environmental variability is
key to assessing potential impacts of global warming on marine
ecosystems. However,
tracking environmental changes and their effects across multiple
trophic levels up to predators can be difficult. Here, we related the
interannual (2007–2012)
acoustic occurrence of sperm whales (*Physeter macrocephalus*) at
Ocean Station PAPA (OSP), in the offshore Gulf of Alaska (GOA), to
environmental drivers
within an explicit time-series modeling framework. In a model based on
a combination of *in-situ* and remotely sensed variables, ocean heat
content (HC),
meridional current (V), eddy kinetic energy (EKE), strength of the
permanent pycnocline (maxBVF), sea surface temperature (SST) and SST
standard deviation (SSTsd)
 explained 51% of the variability in sperm whale presence, indicating
a positive relationship between sperm whale occurrence and increased
ocean heating,
vertical stratification, and circulation. Sperm whale detections were
anomalously high in summer 2010 and winter 2011, and anomalously low
at the end of
summer and winter 2008, and spring 2011. Results suggest these
strongly anomalous detection events reflect a response to El
Niño–Southern Oscillation (ENSO)
events, with an 8-month lag. In the study area, El Niño leads to a
stronger permanent pycnocline, a weakening of the Alaska Gyre, a
northward expansion of the
North Pacific Subarctic Frontal Zone, and a prevalence of offshore
mesoscale eddies, likely favoring the abundance of squid and their
predator, the sperm whale.
The overall results are consistent with a scenario of increasing sperm
whale occurrence at high latitudes under increased ocean warming.

The manuscript is available for download at:


Please do not hesitate to contact me (niki.diogou
<https://lists.uvic.ca/mailman/listinfo/marmam> at gmail.com) with any
comments or questions.



Niki Diogou, PhD

*Acoustic Ecology*

University of the Aegean, Department of Marine Sciences
Oregon State University Research Collective for Applied Acoustics (ORCAA)
Hellenic Center for Marine Research, Department of Oceanography
*+593 996084868*
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