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.

Monitoring the biodiversity of key habitats and understanding the drivers across spatial scales is essential for preserving ecosystem functions and associated services. Coralligenous reefs are threatened marine biodiversity hotspots that are challenging to monitor. As fish sounds reflect biodiversity in other habitats, we unveiled the biogeography of coralligenous reef sounds across the north-western Mediterranean using data from 27 sites covering 2000 km and 3 regions over a 3-year period. We assessed how acoustic biodiversity is related to habitat parameters and environmental status. We identified 28 putative fish sound types, which is up to four times as many as recorded in other Mediterranean habitats. 40% of these sounds are not found in other coastal habitats, thus strongly related to coralligenous reefs. Acoustic diversity differed between geographical regions. Ubiquitous sound types were identified, including sounds from top-predator species and others that were more specifically related to the presence of ecosystem engineers (red coral, gorgonians), which are key players in maintaining habitat function. The main determinants of acoustic community composition were depth and percentage coverage of coralligenous outcrops, suggesting that fish-related acoustic communities exhibit bathymetric stratification and are related to benthic reef assemblages. Multivariate analysis also revealed that acoustic communities can reflect different environmental states. This study presents the first large-scale map of acoustic fish biodiversity providing insights into the ichthyofauna that is otherwise difficult to assess because of reduced diving times. It also highlights the potential of passive acoustics in providing new aspects of the correlates of biogeographical patterns of this emblematic habitat relevant for monitoring and conservation.

Marine communities face anthropogenic pressures that degrade ecosystems. Because underwater soundscapes carry information about habitat quality, we explored whether destructive impacts of fishing could be evaluated via the soundscape. Maerl beds are recognized as biodiversity hotspots and they experience major worldwide degradation owing to fishing. We collected field acoustic recordings in maerl beds exposed to different fishing practices. We found that unfished maerl beds were threefold louder and exhibited sound frequencies more diversified than those recorded in fished maerl beds. Analyses of associated fauna samples indicated that snapping shrimps provided a major contribution to the maerl bed soundscape. Moreover, sea urchins and squat lobsters most likely contributed to differences between the soundscapes of unfished and fished maerl beds. Our results supported the idea that the soundscape can provide valuable information on maerl bed ecosystem health related to fishing activity.

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The ability of different marine species to use acoustic cues to locate reefs is known, but the maximal propagation distance of coral reef sounds is still unknown. Using drifting antennas (made of a floater and an autonomous recorder connected to a hydrophone), six transects were realized from the reef crest up to 10 km in the open ocean on Moorea island (French Polynesia). Benthic invertebrates were the major contributors to the ambient noise, producing acoustic mass phenomena (3.5–5.5 kHz) that could propagate at more than 90 km under flat/calm sea conditions and more than 50 km with an average wind regime of 6 knots. However, fish choruses, with frequencies mainly between 200 and 500 Hz would not propagate at distances greater than 2 km. These distances decreased with increasing wind or ship traffic. Using audiograms of different taxa, we estimated that fish post-larvae and invertebrates likely hear the reef at distances up to 0.5 km and some cetaceans would be able to detect reefs up to more than 17 km. These results are an empirically based validation from an example reef and are essential to understanding the effect of soundscape degradation on different zoological groups.

20Conservation of exploited fish populations is a priority for environmental managers. Spatio-21 temporal knowledge on reproductive sites is mandatory for species and habitat conservation but 22 is often difficult to assess, particularly over vast geographic areas. Regular and long-term 23 standardized surveys are necessary to identify reproductive sites, assess population trends and 24 their distribution. Here we emphasize the utility of Passive Acoustic Monitoring (PAM) for the 25 survey and management of a depleted vulnerable Mediterranean fish species, the brown meagre, 26 Sciaena umbra. Acoustic surveys of reproductive calls were conducted combining 1) spatial 27 data from standardized surveys within three MPAs and from 49 unprotected sites throughout 28 the Northwestern Mediterranean basin, as well as 2) temporal data from a two-year-long survey 29 at a presumed spawning location. The MPA surveys, which rapidly scanned ~30-50 km of the 30 rocky coastlines per MPA, unveiled maps of distribution and reproductive activity of the brown 31 meagre, including potential spawning sites. They were also effective in emphasizing effects 32 linked to management actions: Full-protection zones had a higher number of vocalizations (70% 33 of the listening sites) compared to less protected zones (30% of the sites) or sites outside MPAs 34 (45% of the sites). This was also reflected in the number of singers that was generally low (< 3 35 individuals) in less protected zones and outside MPAs, implying lower fish densities. Highest 36 calling aggregations were observed in potential spawning areas that represented only 0.04% of 37 all listening sites, and were almost all in older, fully protected MPAs, which thus play a key 38 role for fish stock recovery. The two-year survey revealed a 5-month reproductive season (from 39 May to October) with a strong positive correlation between calling activity and temperature.40Overall this study confirms the role of PAM as an efficient, replicable and standardized non-41 invasive method for population management that can identify functional sites and key 42 protection zones, provide valuable information on reproduction, spatial and temporal 43 occurrence, but also on population trends and climate-driven changes. 44 3 45 46

No abstract

Coastal soundscapes are dominated by broadband transient sounds primarily emitted by benthic invertebrates. These sounds are characterized by a very large dynamic of amplitude. The loudest ones propagate further and interfere with the detectability of benthic sounds by invading other more distant habitats. Acoustic diversity assessment is therefore biased when applying acoustic indices related to the signal's power. Here, we propose new acoustic indices (IDSS: indices of the diversity of spectral shape) capable of extracting the diversity of the benthic invertebrate biophony (BIB) despite interference from loud and abundant sounds. A passive acoustic ecological survey was conducted in a shallow Mediterranean bay with a small-scale mosaic of biocenosis. The sound pressure level and spectrum of the BIB revealed that the rocky fringe had the most powerful biophony, propagating up to 3680 m, thus 'invading' other habitats. However, these power-based indices failed to depict BIB diversity. The IDSS allowed us to discriminate BIB diversity despite the interfering rocky fringe biophony, including low-power sounds not depicted by traditional power-based methods. Four main categories of benthic invertebrates sounds (BIS) spectra were found. Two categories (high-power, peak frequencies ~3 to 4 kHz) were mainly linked to the rocky fringe. Their contribution to the diversity (56%) decreased with increasing distance to the fringe, where low-power BIS (peak frequencies above 15 kHz) predominantly contributed to the BIB (42%) and may be specific to coralligenous reefs. The IDSS enables a better characterization and quantification of BIB diversity and soundscape structure with a fine spatial resolution (~200 m).