Fish Vocalizations Research Articles

Moonlight-driven biological choruses in Hawaiian coral reefs.

Sounds from fish and invertebrates in coral reefs can create persistent cacophonies that can be recorded for ecosystem monitoring, including during nighttime hours where visual surveys are typically not feasible. Here we use soundscape measurements in Hawaii to demonstrate that multiple coral reef communities are rapidly responsive to shifts in nighttime ambient light, with sustained changes in biological sound between moonrise and moonset. High frequency pulse train sounds from fish (0.5-1.5 kHz) are found to increase during moonlight hours, while low frequency fish vocalizations (0.1-0.3 kHz) and invertebrate sounds (2-20 kHz) are found to decrease during moonlight hours. These discoveries suggest that the rising and setting of the moon triggers regular shifts in coral reef ecosystem interactions. Future acoustic monitoring of reef health may be improved by comparing soundscapes during moonlight and non-moonlight hours, which may provide early indicators of shifts in the relative abundance of separate reef communities.

Particle motion polarization of offshore fish vocalizations, boat noise, and ambient soundscapes

Acoustic particle motion is an important acoustic cue for fish and aquatic invertebrate hearing. When reported for bioacoustics applications, it is often described as a magnitude only. However, particle motion is a vector quantity with polarization information (including directionality) relevant to detection and localization of sound cues by fishes and invertebrates. This study applied established metrics of particle motion polarization including ellipse amplitude, angle, orientation, and degree of polarization, to compare sounds of fish vocalizations with that of boat and ambient sounds at a 900 m-deep site (in the Atlantic Deepwater Ecosystem Observatory Network) offshore of Florida. Polarization metrics were computed for bivariate signals in the plane formed by the horizontal source-receiver and vertical axes. Boat sound polarization was quantified at multiple distances from the closest point of approach. Fish and boat sounds had narrower particle motion ellipses and larger amplitudes in the horizontal compared to ambient sounds that were more circular with larger relative vertical amplitudes. Fish and boat sounds were often strongly polarized, which may allow spatial release from masking given sufficient angular separation of sounds. This analysis framework has promising applications for monitoring in situ directionality of fish and other animal vocalizations and for modelling directional masking.

Moonlight driven biological choruses in coral reefs

Sounds from fish and invertebrates in coral reefs can create persistent cacophonies that can be recorded for ecosystem monitoring, including during nighttime hours where visual surveys are typically not feasible. Here, we use soundscape measurements in Hawaii and Bermuda to demonstrate that multiple coral reef communities are rapidly responsive to shifts in nighttime ambient light, with sustained changes in biological sound between moonrise and moonset. Feeding sounds from parrotfish become more prominent as moonlight increases nighttime visibility, and fish vocalizations become less prominent with moonlight, likely to minimize detection during times with increased predation. The response of invertebrate sounds to moonlight varies by location, increasing in Hawaii reefs and decreasing in Bermuda reefs. These discoveries suggest that the rising and setting of the moon triggers regular shifts in coral reef ecosystem interactions. Future acoustic monitoring of reef health may be improved by comparing soundscapes during moonlight and non-moonlight hours, which may provide early indicators of shifts in the relative abundance of separate reef communities.

Vocalizations of two conspecific damselfish (Pomacentridae) at two Australian World Heritage sites: The Ningaloo Coast and the Great Barrier Reef

Novel methods to use Ocean Sound to address ecological questions are increasingly being developed but require optimization and validation to ensure their reliability. Source validation, increasing the number of known soniferous species of marine fauna, and characterizing their acoustic repertoires are important components of this effort. Coral reefs are remarkably complex, diverse, and noisy environments, inhabited by many soniferous species, hindering the association of vocalizations with the emitting species. Damselfish (Pomacentridae) are common and conspicuous reef fishes that have been relatively well-studied due to their abundance, territorial behaviors, and sound production. Most fish sound studies support that fish vocalizations are species-specific, often showing niche acoustic partitioning to avoid competition across frequency and time. It is imperative to record fish vocalizations in the field to avoid distortion in their acoustic attributes, which then can be used for further analyses such as automated detections. Here, we characterize the vocalizations of Dascyllus aruanus and Dascyllus reticulatus using field-experimental settings for in situ recordings from the Ningaloo Coast and the Great Barrier Reef. [Work supported by the BHP-AIMS Australian Coral Reef Resilience Initiative. JCAS was supported by Curtin University and BHP-AIMS in the form of a Curtin Strategic Scholarship and Top-up Scholarship.]

Detection of cetacean and fish sounds using normalized summation of harmonics and spectrogram masking.

There is a growing interest in the ability to detect and classify animal vocalizations in large scale bioacoustic databases for the purposes of conservation and research. To aid in this, two methods are proposed for the quick and accurate detection of harmonic cetacean and fish vocalizations: Normalized summation of sound harmonics and spectrogram masking. These methods utilize a normalization scheme that enables robust performance, achieving 30% more precision and recall than traditional spectrogram cross correlation in the presence of wideband noise and low signal-to-noise ratios. The proposed methods also perform up to 135 times faster than spectrogram cross correlation.

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.

The coastal Arctic marine soundscape near Ulukhaktok, Northwest Territories, Canada

The soundscape is an important habitat feature for marine animals, and climate change may cause large changes to the Arctic marine soundscape through sea ice loss and increased anthropogenic activity. We examined the marine soundscape over eight months near Ulukhaktok, Northwest Territories, Canada, and assessed the relative contribution of the geophony (wind and wave sounds), biophony (marine mammal and fish sounds), and anthrophony (noise from vessel traffic). Sound pressure levels (SPL) were significantly higher during the summer than during the autumn and winter, and these differences were caused by increased wind/waves and vessel traffic in the summer. Increased wind speed drove increased SPL, while increased ice concentration resulted in decreased SPL. When vessel traffic was closer, SPL was higher. Marine mammal and fish vocalizations did not influence SPL; however, timing of vocalizations of both whales and seals matched seasonal patterns shown in other studies within the region. Overall, the marine soundscape near Ulukhaktok varied greatly through time and may be prone to large changes in the future as the ice-free season continues to lengthen and more vessels travel through the region.

Soundscapes indicate kelp forest condition

Soundscapes are promising indicators of marine habitat condition, yet this approach remains untested in many ecosystems, and soundscape-ecological relationships remain unclear. In this study, we analyzed soundscapes in kelp forest habitats off the coast of California, USA, in Channel Islands National Park. We investigated if (1) soundscape features correlated with ecological variables and (2) these features differed inside and outside of marine protected areas (MPAs). We recorded 1 min every 15 min at 5 sites from 12 May to 23 June 2018. Three sites were in MPAs with high kelp cover and low urchin density, while 2 were in adjacent, unprotected habitats with low kelp cover and high urchin density. To analyze the data, we calculated soundscape features using detection algorithms and acoustic indices, which we then correlated with annual ecological data from 2016 to 2018. We found that drivers of regime shifts in kelp forests, i.e. sea urchin density, kelp cover, and fish diversity, were significantly related to soundscape features. Sea urchin density was positively correlated and kelp cover negatively correlated with the rate of shrimp snaps. Fish species richness and abundance were positively correlated with the intensity and diel dynamics in the low-frequency bands that contained most fish vocalizations. This study demonstrates that marine soundscapes indicate the condition of kelp forests, which are vulnerable to destruction from urchin overgrazing. If marine soundscapes can reliably indicate the status of ecological drivers, then this approach could be a valuable complement to diver surveys in fully assessing marine ecosystem health.

Effect of broadband chirp signal on the sonic behavior of the /kwa/ fishes inhabiting Posidonia oceanica seagrass meadow

Early experiment to study acoustics of Posidonia oceanica seagrasses (USTICA99) transmitted acoustic chirp signals (0.2-16 kHz, 15.8 s) every minute during 3 days over a meadow. Receiving hydrophones recorded vocalizations from unknown fish inhabitants, which sound like /kwa/. Here, we address the impact of our measurements on this fish population. The authors’ ears analyzed the recordings to identify all fish vocalizations and attempt to recognize /kwa/ individuals based on timbre. A comparative analysis of the /kwa/ sound production within time intervals between and during chirp transmission was made to understand if and how the sonic behavior is affected. As in few similar studies for other anthropogenic noise sources on a limited number of species, there was an observable effect. The major part of the vocalization patterns that were identified within the chirp time interval started near the onset of the frequency sweep, which first spans the range of /kwa/ sound production (0.4-2 kHz). The number of single vocalizations per unit time during that period was close to that during the no-chirp time interval while during higher swept frequencies was markedly smaller. This suggests the fish detection range may extend toward ultrasound to avoid dolphin predators. Quantitative results will be presented.

Marine soundscape as an additional biodiversity monitoring tool: A case study from the Adriatic Sea (Mediterranean Sea)

Acoustic monitoring can provide essential information on marine environments, including insights into ecosystem functioning and marine biodiversity monitoring. However, data on species acoustic behavior and ecoacoustics studies in the Mediterranean Sea are still extremely scarce and this limits our ability to use soundscape features in monitoring studies. Here we present the results of a soundscape investigation conducted on shallow hard bottoms of the Adriatic Sea (Central Mediterranean basin). We report the presence of diverse circadian rhythms recorded in two different months, July and September. A power spectral density (PSD) was used to assess the overall spectral composition over time, and the Acoustic Complexity Index (ACI), was identified as a proxy for marine sounds of biological origin. The dominant component of the biological soundscape was composed of snapping shrimps and fishes. Spectral characteristics varied significantly both daily and between the two months. For frequencies >620Hz (i.e., associated to snapping shrimp activity), both PSD and ACI were higher in July than in September. The same circadian rhythm was reported in both sampling periods, with the presence of snaps for 24h a day, but with significantly lower intensity during daylight hours and pitches at the beginning and ending of the night. At lower frequencies (i.e., <620Hz), fish vocalizations mostly occurred during the night. Higher values of ACI were recorded during the night in both months, whereas the presence of anthropogenic noise caused opposite results in PSD levels. Noise was associated with higher PSD and ACI at the peak frequency of the snaps, suggesting a stimulation in snapping activity. Our findings provide new insights on the marine biological soundscape and on the potential use of ecoacoustics in future monitoring programs.

Automatic Taxonomic Classification of Fish Based on Their Acoustic Signals

Fish as well as birds, mammals, insects and other animals are capable of emitting sounds for diverse purposes, which can be recorded through microphone sensors. Although fish vocalizations have been known for a long time, they have been poorly studied and applied in their taxonomic classification. This work presents a novel approach for automatic remote acoustic identification of fish through their acoustic signals by applying pattern recognition techniques. The sound signals are preprocessed and automatically segmented to extract each call from the background noise. Then, the calls are parameterized using Linear and Mel Frequency Cepstral Coefficients (LFCC and MFCC), Shannon Entropy (SE) and Syllable Length (SL), yielding useful information for the classification phase. In our experiments, 102 different fish species have been successfully identified with three widely used machine learning algorithms: K-Nearest Neighbors (KNN), Random Forest (RF) and Support Vector Machine (SVM). Experimental results show an average classification accuracy of 95.24%, 93.56% and 95.58%, respectively.

Acoustic habitat of an oceanic archipelago in the Southwestern Atlantic

Underwater soundscapes can be highly variable, and in natural conditions are often dominated by biological signals and physical features of the environment. Few studies, however, focused on oceanic islands soundscapes. Islands in the middle of ocean basins can provide a good example of how untouched marine soundscapes are. Autonomous acoustic recordings were carried out in two different seasons in Trindade-Martin Vaz Archipelago, Southwestern Atlantic, providing nearly continuous data for both periods. Sound levels varied daily and between seasons. During summer, higher frequencies were noisier than lower frequencies, with snapping shrimp being the dominating sound source. During winter, lower frequencies were noisier than higher frequencies due to humpback whale constant singing. Biological signal detection had a marked temporal pattern, playing an important role in the soundscape. Over 1000 humpback whale sounds were detected hourly during winter. Fish vocalizations were detected mostly during night time during both summer and winter. The results show an acoustic habitat dominated by biological sound sources and highlight the importance of the island to humpback whales in winter.

Identification of fish vocalizations from ocean acoustic data

Abstract A new method for identification of fish vocalizations based on auditory analysis and support vector machine (SVM) classification is presented. In this method, high resolution features have been extracted from fish vocalization data using the amplitude modulation spectrogram (AMS) of the input signals to facilitate the identification of grunts and growls made by a highly vocal wild fish, Porichthys notatus. The comparison results made from ocean audio recordings verify the effectiveness of the proposed method in identifying various types of fish vocalizations. The relationships between signal-to-noise ratio (SNR) and ocean temperature with the accuracy of the proposed method have also been quantified. Moreover, a context-aware prediction algorithm is introduced for estimating the continuous data.

Does Masking Matter? Shipping Noise and Fish Vocalizations.

Shipping creates large near-field background noises at levels similar to or higher than fish vocalizations and in the same critical bandwidths. This noise has the potential to "mask" biologically important signals and prevent fish from hearing them; any interference with the detection and recognition of sounds may impact fish survival. The Lombard effect, whereby vocalizations are altered to reduce or exclude masking effects, is an adaptation that has been observed in mammals and birds. Research is needed to establish whether the Lombard effect occurs in fish to gain a better understanding of the implications of noise pollution on fish populations.

Call recognition and individual identification of fish vocalizations based on automatic speech recognition: An example with the Lusitanian toadfish.

The study of acoustic communication in animals often requires not only the recognition of species specific acoustic signals but also the identification of individual subjects, all in a complex acoustic background. Moreover, when very long recordings are to be analyzed, automatic recognition and identification processes are invaluable tools to extract the relevant biological information. A pattern recognition methodology based on hidden Markov models is presented inspired by successful results obtained in the most widely known and complex acoustical communication signal: human speech. This methodology was applied here for the first time to the detection and recognition of fish acoustic signals, specifically in a stream of round-the-clock recordings of Lusitanian toadfish (Halobatrachus didactylus) in their natural estuarine habitat. The results show that this methodology is able not only to detect the mating sounds (boatwhistles) but also to identify individual male toadfish, reaching an identification rate of ca. 95%. Moreover this method also proved to be a powerful tool to assess signal durations in large data sets. However, the system failed in recognizing other sound types.

Brown meagre vocalization rate increases during repetitive boat noise exposures: A possible case of vocal compensation

This study investigated whether or not boat noise causes variations in brown meagre (Sciaena umbra) vocalizations recorded in a nearshore Mediterranean marine reserve. Six nocturnal experimental sessions were carried out from June to September 2009. In each of them, a recreational boat passed over vocalizing fish 6 times with 1 boat passage every 10 min. For this purpose three different boats were used in random order: an 8.5-m cabin-cruiser (CC), a 5-m fiberglass boat (FB), and a 7-m inflatable boat (INF). In situ continuous acoustic recordings were collected using a self-standing sonobuoy. Because boat noise levels largely exceeded both background noise and S. umbra vocalizations in the species' hearing frequency range, masking of acoustic communication was assumed. Although no immediate effect was observed during a single boat passage, the S. umbra mean pulse rate increased over multiple boat passages in the experimental condition but not in the control condition, excluding that the observed effect was due to a natural rise in fish vocalizations. The observed vocal enhancement may result either from an increased density of callers or from an increased number of pulses/sounds produced by already acoustically active individuals, as a form of vocal compensation. These two explanations are discussed.

Use of an implanted sound recording device (Bioacoustic Probe) to document the acoustic environment of a blacktip reef shark (Carcharhinus melanopterus)

Gaps in our knowledge of basic fish have provided impetus for development of novel ecology to detect and quantify hard to observe behaviors such as spawning, schooling and feeding. The acoustic envi- ronment is one source of potentially useful information about these behaviors. We implanted an acoustic recording tag (Bioacoustic Probe) into the gut cavity of a blacktip reef shark to determine whether an implanted tag could success- fully record external and internal sounds. The tag successfully recorded reef fish vocalizations, boat engine noise, the sound of the shark feeding and unidentified rhythmic sounds that may derive from shark tail beats. Technical challenges remain, but sound recording tags have the potential to provide novel insights into shark and fish ecology.