Fish biophony in a Mediterranean submarine canyon

Abstract

Although several bioacoustics investigations have shed light on the acoustic communication of Mediterranean fish species, the occurrence of fish sounds has never been reported below À40 m depth. This study assessed the occurrence of fish sounds at greater depths by monitoring the soundscape of a Mediterranean submarine canyon (Calvi, France) thanks to a combination of Static Acoustic Monitoring (three stations, from À125 to À150 m depth, 3 km from coastline) and of hydrophone-integrated gliders (Mobile Acoustic Monitoring; from À60 to À900 m depth, 3-6 km from coastline). Biological sounds were detected in 38% of the audio files; ten sound types (for a total of more than 9.000 sounds) with characteristics corresponding to those emitted by vocal species, or known as produced by fish activities, were found. For one of these sound types, emitter identity was inferred at the genus level (Ophidion sp.). An increase of from 10 to 15 dB re 1 lPa in sea ambient noise was observed during daytime hours due to boat traffic, potentially implying an important daytime masking effect. This study shows that monitoring the underwater soundscape of Mediterranean submarine canyons can provide holistic information needed to better understand the state and the dynamics of these heterogeneous, highly diverse environments.

The unexploited potential of listening to deep‐sea fish

“…Gliders allow the collection of ocean parameters over large temporal and spatial scales; the absence of a drive motor and propellers minimizes their mechanical noise supporting this device as an excellent platform for hydrophones (Bolgan et al, 2020;Lembke, Lowerre-Barbieri, Mann, & Taylor, 2018;Wall et al, 2013Wall et al, , 2017.…”

“…Gliders allow the collection of ocean parameters over large temporal and spatial scales; the absence of a drive motor and propellers minimizes their mechanical noise supporting this device as an excellent platform for hydrophones (Bolgan et al., 2020; Lembke, Lowerre‐Barbieri, Mann, & Taylor, 2018; Wall et al., 2013, 2017). Despite their high potential as mobile 3D acoustic sensors, only five studies have applied PAM of fish populations to glider technology to date (Bolgan et al., 2020; Lembke et al., 2018; Wall, Lembke, & Mann, 2012; Wall et al., 2013, 2017). In addition to sounds emitted by groupers, toadfish and cusk‐eels, more than a dozen unknown sound types attributed to fish were recorded at depth (Bolgan et al., 2020; Wall et al., 2013, 2017).…”

“…Therefore, a fundamental requirement for a successful PAM of deep‐sea fish is a type of deployment which minimizes self‐noise (Rountree et al., 2020; Rountree & Juanes, 2010; Wall et al., 2014). This is the case of static acoustic monitoring (SAM; Bolgan et al., 2020; Carriço et al., 2019; Carriço et al, in press; Cato, 1978; McCauley & Cato, 2016; Wall et al., 2013) and of gliders (Bolgan et al., 2020; Wall et al., 2013, 2017). SAM is static and silent devices (i.e., hydrophone arrays deployed on the sea bottom) already used to record deep‐sea fish sounds, for example in the Bahamas (Mann & Jarvis, 2004), in the West Florida Shelf (USA; Wall et al., 2013), in the Perth canyon (AUS) (McCauley & Cato, 2016) and in Azores seamounts (Carriço et al., 2019; Carriço et al, in press).…”

“…In particular, the combination of hydrophone‐integrated gliders (mobile acoustic monitoring, MAM) with static acoustic monitoring (SAM), joined with advanced signal processing tools, could provide a holistic understanding of the biology of deep‐sea fish species and of ecosystem dynamics over large spatial and temporal scales. SAM can provide long‐term acoustic data which inform on diel and seasonal patterns of activity (Carriço et al, in press), while MAM can inform on large‐scale, stratigraphic distribution of vocal populations (Bolgan et al., 2020). The use of video cameras with integrated sound recorders is required to identify fish species, to link acoustic diversity to specific diversity, to assess the commercial interest of the identified species and to estimate their relative abundance (Mouy, Rountree, Juanes, & Dosso, 2018).…”

“…A small number of passive acoustic studies have monitored fish vocal activities in the deep sea (Bolgan et al., 2020; Carriço, Silva, Menezes, Fonseca, & Amorim, 2019; Carriço et al, in press; Cato, 1978; Kelly, Kewley, & Burgess, 1985; Mann & Jarvis, 2004; McCauley & Cato, 2016; Rountree et al., 2012; Wall, Simard, Lembke, & Mann, 2013; Wall et al., 2014; Wall et al., 2017; see Table 1). These pioneering studies provide valuable lessons for maximizing further attempts.…”