Actively soniferous tropical reef fishes are diverse, vulnerable, and valuable

Active (i.e., intentional) fish sound production provides informative cues for numerous ecological functions, including larval recruitment or reproduction, and can facilitate monitoring and restoration. It is therefore important to have a holistic picture of actively soniferous tropical reef fish diversity, particularly in the face of growing threats such as noise pollution and habitat degradation. This study integrates fish biodiversity and sonifery datasets to assess the prevalence and ecological characteristics of actively soniferous tropical reef fishes. There are 258 known sound-producing species, which span 46 families, encompass a variety of life-history (e.g., lifespan) and distribution (e.g., depth) attributes, and include many vulnerable and commercially valuable species. Furthermore, up to 75% of tropical reef fish species are considered likely to produce active sounds. This synthesis should encourage a greater appreciation for active fish sound production in tropical reef environments and advance efforts to incorporate soundscape ecology into management and restoration strategies.

Listening to animal behavior to understand changing ecosystems

Interpreting sound gives powerful insight into the health of ecosystems. Beyond detecting the presence of wildlife, bioacoustic signals can reveal their behavior. However, behavioral bioacoustic information is underused because identifying the function and context of animals' sounds remains challenging. A growing acoustic toolbox is allowing researchers to begin decoding bioacoustic signals by linking individual and population-level sensing. Yet, studies integrating acoustic tools for behavioral insight across levels of biological organization remain scarce. We aim to catalyze the emerging field of behavioral bioacoustics by synthesizing recent successes and rising analytical, logistical, and ethical challenges. Because behavior typically represents animals' first response to environmental change, we posit that behavioral bioacoustics will provide theoretical and applied insights into animals' adaptations to global change.

Acoustic fish community in the Madeira Archipelago (North Atlantic Ocean): Characterization of sound diversity and daily patterns

Marine ecosystems are increasingly subjected to anthropogenic pressures, which demands urgent monitoring plans. Understanding soundscapes can offer unique insights into the ocean status providing important information and revealing different sounds and their sources. Fishes can be prominent soundscape contributors, making passive acoustic monitoring (PAM) a potential tool to detect the presence of vocal fish species and to monitor changes in biodiversity. The major goal of this research was to provide a first reference of the marine soundscapes of the Madeira Archipelago focusing on fish sounds, as a basis for a long-term PAM program. Based on the literature, 102 potentially vocal and 35 vocal fish species were identified. Additionally 43 putative fish sound types were detected in audio recordings from two marine protected areas (MPAs) in the Archipelago: the Garajau MPA and the Desertas MPA. The Garajau MPA exhibited higher fish vocal activity, a greater variety of putative fish sound types and higher fish sound diversity. Lower abundance of sounds was found at night at both MPAs. Acoustic activity revealed a clear distinction between diurnal and nocturnal fish groups and demonstrated daily patterns of fish sound activity, suggesting temporal and spectral partitioning of the acoustic space. Pomacentridae species were proposed as candidates for some of the dominant sound types detected during the day, while scorpionfishes (Scorpaena spp.) were proposed as sources for some of the dominant nocturnal fish sounds. This study provides an important baseline about this community acoustic behaviour and is a valuable steppingstone for future non-invasive and cost-effective monitoring programs in Madeira.

The potential of acoustic monitoring of aquatic insects for freshwater assessment

Aquatic insects are a major indicator used to assess ecological condition in freshwater environments. However, current methods to collect and identify aquatic insects require advanced taxonomic expertise and rely on invasive techniques that lack spatio-temporal replication. Passive acoustic monitoring (PAM) is emerging as a non-invasive complementary sampling method allowing broad spatio-temporal and taxonomic coverage. The application of PAM in freshwater ecosystems has already proved useful, revealing unexpected acoustic diversity produced by fishes, amphibians, submerged aquatic plants, and aquatic insects. However, the identity of species producing sounds remains largely unknown. Among them, aquatic insects appear to be the major contributor to freshwater soundscapes. Here, we estimate the potential number of soniferous aquatic insects worldwide using data from the Global Biodiversity Information Facility. We found that four aquatic insect orders produce sounds totalling over 7000 species. This number is probably underestimated owing to poor knowledge of aquatic insects bioacoustics. We then assess the value of sound producing aquatic insects to evaluate ecological condition and find that they might be useful despite having similar responses in pristine and degraded environments in some cases. Both expert and automated identifications will be necessary to build international reference libraries and to conduct acoustic bioassessment in freshwaters. This article is part of the theme issue 'Towards a toolkit for global insect biodiversity monitoring'.

Global inventory of species categorized by known underwater sonifery

A working group from the Global Library of Underwater Biological Sounds effort collaborated with the World Register of Marine Species (WoRMS) to create an inventory of species confirmed or expected to produce sound underwater. We used several existing inventories and additional literature searches to compile a dataset categorizing scientific knowledge of sonifery for 33,462 species and subspecies across marine mammals, other tetrapods, fishes, and invertebrates. We found 729 species documented as producing active and/or passive sounds under natural conditions, with another 21,911 species deemed likely to produce sounds based on evaluated taxonomic relationships. The dataset is available on both figshare and WoRMS where it can be regularly updated as new information becomes available. The data can also be integrated with other databases (e.g., SeaLifeBase, Global Biodiversity Information Facility) to advance future research on the distribution, evolution, ecology, management, and conservation of underwater soniferous species worldwide.

The role of acoustic signals in fish reproductiona)

This paper outlines my research path over three decades while providing a review on the role of fish sounds in mate choice and reproduction. It also intends to provide advice to young scientists and point toward future avenues in this field of research. An overview of studies on different fish model species shows that male mating acoustic signals can inform females and male competitors about their size (dominant frequency, amplitude, and sound pulse rate modulation), body condition (calling activity and sound pulse rate), and readiness to mate (calling rate, number of pulses in a sound). At least in species with parental care, such as toadfishes, gobies, and pomacentrids, calling activity seems to be the main driver of reproductive success. Playback experiments ran on a restricted number of species consistently revealed that females prefer vocal to silent males and select for higher calling rates. This personal synthesis concludes with the suggestion to increase knowledge on fish mating signals, especially considering the emerging use of fish sounds to monitor aquatic environments due to increasing threats, like noise pollution.

Habitat type drives the spatial distribution of Australian fish chorus diversitya)

Fish vocalize in association with life functions with many species calling en masse to produce choruses. Monitoring the distribution and behavior of fish choruses provides high-resolution data on fish distribution, habitat use, spawning behavior, and in some circumstances, local abundance. The purpose of this study was to use long-term passive acoustic recordings to obtain a greater understanding of the patterns and drivers of Australian fish chorus diversity at a national scale. This study detected 133 fish choruses from year-long recordings taken at 29 Australian locations with the highest fish chorus diversity identified at a site in the country's northern, tropical waters. A linear model fitted with a generalized least squares regression identified geomorphic feature type, benthic substrate type, and northness (of slope) as explanatory variables of fish chorus diversity. Geomorphic feature type was identified as the significant driver of fish chorus diversity. These results align with broad-scale patterns reported previously in fish biodiversity, fish assemblages, and fish acoustic diversity. This study has highlighted that passive acoustic monitoring of fish chorus diversity has the potential to be used as an indicator of fish biodiversity and to highlight habitats of ecological importance.

Tank acoustics substantially distort broadband sounds produced by marine crustaceans

Marine crustaceans produce broadband sounds that have been mostly characterized in tanks. While tank physical impacts on such signals are documented in the acoustic community, they are overlooked in the bioacoustic literature with limited empirical comparisons. Here, we compared broadband sounds produced at 1 m from spiny lobsters (Panulirus argus) in both tank and in situ conditions. We found significant differences in all sound features (temporal, power, and spectral) between tank and in situ recordings, highlighting that broadband sounds, such as those produced by marine crustaceans, cannot be accurately characterized in tanks. We then explained the three main physical impacts that distort broadband sounds in tanks, respectively known as resonant frequencies, sound reverberation, and low frequency attenuation. Tank resonant frequencies strongly distort the spectral shape of broadband sounds. In the high frequency band (above the tank minimum resonant frequency), reverberation increases sound duration. In the low frequency band (below the tank minimum resonant frequency), low frequencies are highly attenuated due to their longer wavelength compared to the tank size and tank wall boundary conditions (zero pressure) that prevent them from being accurately measured. Taken together, these results highlight the importance of understanding tank physical impacts when characterizing broadband crustacean sounds.

Discovering marine biodiversity in the 21st century

We review the current knowledge of the biodiversity of the ocean as well as the levels of decline and threat for species and habitats. The lack of understanding of the distribution of life in the ocean is identified as a significant barrier to restoring its biodiversity and health. We explore why the science of taxonomy has failed to deliver knowledge of what species are present in the ocean, how they are distributed and how they are responding to global and regional to local anthropogenic pressures. This failure prevents nations from meeting their international commitments to conserve marine biodiversity with the results that investment in taxonomy has declined in many countries. We explore a range of new technologies and approaches for discovery of marine species and their detection and monitoring. These include: imaging methods, molecular approaches, active and passive acoustics, the use of interconnected databases and citizen science. Whilst no one method is suitable for discovering or detecting all groups of organisms many are complementary and have been combined to give a more complete picture of biodiversity in marine ecosystems. We conclude that integrated approaches represent the best way forwards for accelerating species discovery, description and biodiversity assessment. Examples of integrated taxonomic approaches are identified from terrestrial ecosystems. Such integrated taxonomic approaches require the adoption of cybertaxonomy approaches and will be boosted by new autonomous sampling platforms and development of machine-speed exchange of digital information between databases.

Soundscapes as heard by invertebrates and fishes: Particle motion measurements on coral reefs

Coral reef soundscapes are increasingly studied for their ecological uses by invertebrates and fishes, for monitoring habitat quality, and to investigate effects of anthropogenic noise pollution. Few examinations of aquatic soundscapes have reported particle motion levels and variability, despite their relevance to invertebrates and fishes. In this study, ambient particle acceleration was quantified from orthogonal hydrophone arrays over several months at four coral reef sites, which varied in benthic habitat and fish communities. Time-averaged particle acceleration magnitudes were similar across axes, within 3 dB. Temporal trends of particle acceleration corresponded with those of sound pressure, and the strength of diel trends in both metrics significantly correlated with percent coral cover. Higher magnitude particle accelerations diverged further from pressure values, potentially representing sounds recorded in the near field. Particle acceleration levels were also reported for boat and example fish sounds. Comparisons with particle acceleration derived audiograms suggest the greatest capacity of invertebrates and fishes to detect soundscape components below 100 Hz, and poorer detectability of soundscapes by invertebrates compared to fishes. Based on these results, research foci are discussed for which reporting of particle motion is essential, versus those for which sound pressure may suffice.

Toward understanding the communication in sperm whales

Machine learning has been advancing dramatically over the past decade. Most strides are human-based applications due to the availability of large-scale datasets; however, opportunities are ripe to apply this technology to more deeply understand non-human communication. We detail a scientific roadmap for advancing the understanding of communication of whales that can be built further upon as a template to decipher other forms of animal and non-human communication. Sperm whales, with their highly developed neuroanatomical features, cognitive abilities, social structures, and discrete click-based encoding make for an excellent model for advanced tools that can be applied to other animals in the future. We outline the key elements required for the collection and processing of massive datasets, detecting basic communication units and language-like higher-level structures, and validating models through interactive playback experiments. The technological capabilities developed by such an undertaking hold potential for cross-applications in broader communities investigating non-human communication and behavioral research.

Combining Passive Acoustics and Environmental Data for Scaling Up Ecosystem Monitoring: A Test on Coral Reef Fishes

Ecological surveys of coral reefs mostly rely on visual data collected by human observers. Although new monitoring tools are emerging, their specific advantages should be identified to optimise their simultaneous use. Based on the goodness-of-fit of linear models, we compared the potential of passive acoustics and environmental data for predicting the structure of coral reef fish assemblages in different environmental and biogeographic settings. Both data types complemented each other. Globally, the acoustic data showed relatively low added value in predicting fish assemblage structures. The predictions were best for the distribution of fish abundance among functional entities (i.e., proxies for fish functional groups, grouping species that share similar eco-morphological traits), for the simplest functional entities (i.e., combining two eco-morphological traits), and when considering diet and the level in the water column of the species. Our study demonstrates that Passive Acoustic Monitoring (PAM) improves fish assemblage assessment when used in tandem with environmental data compared to using environmental data alone. Such combinations can help with responding to the current conservation challenge by improving our surveying capacities at increased spatial and temporal scales, facilitating the identification and monitoring of priority management areas.

ecoSound-web: an open-source, online platform for ecoacoustics

Passive acoustic monitoring of soundscapes and biodiversity produces vast amounts of audio recordings, but the management and analyses of these raw data present technical challenges. A multitude of software solutions exist, but none can fulfil all purposes required for the management, processing, navigation, analysis, and dissemination of acoustic data. The field of ecoacoustics needs a software tool that is free, evolving, and accessible. We take a step in that direction and present ecoSound-web: an open-source, online platform for ecoacoustics designed and built by ecologists and software engineers. ecoSound-web can be used for storing, organising, and sharing soundscape projects, manually creating and peer-reviewing annotations of soniferous animals and phonies, analysing audio in time and frequency, computing alpha acoustic indices, and providing reference sound libraries for different taxa. We present ecoSound-web's features, structure, and compare it with similar software. We describe its operation mode and the workflow for typical use cases such as the sampling of bird and bat communities, the use of a primate call library, and the analysis of phonies and acoustic indices. ecoSound-web is available from: https://github.com/ecomontec/ecoSound-web.

ecoSound-web: an open-source, online platform for ecoacoustics

Passive acoustic monitoring of soundscapes and biodiversity produces vast amounts of audio recordings, but the management and analyses of these raw data present technical challenges. A multitude of software solutions exist, but none can fulfil all purposes required for the management, processing, navigation, and analysis of acoustic data. The field of ecoacoustics needs a software tool that is free, evolving, and accessible. We take a step in that direction and present ecoSound-web: an open-source, online platform for ecoacoustics designed and built by ecologists and software engineers. ecoSound-web can be used for storing, re-sampling, organising, analysing, and sharing soundscape recording or metadata projects. Specifically, it allows manual annotation of soniferous animals and soundscape components, automatic annotation with deep-learning models for all birds and for UK bat species, peer-reviewing annotations, analysing audio in time and frequency dimensions, computing alpha acoustic indices, and providing reference sound libraries for different taxa. We present ecoSound-web's structure and features, and describe its operation for typical use cases such as sampling bird and bat communities, using a primate call library, and the analysis of soundscape components and acoustic indices. ecoSound-web is available from: https://github.com/ecomontec/ecoSound-web.