First observations of anthropogenic underwater noise in a large multi-use lake

Over the last fifty years, anthropogenic noise has increased dramatically in aquatic environments and is now recognised as a chronic form of pollution in coastal waters. However, this form of pollution has been largely neglected in inland water bodies. To date, very few studies have investigated the noise spectra in freshwater environments and at present no legislation exists to protect freshwater organisms from anthropogenic noise. The present study represents the first assessment of anthropogenic noise pollution in a large multi-use lake by characterising noise levels of the main ferry landings of the lake of Windermere, UK using Passive Acoustic Monitoring (PAM). During November 2014, acoustic samples (10 min long) were collected from such areas using a calibrated omni-directional hydrophone and their spectral content was analysed in 1/3 octave bands (dB re 1 µPa). Results indicate that the current noise levels in Windermere warrant further investigation as a potential threat to the fish community which occurs in this already delicate and pressured habitat. Based on results obtained, it is recommended that further studies focus on a wider geographical and temporal range in order to start to fill the knowledge and legislative gaps regarding anthropogenic noise monitoring in fresh waters

Use of passive acoustic monitoring to fill knowledge gaps of fish global conservation status

peer reviewed1. Knowledge of the ecology, spatial distribution and conservation status of fish populations is achieved by fishery-dependent techniques, and by more recently developed non-invasive fishery-independent techniques. Passive acoustic monitoring (PAM) is a fishery-independent method that provides remote sensing of soniferous species, populations, communities and ecosystems by recording soundscapes and their components. 2. A case study is presented to demonstrate how PAM can contribute to a dynamic understanding of fish distribution, ecological preferences and conservation status. This case study refers to the cusk-eel Ophidion rochei (Ophidiiformes), a nocturnal, behaviourally cryptic, soniferous fish species, described as uncommon and rare in the scientific literature, and listed as Data Deficient in the IUCN Red List. 3. A systematized literature review was carried out using Ophidion+rochei as the search term, and by grouping records into two main categories: (i) traditional techniques (including all fishery-dependent techniques and underwater visual census); and (ii) PAM. 4. This review highlights how PAM has provided new sightings of O. rochei at a rate three times higher than all other monitoring techniques combined. In contrast with the knowledge achieved to date by fishery-dependent techniques, the reported acoustic mass phenomena indicate that this species can be very abundant. Ophidion rochei was found to inhabit a wide range of depths and ecosystems, at least throughout the Mediterranean basin. 5. This paper supports the urgency and the importance of relying on the integration of different fishery-independent techniques for multidisciplinary monitoring, in line with the Goal 14 requirements of the UN Decade of Ocean Science for Sustainable Development

An investigation of inland water soundscapes: which sonic sources influence acoustic levels?

Acoustic recordings were carried out in two different glacial lakes (i.e. Lough Na Fooey, Ireland and Windermere, U.K) using different Passive Acoustic Monitoring approaches. At Lough Na Fooey, a vessel-based survey over pre-established sampling stations covering the entire lake surface (together with a bottom survey) was carried out, while a moored sampling was carried out around the clock at selected sites in the shallow, gravel littoral shores of Windermere. Lough Na Fooey soundscape lacked both the biophony and anthrophony component. Night-time recordings from Windermere were characterized by biophony sources, such as invertebrate (family Corixidae) and fish air passage sounds. Day-time acoustic recordings from Windermere were characterized by consistent boat traffic noise. Classification models were used to investigate which sonic sources contributed to the detected noise levels. The results indicate anthropogenic noise as an important factor ruling freshwater soundscapes. Based on the results obtained, it is recommended that further studies focus on a wider geographical and temporal range in order to start filling the knowledge and legislative gaps regarding anthropogenic noise monitoring in inland waters

An acoustic Odyssey: Characterisation of the vocal fish community inhabiting Neptune seagrass meadows across the Mediterranean Sea.

Passive acoustic monitoring (PAM) uses hydrophones to record all components of underwater soundscapes, including fish calls. Several studies have used PAM to investigate different aspects of vocal fish species, such as presence, distribution, relative abundance, diel, lunar and seasonal cycle of activity as well as for delimitating spawning areas and for studying wild fish spawning behaviour. A recent study conducted in Mediterranean rocky reefs has proved that the analysis of vocal fish communities provides high discrimination potential of species assemblages. Aside from this study, most investigations to date have considered fish species in isolation, and there is a general paucity of data addressing acoustic communication of fishes living in natural communities. We present a preliminary characterisation of vocal fish communities over a geographical and environmental gradient in Mediterranean Posidonia oceanica meadows and adjacent areas. We compared abundance and diversity of fish sounds recorded during the peak of fish vocal season in Posidonia oceanica meadows (-20 m) along a longitudinal axis (Mallorca, Corsica and Crete). These results are discussed in a framework that highlights the investment of different vocal fish species in partitioning their active acoustic space (in terms of both frequency and time) over small- and large-scale gradients. Our study supports the potential of PAM to provide high resolution information on fish population dynamics

Vocal repertoire and consistency of call features in the meagre Argyrosomous regius (Asso, 1801)

Passive Acoustic Monitoring (PAM) is a non-intrusive and cost-effective method capable of providing high-resolution, long-term information on the status and health of vocal populations and communities. To successfully monitor the same species over wide geographical and temporal scales, it is necessary to characterise the range of sound variability, as well as the consistency of sound features between populations. The meagre (Argyrosomus regius, Asso 1801) is an interesting case study because recent investigations suggest a wider vocal repertoire than previously described. In this study, meagre vocalizations were recorded and analysed from a variety of settings, ranging from rearing facilities to wild populations to provide a comprehensive characterisation of its vocal repertoire, while investigating the consistency of spawning sound features between populations. All sounds presented a similar acoustic structure in their basic unit (i.e. the pulse), while an important variability was found in the number of pulses; the meagre can emit sounds made of one single pulse or many pulses (up to more than 100). High level of overlap in the Principal Component Analysis made difficult to differentiate sound type clusters. Despite this, two sound types were identifiable: knocks (sounds from 1 to 3 pulses) and long grunts (sounds with more than 29 pulses). Discriminant Analysis carried out on PCA residuals showed that knock had the highest proportion of correct placement (92% of the observations correctly placed) followed by long grunts (80%). All other previously described sound types (intermediate grunt, short grunt and disturbance sounds) could not be separated and presented low levels of correct placement, suggesting that care should be taken when defining these as independent sound types. Finally, acoustic features consistency was found in meagre grunts emitted by different populations during spawning nights; statistical differences could be explained by recording settings and fish conditions. The results of this study provide important information for fostering PAM programs of wild meagre populations, while contributing to the discussion around the definition of fish sound types in vocal fish communities. Studies of this kind, which evaluate both variability and consistency of sound features, are of fundamental importance for maximising PAM efforts in the wild, at both the specific and the community level.info:eu-repo/semantics/publishedVersio

Fish biophony in a Mediterranean submarine canyon: a preliminary investigation using Static Acoustic Monitoring and gliders

Submarine canyons are key structures for ecosystem functioning in the Mediterranean Sea. This study was conducted in the canyon of Calvi (North-West Corsica, France) by using a combination of Static Acoustic Monitoring (SAM) and hydrophone integrated gliders (Seaexplorer, Alseamar). During summer 2016 and 2017, three SAM campaigns (-125 m to -150 m, 3 kilometers from coastline) and one gliders mission (-900 m to -60 m, 6 kilometers to 3 kilometers from coastline) were here conducted. A total of 194 hours of recordings were analysed for fish sound diversity (i.e. number of sound types) and for fish sound abundance (number of sounds per sound type and per unit of time). Biological sounds were detected in 37% of the recorded audio files. Besides for the presence of marine mammals clicks and whistles, at least 9 sound types (for a total of more than 8.000 sounds) with characteristics similar to those emitted by known vocal fish species were characterised; for one of these, emitter identity could be inferred at the genus level (Ophidion sp.). Furthermore, an increase in Sea Ambient Noise between 10 and 15 dB re 1 µPa was observed during daytime hours due to boat traffic. The vastness of the deep-sea and, in particular, the heterogeneity of submarine canyons, their high biodiversity and level of fauna specificity, together with the very localized character of observations carried out to date fully justify the use of an holistic monitoring approach such as PAM, especially when a combination of methods is used (e.g. SAM and gliders). Our study demonstrate that PAM can provide novel information about the ecoacoustics and the distribution of vocal fish species in these pivotal Mediterranean environments and can assess the contribution of anthropogenic sound and their adverse effects (such as masking) on fishes

Acoustic complexity of vocal fish communities: A field and controlled validation

The Acoustic Complexity Index (ACI) is increasingly applied to the study of biodiversity in aquatic habitats. However, it remains unknown which types of acoustic information are highlighted by this index in underwater environments. This study explored the robustness of the ACI to fine variations in fish sound abundance (i.e. number of sounds) and sound diversity (i.e. number of sound types) in field recordings and controlled experiments. The ACI was found to be sensitive to variations in both sound abundance and sound diversity, making it difficult to discern between these variables. Furthermore, the ACI was strongly dependent on the settings used for its calculation (i.e. frequency and temporal resolution of the ACI algorithm, amplitude filter). Care should thus be taken when comparing ACI absolute values between studies, or between sites with site-specific characteristics (e.g. species diversity, fish vocal community composition). As the use of ecoacoustic indices presents a promising tool for the monitoring of vulnerable environments, methodological validations like those presented in this paper are of paramount importance in understanding which biologically important information can be gathered by applying acoustic indices to Passive Acoustic Monitoring data.info:eu-repo/semantics/publishedVersio

Detection of invasive fish species with passive acoustics: Discriminating between native and non-indigenous sciaenids

Invasive alien species have been rising exponentially in the last decades impacting biodiversity and ecosystem functioning. The soniferous weakfish, Cynoscion regalis, is a recent invasive sciaenid species in the Iberian Peninsula and was first reported in the Tagus estuary in 2015. There is concern about its possible impacts on native species, namely the confamiliar meagre, Argyrosomus regius, as there is overlap in their feeding regime, habitat use, and breeding behaviour. Here, we characterised the sciaenid-like sounds recently recorded in the Tagus estuary and showed that they are made by weakfish as they have similar numbers of pulses and pulse periods to the sounds made by captive breeding weakfish. We further demonstrate that breeding grunts from weakfish and the native sciaenid, recorded either in captivity or Tagus estuary, differ markedly in sound duration, number of pulses and pulse period in the two species, but overlap in their spectral features. Importantly, these differences are easily detected through visual and aural inspections of the recordings, making acoustic recognition easy even for the non-trained person. We propose that passive acoustic monitoring can be a cost-effective tool for in situ mapping of weakfish outside its natural distribution and an invaluable tool for early detection and to monitor its expansion.Fundação para a Ciência e Tecnologia - FCTinfo:eu-repo/semantics/publishedVersio

Sound production in freshwater habitats of New England: widespread occurrence of air movements sounds

We conducted a roving survey of five major river systems and adjacent, creek, lake, and pond habitats located within the northeastern United States. Fish sounds were recorded in 49% of 175 locations. Air movement sounds, including fast repetitive tick (FRT), occurred at 41% of the locations. Sluggish creeks had the highest occurrence of fish sounds (71%). Although highly variable, creeks and brooks had the lowest noise levels and rivers the highest. Fish sounds were more frequent in low noise habitats than high noise habitats, but the effect of masking on detection is not clear. Within main-stem river habitats, fish sound diversity tended to increase along a gradient from high elevation to the sea. Follow-up studies validated air movement sounds produced by alewife, white sucker, and brook, brown and rainbow trout through direct observation or in observations where only single species were present. Sounds produced by all five species are of the “air movement” type which is poorly understood but occurs widely in freshwater habitats. Although air movement sounds are likely incidental to physiological processes, they appear to be uniquely identifiable to species and, hence, hold promise for passive acoustic studies of freshwater soundscapes and fish behavior

The unexploited potential of listening to deep-sea fish

Covering more than 65% of the Earth surface, the deep sea (200–11,000 m depth) is the largest biotope on Earth, yet it remains largely unexplored. The biology of its communities is still poorly understood, and many species are still to be discovered. Despite this, deep-sea fish are already threatened by our exploitation and their conservation is hampered by a severe scarcity of data. Studies focusing on fish acoustic communication are receiving growing attention in coastal areas as they provide useful information to different fields, ranging from behaviour, ecology, wild population monitoring, biodiversity assessment, fisheries and aquaculture management. Modern non-invasive techniques such as passive acoustic monitoring (PAM) can provide high-resolution, long-term and large spatial scale information on populations and ecosystem dynamics in otherwise not accessible environments. Although acoustic communication of deep-sea fish is still poorly documented, many deep-sea species are likely to emit sounds as they possess the required anatomical structures. Here we suggest that monitoring deep-sea fish vocal communication might help to better understand their diversity, ecology and dynamics. Emerging technologies based on PAM have the potential to provide a holistic view of the importance of acoustic communication for deep-sea fish and, ultimately, to inform us about essential aspects for their management and protection