Fish Sounds Research Articles

Reliable characterization of sound features in fishes begins in open-water environmentsa).

Many fishes use sounds to communicate in a wide range of behavioral contexts. In monitoring studies, these sounds can be used to detect and identify species. However, being able to confidently link a sound to the correct emitting species requires precise acoustical characterization of the signals in controlled conditions. For practical reasons, this characterization is often performed in small sized aquaria, which, however, may cause sound distortion, and prevents an accurate description of sound characteristics that will ultimately impede sound-based species identification in open-water environments. This study compared the sounds features of five specimens of the silverspot squirrelfish Sargocentron caudimaculatum recorded at sea and in aquaria of different sizes and materials. Our results point out that it is preferable to record fish sounds in an open-water environment rather than in small aquaria because acoustical features are affected (sound duration and dominant frequency) when sounds are recorded in closed environments as a result of reverberation and resonance. If not possible, it is recommended that (1) sound recordings be made in plastic or plexiglass aquaria with respect to glass aquaria and (2) aquaria with the largest dimensions and volumes be chosen.

Identification of fish sounds in the wild using a set of portable audio‐video arrays

Abstract Associating fish sounds to specific species and behaviours is important for making passive acoustics a viable tool for monitoring fish. While recording fish sounds in tanks can sometimes be performed, many fish do not produce sounds in captivity. Consequently, there is a need to identify fish sounds in situ and characterise these sounds under a wide variety of behaviours and habitats. We designed three portable audio‐video platforms capable of identifying species‐specific fish sounds in the wild: a large array, a mini array and a mobile array. The large and mini arrays are static autonomous platforms than can be deployed on the seafloor and record audio and video for one to two weeks. They use multichannel acoustic recorders and low‐cost video cameras mounted on PVC frames. The mobile array also uses a multichannel acoustic recorder, but mounted on a remotely operated vehicle with built‐in video, which allows remote control and real‐time positioning in response to observed fish presence. For all arrays, fish sounds were localised in three dimensions and matched to the fish positions in the video data. We deployed these three platforms at four locations off British Columbia, Canada. The large array provided the best localisation accuracy and, with its larger footprint, was well suited to habitats with a flat seafloor. The mini and mobile arrays had lower localisation accuracy but were easier to deploy, and well suited to rough/uneven seafloors. Using these arrays, we identified, for the first time, sounds from quillback rockfish Sebastes maliger, copper rockfish Sebastes caurinus and lingcod Ophiodon elongatus. In addition to measuring temporal and spectral characteristics of sounds for each species, we estimated mean source levels for lingcod and quillback rockfish sounds (115.4 and 113.5 dB re 1 μPa, respectively) and maximum detection ranges at two sites (between 10.5 and 33 m). All proposed array designs successfully identified fish sounds in the wild and were adapted to various budget, logistical and habitat constraints. We include here building instructions and processing scripts to help users replicate this methodology, identify more fish sounds around the world and make passive acoustics a more viable way to monitor fish.

“To Be, or Not to Be”: Critical Assessment of the Use of α-Acoustic Diversity Indices to Evaluate the Richness and Abundance of Coastal Marine Fish Sounds

Passive acoustic monitoring can be used to assess the presence of vocal species. Automatic estimation of such information is critical for allowing diversity monitoring over long time spans. Among the existing tools, α-acoustic indices were originally designed to assess the richness/complexity of terrestrial soundscapes. However, their use in marine environments is impacted by fundamental differences between terrestrial and marine soundscapes. The aim of this study was to determine how they vary depending on the abundance and sound type richness of fish sounds. Fourteen indices used in terrestrial environments were tested. The indices were calculated for files from three sources: a controlled environment (playback of artificial tracks in a pool), in situ playbacks (playback of natural soundscapes), and a natural environment (only natural sounds). The controlled experiment showed that some indices were correlated with the sound abundance but not with the sound type richness, implying that they are not capable of distinguishing the different types of fish sounds. In the in situ playbacks, the indices were not able to capture differences, both in terms of the sound abundance and sound type diversity. In the natural environment, there was no correlation between most of the indices and the abundance of sounds. They were impacted by mass phenomena of biological sounds (e.g., the Pomacentridae sounds in shallow reefs) that cannot inform on fish acoustic diversity. Indices are appropriate when soundscapes are divided into bands. In contrast to terrestrial environments, frequency bands in coastal marine soundscapes do not provide ecologically relevant information on diversity. Overall, indices do not appear to be suitable for inferring marine fish sound diversity.

Fish sounds of photic and mesophotic coral reefs: variation with depth and type of island

Fish sounds of photic and mesophotic coral reefs: variation with depth and type of island

FishSounds Version 1.0: A website for the compilation of fish sound production information and recordings

Many fish species use active sound production for communication in numerous behaviors. Additionally, likely all fish can make passive or incidental sounds that may also serve some signal functions. Despite the ecological importance of fish sounds, their evident passive acoustic monitoring applications, and extensive endeavors to document soniferous fish diversity, the fields of bioacoustics and ichthyology have historically lacked an easily accessible, global inventory of known fish sound production. To alleviate this limitation, we developed http://FishSounds.net, a website that compiles and disseminates fish sound production information and recordings. FishSounds Version 1.0 launched in 2021, cataloging documented examinations for active and passive sound production for 1185 fish species from 837 references as well as 239 exemplary audio recordings. FishSounds allows users to search by taxa (e.g., family or common name), geographical distribution (e.g., region or water body), sound type, or reference. We have also made available the code used to create the website, so that it may be used in other data-sharing efforts—acoustic or otherwise. Subsequent versions of the website will update the data and improve the website functionality. FishSounds will advance research into fish behavior, passive acoustic monitoring, and human impacts on underwater soundscapes; serve as a resource for public outreach; and provide the foundation needed to investigate more of the 96% of fish species that lack published examinations of sound production. We further hope the FishSounds design, implementation, and engagement strategies will serve as a model for future data management and sharing efforts.

Diel, temporal, and spatial patterns of biotic soundscapes among Alabama artificial reefs in late spring and summer

Passive acoustic monitoring (PAM) in a variety of marine habitats has revealed distinct spatial and temporal variation of fish sounds that are predicted to vary in association with species composition and abundance, as well as diel and seasonal influences. Reefs in the Alabama Artificial Reef Zone (AARZ) in the northern Gulf of Mexico (nGOM) have an associated fish fauna composed of warm-temperate and tropical reef associated species. AARZ reefs are made of different structures (e.g. bridge rubble, concrete pyramids, etc.) and as a result, their fish species composition is predicted to vary. We used PAM to describe fish sounds on 18 shallow slope (20-33 m) AARZ reefs in 2017 and 2018. We detected calls from unknown sources, as well as sounds from leopard toadfishOpsanus pardus, cocoa damselfishStegastes variabilis, and cusk-eels (Ophidiidae). We developed semi-automated screening methods to detect specific sound types and described diel and spatial patterns. Sound detection rates varied widely among reefs, but not by reef type. Number of sound types increased with species richness, but detection rates of specific sounds differed on reefs with similar species composition. Our results indicate that many frequently occurring sounds may not be associated with visually conspicuous fishes. Further research is needed to determine source species and associated behavior for common sounds in these habitats. Soundscape variability among nGOM artificial reefs may be a consideration for management, as biological sound can provide an acoustic cue for reef location by some larval and adult fish species.

Hunting, Fighting, or Playing with Bubbles: Possible Usage and Acoustic Characteristics of Bubble Burst Sounds Produced by the Amazon River Dolphin (Inia geoffrensis)

Acoustic characteristics of bubble production by an odontocete were documented for the first time. Bubble sounds produced by the Amazon river dolphin (Inia geoffrensis) were recorded incidentally as part of a survey of fish sounds in the Pacaya–Samiria National Reserve of Peru on six dates between 4 and 24 July 2012. Dolphins were observed to periodically produce large clouds of bubbles underneath or near the survey boat (averaging 7/survey or 8/h) as it drifted through areas of actively foraging dolphins. The bubble production was classified as bubble bursts due to their similarity to bubble bursts produced by other cetaceans. Bubble burst sounds had a mean peak frequency of 402 Hz and duration of 8.9 s (n = 51). Bubble bursts were temporally clustered with an average interval of 169 s (0.1 to 1,187 s) between bursts. Bubble bursts were disproportionately more likely to be present when fish sounds were also present, but it is not known if the association was due to predation or other factors. A review of the literature finds similar bubble production has been reported in at least 14 other species of cetaceans (4 mysticetes and 10 odontocetes). Most are commonly associated with play, surprise, agonistic, and foraging behaviors. We discuss each of these possibilities and conclude that Amazon river dolphin bubble burst behavior is most likely related to foraging or aggressive behavior because the behavior occurred in feeding areas and appeared to be directed at the drifting boat. We further propose a novel hypothesis that the bubble bursts are a hunting strategy used to disperse prey associated with floating vegetation mats and other forms of drifting materials used by fishes for shelter. Future research is needed to better understand the behavior associated with bubble production by the Amazon river dolphin.

An investigation of bubble resonance and its implications for sound production by deep-water fishes.

Although the continental slope and abyss comprise the largest habitat on earth, the absence of documented fish sounds from deep waters is striking. Fishes with sexually dimorphic muscles attached to their swim bladders suggests that sounds are likely used in male courtship on the upper, mid and lower continental slope. To investigate the effects of environmental extremes on fish sound production, the acoustic behavior of a driven bubble is examined. This study is also relevant to target strength of sonar returns from fish and hearing in auditory specialist fishes. A bubble is a classic, if imperfect, model for swim bladder behavior since the swim-bladder wall is an anisotropic viscoelastic structure responsible for rapid damping. Acoustic properties of bubbles-including far-field resonant frequency, damping factor, and quality factor-are calculated in warm and cold surface conditions and in cold deep-water (depths 1000 m, 2000 m, and 3500 m) conditions using parameters for oxygen and nitrogen, the dominant gases in swim bladders. The far-field resonant frequency and damping factor of a bubble increase with depth, and the scattering cross-section and quality factor decrease with depth. These acoustic properties scale with undamped oscillation frequency of the bubble and do not vary significantly due to gas type or temperature. Bubbles in the deep-water environments are much less efficient radiators of sound than bubbles near the surface because the far-field radiated power for the same excitation decreases with depth. A bubble at depth 3500 m has a 25 dB loss in radiated sound power compared to the same-radius bubble at the surface. This reduction of radiation efficiency in deep water likely contributes to the absence of fish sound recordings in those environments.

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.

Comparison of three portable volumetric arrays to localize and identify fish sounds in the wild

We describe three portable volumetric audio/video arrays capable of identifying species-specific fish sounds in the wild. Each array can record fish sounds, acoustically localize the fish in three-dimensions (using linearized or fully non-linear inversion), and record video to identify the species and observe their behavior. The design of each array accommodates specific logistical and financial constraints, covering a range of nearshore habitats and applications. The first platform is composed of six hydrophones, an acoustic recorder, and two video cameras secured to a 2 × 2 × 3 m PVC frame. Hydrophone placement is defined using simulated annealing to maximize localization accuracy. The second platform uses a single video camera, four hydrophones, and an acoustic recorder on a one cubic meter PVC frame. It can be deployed on heterogeneous substrates but has lower localization capabilities. The third platform consists of four hydrophones connected to an acoustic recorder mounted on a tethered underwater drone with built-in video. It allows remote control and real-time positioning in response to observed fish presence but with reduced localization capabilities. The three platforms were deployed off British Columbia, Canada, and used to identify and characterize new sounds from quillback rockfish, copper rockfish, and lingcod.

Natural cues for invertebrate and fish hearing: Particle motion measurements on coral reefs

Coral reef soundscapes are increasingly studied for their ecological uses by invertebrates and fishes, their applications 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. We quantified ambient particle acceleration from orthogonal hydrophone arrays over several months at four coral reef sites in the U.S. Virgin Islands, which varied in benthic habitat and fish communities. Temporal trends of particle acceleration were similar to those of sound pressure, and the strength of diel trends in both metrics significantly correlated with percent coral cover. Low frequency (<100 Hz) and high magnitude empirical particle acceleration levels diverged from plane wave approximations. Particle acceleration levels were also determined for boat and example fish sounds. Comparisons with particle acceleration derived audiograms suggest greatest capacity of invertebrates and fishes to detect soundscape components below 100 Hz, and potentially poorer detectability of soundscape cues by some invertebrates compared to fishes. Based on our results, we discuss research questions in soundscape ecology for which reporting of particle motion is essential versus those for which sound pressure may suffice.

Fish acoustic community structure in Neptune seagrass meadows across the Mediterranean basin

Abstract Sound production represents an integral part of social communication in many teleost fish; however, few studies have investigated the structure, organization and variability of fish sounds at the community level. Fish acoustic community structure was recorded simultaneously in three sites located along the Mediterranean basin within the endemic habitat of Posidonia oceanica seagrass beds. Acoustic diversity and species‐specific sound features were expected to differ between locations. We predicted that, in communities characterized by higher acoustic richness, fish species would specialize in their use of acoustic resources (i.e. realized acoustic niche compression), while the overall allocation of resources within the community signal space would expand. The fish acoustic communities inhabiting Posidonia beds were characterized by the same main contributors (the /Kwa/, Ophidion rochei and Sciaena umbra sound types). However, their relative occurrence, abundances and use of acoustic resources were site‐specific. Acoustic diversity differed between geographic locations. The range of spectral and temporal resources exploited by the fish acoustic community was wider in sites where acoustic richness was at its highest score. Ophidion rochei was highly specialized in its use of temporal resources where acoustic richness was higher, whilst S. umbra appeared less efficient in specializing the use of spectral and temporal resources. By showing that the same species can exploit different acoustic resources between locations, this study supports the concept of Acoustic Niche plasticity (i.e. plasticity of acoustic resources allocation within a species). The results suggest that the degree of acoustic niche plasticity might be determined by the species‐specific degree of sound‐producing system plasticity. In turn, different degrees of acoustic niche plasticity might determine different species‐specific levels of acoustic adaptability to changing biotic or environmental conditions.

Marine soundscape and fish biophony of a Mediterranean marine protected area.

BackgroundMarine soundscape is the aggregation of sound sources known as geophony, biophony, and anthrophony. The soundscape analysis, in terms of collection and analysis of acoustic signals, has been proposed as a tool to evaluate the specific features of ecological assemblages and to estimate their acoustic variability over space and time. This study aimed to characterise the Capo Caccia-Isola Piana Marine Protected Area (Italy, Western Mediterranean Sea) soundscape over short temporal (few days) and spatial scales (few km) and to quantify the main anthropogenic and biological components, with a focus on fish biophonies.MethodsWithin the MPA, three sites were chosen each in a different protection zone (A for the integral protection, B as the partial protection, and C as the general protection). In each site, two underwater autonomous acoustic recorders were deployed in July 2020 at a depth of about 10 m on rocky bottoms. To characterise the contribution of both biophonies and anthrophonies, sea ambient noise (SAN) levels were measured as sound pressure level (SPL dB re: 1 μ Pa-rms) at eight 1/3 octave bands, centred from 125 Hz to 16 kHz, and biological and anthropogenic sounds were noted. Fish sounds were classified and counted following a catalogue of known fish sounds from the Mediterranean Sea based on the acoustic characteristic of sound types. A contemporary fish visual census had been carried out at the test sites.ResultsSPL were different by site, time (day vs. night), and hour. SPLs bands centred at 125, 250, and 500 Hz were significantly higher in the daytime, due to the high number of boats per minute whose noise dominated the soundscapes. The loudest man-made noise was found in the A zone, followed by the B and the C zone, confirming that MPA current regulations do not provide protection from acoustic pollution. The dominant biological components of the MPA soundscape were the impulsive sounds generated by some invertebrates, snapping shrimps and fish. The vast majority of fish sounds were recorded at the MPA site characterized by the highest sound richness, abundance, and Shannon-Wiener index, coherently with the results of a fish visual census. Moreover, the acoustic monitoring detected a sound associated with a cryptic species (Ophidion spp.) never reported in the study area before, further demonstrating the usefulness of passive acoustic monitoring as a complementary technique to species census. This study provides baseline data to detect future changes of the marine soundscapes and some suggestions to reduce the impact of noise on marine biodiversity.

A primer on rhythm quantification for fish sounds: aMediterranean case study.

We have used a lately established workflow to quantify rhythms of three fish sound types recorded in different areas of the Mediterranean Sea. So far, the temporal structure of fish sound sequences has only been described qualitatively. Here, we propose a standardized approach to quantify them, opening the path for assessment and comparison of an often underestimated but potentially critical aspect of fish sounds. Our approach is based on the analysis of inter-onset-intervals (IOIs), the intervals between the start of one sound element and the next. We calculate exact beats of a sequence using Fourier analysis and IOI analysis. Furthermore, we report on important parameters describing the variability in timing within a given sound sequence. Datasets were chosen to depict different possible rhythmic properties: Sciaena umbra sounds have a simple isochronous—metronome-like—rhythm. The /Kwa/ sound type emitted by Scorpaena spp. has a more complex rhythm, still presenting an underlying isochronous pattern. Calls of Ophidion rochei males present no rhythm, but a random temporal succession of sounds. This approach holds great potential for shedding light on important aspects of fish bioacoustics. Applications span from the characterization of specific behaviours to the potential discrimination of yet not distinguishable species.

Biogeography of acoustic biodiversity of NW Mediterranean coralligenous reefs

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.

Fish sounds and boat noise are prominent soundscape contributors in an urban European estuary

Passive acoustic monitoring is a valuable tool for non-intrusive monitoring of marine environments, also allowing the assessment of underwater noise that can negatively affect marine organisms. Here we provide for the first time, an assessment of noise levels and temporal soundscape patterns for a European estuary. We used several eco-acoustics methodologies to characterize the data collected over six weeks within May 2016 - July 2017 from Tagus estuary. Biophony was the major contributor dominated by fish vocalizations and the main driver for seasonal patterns. Maritime traffic was the major source of anthropogenic noise, with daily patterns monitored using 1584 Hz third-octave band level. This indicator avoided biophony and geophony, unlike other indicators proposed for the EU Marine Strategy Framework Directive. Furthermore, the frequency overlap between anthropophony and biophony demands precautionary actions and calls for further research. This study provides an assessment that will be useful for future monitoring and management strategies.

A Fish Chorus on the Margin of New Jersey Atlantic Continental Shelf

We report herein an underwater biological chorus coming from the margin of the New Jersey Atlantic continental shelf that we tentatively attribute to a species of fish. The chorus occurred every night for over a month during the Shallow Water 2006 experiment and covers the frequency band 150–4,800 Hz, with maximum intensity in the band from 1450 to 2,000 Hz. Remarkable intensity peaks occurred at 500, 725, 960, 1,215, 1,465, 1,700, and 1,920 Hz, rising to as much as 20 dB above the background noise without the chorus. The chorus begins at sunset and reaches its maximum intensity within an hour, following which it weakens slightly and then gradually climbs again to a peak before sunrise, at which point it quickly weakens and disappears. Its frequency-domain characteristics and the nocturnal timing are reminiscent of sound produced by underwater animals. The intensity of the chorus weakens along the across-shelf path going shoreward, which indicates that the chorus originates from the margin of the continental shelf rather than from the coastal zone, as is generally considered. The chorus contains a single type of acoustic signal that takes the form of double-pulse bursts that last about 8.7 ms, with each pulse containing several acoustic cycles. The time interval between successive bursts varies from 1.5 to 1.9 s. Signals containing a number of bursts vary in length from tens to hundreds of seconds. Although it is impossible to determine the fish species responsible for the chorus, its characteristics, including its low frequency and intensity, its single type of short-duration sound signal, and its multiple peaks in the frequency domain, are all consistent with the general characteristics of fish sounds.

Parrotfish soundscapes: implications for coral reef management

Parrotfishes are prominent members of the herbivore/detritivore feeding guild on coral reefs. Their feeding activity is important for the removal of algae and detritus, the clearing of new settlement sites for coral and other larvae, and the bioerosion and redistribution of sand across the reef. Estimates of parrotfish feeding activity are normally obtained by divers that may influence or overlook fish behaviors, and are of short duration, limited to shallow habitats, and have limited temporal resolution to associate feeding activity with ecological processes. Excavator and scraper parrotfishes have a robust beak-like jaw morphology that produces a unique sound as the teeth scrape the surface of hard coral rock. We tested the hypothesis that ambient parrotfish bite sounds can be used to estimate their temporal patterns of feeding and associations with environmental variates in the area of an acoustic recorder. Acoustic recorders were deployed on 2 Hawaiian reefs to collect ambient fish sounds for a period of 3 yr. Parrotfish bite sounds showed distinct and repetitive variations in daily, seasonal, and annual feeding patterns, and were statistically correlated with factors of day length and tide range. This study demonstrates the utility of using parrotfish bite sounds to estimate patterns of feeding at coral reef sites. We suggest that regular sampling by multiple acoustic monitors may be a cost-efficient and valuable tool for monitoring the health, degradation, and recovery of large coral reef areas.

The utility of different acoustic indicators to describe biological sounds of a coral reef soundscape

Monitoring coral reefs is vital to the conservation of these at-risk ecosystems. While most current monitoring methods are costly and time-intensive, passive acoustic monitoring (PAM) could provide a cost-effective, large scale reef monitoring tool. However, for PAM to be reliable, the results must be field tested to ensure that the acoustic methods used accurately represent the certain ecological components of the reef being studied. For example, recent acoustic studies have attempted to describe the diversity of coral reef fish using the Acoustic Complexity Index (ACI) but despite inconsistent results on coral reefs, ACI is still being applied to these ecosystems. Here, we investigated the potential for ACI and sound pressure level (SPL – another common metric used), to accurately respond to biological sounds on coral reefs when calculated using three different frequency resolutions (31.2 Hz, 15.6 Hz, and 4 Hz). Acoustic recordings were made over two to three-week periods in 2017 and 2018 at sites around Kiritimati (Christmas Island), in the central equatorial Pacific. We hypothesized that SPL would be positively correlated with the number of nearby fish sounds in the low frequency band and with snapping shrimp snaps in the high frequency band, but that ACI would rely on its settings, specifically its frequency resolution, to describe sounds in both frequency bands. We found that nearby fish sounds were partially responsible for changes in low frequency SPL in the morning, during crepuscular chorusing activity, but not at other times of day. Snapping shrimp snaps, however, were responsible for large changes in high frequency SPL. ACI results were reliant on the frequency band chosen, with the 31.2 Hz frequency resolution models being chosen as the best models. In the low frequency band, the effect of fish knocks was positive and significant only in the 31.2 Hz and 15.6 Hz models while in the high frequency band snapping shrimp snaps were negatively associated with ACI in all frequency resolutions. These results contribute to a growing body of evidence against the continued use of ACI without standardization on highly energetic underwater ecosystems like coral reefs and highlight the importance of extensive field testing of new acoustic metrics prior to their adoption and proliferation.

Effect of biological and anthropogenic sound on the orientation behavior of four species of brachyuran crabs

The settlement phase of crustaceans is critical and can ultimately affect their population structure. Underwater sound has been proposed as one of the most important sensory cues used by these animals during this phase because it can provide direction and habitat quality information. Here, we evaluated the effect of different acoustic signals (biological and anthropogenic) on the orientation response of different stages (megalopae and juveniles) of 4 brachyuran crabs (Cyrtograpsus angulatus, C. altimanus, Neohelice granulata, Leptuca uruguayensis) from Mar Chiquita coastal lagoon in Argentina. A binary choice chamber system was used, and different sound sources (crustacean, fish and motorboat signals) selected from recordings of the lagoon soundscape were reproduced. C. angulatus megalopae and juveniles responded positively towards crustacean signals, while juveniles responded negatively towards fish sounds. N. granulata juveniles orientated negatively towards crustacean, motorboat and fish signals. C. altimanus and L. uruguayensis juveniles did not respond to fish signals. The results support the idea that invertebrates can discriminate among conspecific signals and highlight the role of sound on prey-predator relationships. The behavioral orientation response to the motorboat sound evidences a presumably negative effect of anthropogenic sound on the biological interactions of species. This information is important, given the urgent need to increase knowledge about coastal marine lagoons to enhance their protection, especially considering the role of the key species of crabs in this habitat.