Sperm whale presence observed using passive acoustic monitoring from gliders of opportunity

Abstract

Habitat use by the endangered Mediterranean sperm whale subpopulation remains poorly understood, especially in winter. The sustained presence of oceanographic autonomous underwater vehicles in the area presents an opportunity to improve observation effort, enabling collection of valuable sperm whale distribution data, which may be crucial to their conservation. Passive acoustic monitoring loggers were deployed on vertically profiling oceanographic gliders surveying the north-western Mediterranean Sea during winter 2012-2013 and June 2014. Sperm whale echolocation ‘usual click’ trains, characteristic of foraging activity, were detected and classified from the recordings, providing information about the presence of sperm whales along the glider tracks. Widespread presence of sperm whales in the north-western Mediterranean Sea was confirmed. Winter observations suggest different foraging strategies between the Ligurian Sea, where mobile and scattered individuals forage at all times of day, and the Gulf of Lion, where larger aggregations target intense oceanographic features in the open ocean such as fronts and mixing events, with reduced acoustic presence at dawn. This study demonstrates the ability to successfully observe sperm whale behaviour from passive acoustic monitoring gliders. We identified possible mission design changes to optimize data collected from passive acoustic monitoring glider surveys and significantly improve sperm whale population monitoring and habitat use.

Arctic Marine Data Collection Using Oceanic Gliders: Providing Ecological Context to Cetacean Vocalizations

“…In marine mammal research, the deployment of Passive Acoustic Monitoring (PAM) sensors has been highlighted as one useful approach to overcoming the limitations of visual observations (Cauchy et al, 2020). Marine mammals, and particularly cetaceans, are challenging to survey, as they spend a large portion of their time vocalizing under water.…”

“…The potential for glider deployments with PAM systems allows for data collection through varying water masses and for long periods of time. More recently, such sensors have been integrated onto gliders that can measure presence, abundance, and distribution, of higher trophic level organisms, e.g., fish and cetaceans (Baumgartner and Fratantoni, 2008;Ferguson et al, 2010;Klinck et al, 2012;Meyer-Gutbrod et al, 2012;Baumgartner et al, 2013;Marques et al, 2013;Send et al, 2013;Suberg et al, 2014;Cauchy et al, 2020). However, only a few studies have focused on deployments with simultaneous measurements of physical and biological components using gliders (e.g., Suberg et al, 2014;Benoit-Bird et al, 2018), particularly in terms of monitoring higher trophic organisms such as cetaceans.…”

Gliders for passive acoustic monitoring of the oceanic environment

“…Multi-channel systems have been used to demonstrate the ability to track sperm whales (Kusel et al, 2017) and perform tactical maritime surveillance operations (Tesei et al, 2015). Autonomous PAM systems have been successfully attached on gliders, to observe soundscape variability along the glider's track (Wall et al, 2017), to map fish activity along cross-shelf transects in the Gulf of Mexico (Wall et al, 2012), to observe sperm whale populations in the Mediterranean Sea (Cauchy et al, 2020) and measure surface wind speed (Cauchy et al, 2018). They have been identified as suitable for long term acoustic population monitoring (Verfuss et al, 2019).…”

Streamlining analysis methods for large acoustic surveys using automatic detectors with operator validation

“…Gordon et al, 2020; Rone et al, 2014; Thode, 2004) or gliders (e.g. Bittencourt et al, 2018; Cauchy et al, 2020) can provide designed coverage of larger survey areas. Charter and running costs for dedicated vessels can become a major budgetary component for towed array surveys.…”