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An invasive predator eradication campaign is planned for 2024 on Amsterdam Island, one of world's top priority island for seabird conservation. In order to monitor the effects on seabird colonies post-eradication, a survey of burrow-nesting species and population monitoring of albatrosses, penguins, skuas and terns was organised pre-eradication. Several counting techniques and acoustic methods were used to infer presence/absence of burrow-nesting species and to estimate abundance of other species, as well as genetic methods for species identification. In total 14 breeding (or probably breeding) seabird species were detected on Amsterdam Island, among which eight burrowing petrels including two species never described on the island: the Juan Fernandez petrel Pterodroma externa and the sooty sherwater Ardenna grisea. Based on these new data, the introduced mammal eradication campaign on Amsterdam, if successful, will likely be extremely beneficial for seabird conservation, and may also favor the colonization of Amsterdam by new seabird species. [ABSTRACT FROM AUTHOR]

Although the presence of the golden jackal (Canis aureus moreoticus) in Italy has been documented since 1984, it has long been considered an accidental species confined to a limited portion of the northeastern sector of the country. Recently, dispersing individuals of golden jackal have been reported in different areas of northern Italy, suggesting an enhanced spreading attitude compared to the past. However, despite a wider covered area, no evidence of reproductive groups south of the Po River has ever been documented, suggesting possible geographical limitations due to the habitat or ecological conditions. This study witnesses the overcoming of this large freshwater course by the species, and describes the first reproductive group of golden jackals south of Po River in a context of a highly industrialized area. The results are obtained using different methods (citizen science, howling, camera trapping, search of signs) able to demonstrate an expansion of this mesocarnivore outside its traditional northeastern Italian distribution range. Interesting questions are also raised about the species ecology with special regard to its southern migration pattern through anthropic zones. [ABSTRACT FROM AUTHOR]

The abundance of gelatinous organisms, such as salps and jellyfish, in the Adriatic Sea has significantly increased over the past decade. Environmental factors play a key role in driving this shift in abundance through rising temperatures and a consequent decrease in oxygen levels in the water, for which jellyfish have higher tolerance levels. Additionally, fisheries may contribute to the proliferation of jellyfish by diminishing their natural predators and food competitors. Pelagic trawl catch data from 2015 to 2023 acquired during MEDIAS acoustic surveys in the western Adriatic Sea were reviewed to extract information concerning the abundance and distribution of salps and jellyfish. These data were subsequently analyzed and compared with satellite environmental information to identify potential correlations. When considering environmental information related to the month of the survey, the results show two significant relationships: one between the abundance of Aequorea aequorea and average salinity and another one between the abundance of Rhizostoma pulmo and bottom temperature. Furthermore, when considering environmental data from the month preceding the survey, a relationship between the overall abundance of gelatinous organisms, salps and jellyfish together, and surface temperature was identified. Additionally, an analysis was conducted on specific hauls that almost exclusively yielded jellyfish, with the aim of identifying their echo traces. Although it was not possible to allocate one jellyfish species to a specific echo trace due to the frequent co-occurrence of more than one species, a general indication of typical backscatter for these species, with a higher response at 70 kHz, was consistently observed in all cases examined. [ABSTRACT FROM AUTHOR]

This study used a multi-frequency acoustic method to assess the density and spatial distribution of dominant zooplankton, euphausiids and copepods, which are representative species of the zooplankton immigrating the sea around Republic of Korea. Acoustic surveys were carried out in the East Sea and South Sea from June 16 to 29, 2017, using the research vessel Tamgu 20th from the National Institute of Fisheries Science. From the results of the acoustic survey, the distribution of euphausiids was relatively higher in the East Sea than in the South Sea. Additionally, although the distribution of copepods was low in all areas, they were abundant in certain areas in the East Sea and the southern area of the Jeju Sea. Euphausiid and copepod density was estimated to be 1.2 g/m2 (CV = 19.1%) and 2.8 g/m2 (CV = 23.5%), respectively.

Primate population density often varies considerably between sites, reflecting differences in site conditions and resource availability. Understanding these differences may provide important insights for habitat management. We identified environmental variables that affect the population density of Callicebus coimbrai in forest patches throughout its geographic distribution in northeastern Brazil. We sampled the vegetation structure of 19 forest patches and assessed the composition of the surrounding landscape and the resistance of the surrounding matrix to the movement of C. coimbrai. We used the number of responses of C. coimbrai to playback to estimate the species density in each patch. The density of C. coimbrai was positively related to understory vegetation density, and tree diameter and density, but not to the surrounding landscape composition. The sites with the highest densities were concentrated in the center of the species geographic range and only one of the forest patches may be large enough to host a viable population of C. coimbrai over the long term. Denser understories and larger and closed-spaced trees were related to food availability, and possibly also to predator avoidance, although most predators were extirpated from the region. C. coimbrai tolerate and may even benefit from forest disturbance, depending on how the process has changed the vegetation structure. Our results emphasize the need to enhance the connectivity of the forest patches, particularly in the central portion of the species distribution. Our findings suggest that a whole-range approach is effective to identify the drivers of species density, and priority areas and conservation strategies. [ABSTRACT FROM AUTHOR]

Echolocation call descriptions of local bat species in the Philippines have been published recently. However, collected reference call data has been biased towards species that can easily be captured using mist nets and harp traps, whereas acoustic data for rare and aerial species that are less frequently recorded by traditional means remain absent. Significant gaps still exist in our knowledge about the distribution, ecology, behavior, and population of most of these high-flying bats in the Philippines. In this study, we report new locality records and provide an echolocation call description for Saccolaimus saccolaimus, a locally rare bat species with only a few known records from the Philippines. Three localities surveyed represent new distributional records for this species in the Philippines: La Union and Bulacan in Luzon Island, and Davao City in Mindanao Island. Echolocation calls of this species are mainly characterized by pulses of long multi-harmonic calls, which are emitted at ca. 20 kHz, the lowest frequency recorded thus far among Philippine bats. Our data contributes to understanding this species' distribution and preference for modified habitats and residential areas, as well as to providing reference call data for future acoustic surveys and monitoring of this rare bat species. [ABSTRACT FROM AUTHOR]

The abundance of gelatinous organisms, such as salps and jellyfish, in the Adriatic Sea has significantly increased over the past decade. Environmental factors play a key role in driving this shift in abundance through rising temperatures and a consequent decrease in oxygen levels in the water, for which jellyfish have higher tolerance levels. Additionally, fisheries may contribute to the proliferation of jellyfish by diminishing their natural predators and food competitors. Pelagic trawl catch data from 2015 to 2023 acquired during MEDIAS acoustic surveys in the western Adriatic Sea were reviewed to extract information concerning the abundance and distribution of salps and jellyfish. These data were subsequently analyzed and compared with satellite environmental information to identify potential correlations. When considering environmental information related to the month of the survey, the results show two significant relationships: one between the abundance of Aequorea aequorea and average salinity and another one between the abundance of Rhizostoma pulmo and bottom temperature. Furthermore, when considering environmental data from the month preceding the survey, a relationship between the overall abundance of gelatinous organisms, salps and jellyfish together, and surface temperature was identified. Additionally, an analysis was conducted on specific hauls that almost exclusively yielded jellyfish, with the aim of identifying their echo traces. Although it was not possible to allocate one jellyfish species to a specific echo trace due to the frequent co-occurrence of more than one species, a general indication of typical backscatter for these species, with a higher response at 70 kHz, was consistently observed in all cases examined.

Abstract Passive acoustic monitoring of biodiversity is growing fast, as it offers an alternative to traditional aural point count surveys, with the possibility to deploy long‐term acoustic surveys in large and complex natural environments. However, there is still a clear need to evaluate how the frequency‐ and distance‐dependent attenuation of sound as well as the ambient sound level impact the acoustic detection distance of the soniferous species in natural environments over the diel cycles and across seasons. This is of great importance to avoid pseudoreplication and to provide relevant biodiversity indicators, including species richness, species abundance and species density. To address the issue of detection distance, we tested a field‐based protocol in a Neotropical rainforest (French Guiana, France) and in an Alpine coniferous forest (Jura, France). This standardized and repeatable method consists in a recording session of the ambient sound directly followed by an experiment using a calibrated white noise sound broadcast at different positions along a 100 m linear transect. We then used acoustic laws to reveal the basic physics behind sound propagation attenuation. We demonstrate that habitat attenuation in two different kinds of forests can be modelled by an exponential decay law with a linear dependence on frequency and distance. We also report that habitat attenuation, as first approximation, can be summarized by a single value, the coefficient of attenuation of the habitat. Finally, we show that the detection distance can be predicted knowing the contribution of each attenuation factor, the coefficient of attenuation of the habitat, the ambient sound pressure level and the amplitude and frequency bandwidth characteristics of the transmitted sound. We show that the detection distance mostly depends on the ambient sound and may vary by a factor of up to 5 over the diel cycle and across seasons. These results reinforce the need to take into account the variation of the detection distance when performing passive acoustic surveys and producing reliable biodiversity indicators.

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Passive acoustic monitoring of biodiversity is growing fast, as it offers an alternative to traditional aural point count surveys, with the possibility to deploy long‐term acoustic surveys in large and complex natural environments. However, there is still a clear need to evaluate how the frequency‐ and distance‐dependent attenuation of sound as well as the ambient sound level impact the acoustic detection distance of the soniferous species in natural environments over the diel cycles and across seasons. This is of great importance to avoid pseudoreplication and to provide relevant biodiversity indicators, including species richness, species abundance and species density.To address the issue of detection distance, we tested a field‐based protocol in a Neotropical rainforest (French Guiana, France) and in an Alpine coniferous forest (Jura, France). This standardized and repeatable method consists in a recording session of the ambient sound directly followed by an experiment using a calibrated white noise sound broadcast at different positions along a 100 m linear transect. We then used acoustic laws to reveal the basic physics behind sound propagation attenuation.We demonstrate that habitat attenuation in two different kinds of forests can be modelled by an exponential decay law with a linear dependence on frequency and distance. We also report that habitat attenuation, as first approximation, can be summarized by a single value, the coefficient of attenuation of the habitat.Finally, we show that the detection distance can be predicted knowing the contribution of each attenuation factor, the coefficient of attenuation of the habitat, the ambient sound pressure level and the amplitude and frequency bandwidth characteristics of the transmitted sound. We show that the detection distance mostly depends on the ambient sound and may vary by a factor of up to 5 over the diel cycle and across seasons. These results reinforce the need to take into account the variation of the detection distance when performing passive acoustic surveys and producing reliable biodiversity indicators. [ABSTRACT FROM AUTHOR]

Due to global agricultural expansion and intensification, many animal species must now survive within a landscape dominated by agroecosystems. For bats, agroecosystems can provide a valuable foraging-habitat, and many species of bats thrive within such habitats whilst also providing a range of ecosystem services for farmers. Despite this, bat usage of many agroecosystem types remains unstudied. Here, we investigated the diversity of insectivorous bats in the vanilla agroecosystems of northeastern Madagascar, the world's principal vanilla-growing region. To assess bat diversity, we used a passive acoustic survey technique, and we identified and classified bat species diversity using PCA and DFA analysis of echolocation call acoustic parameters. In total, we were able to detect the presence of at least 13 different bat species within Madagascar's vanilla agroecosystems, seven of which we were able to confidently identify to species level. However, due to our conservative classification approach, the true diversity of bats in vanilla agroecosystems is likely to be higher. The results of this study indicate that Madagascar's vanilla agroecosystems represent suitable foraging habitat for numerous bat species, particularly forest-specialists, which is a highly encouraging finding for the conservation of Madagascar's bats. Expansion of vanilla agroecosystems is therefore likely to provide valuable habitat extensions for Madagascar's forest bats in the future, provided this expansion does not come at the expense of existing largely-undisturbed natural habitats. [ABSTRACT FROM AUTHOR]

Manually annotating audio files for bird species richness estimation or machine learning validation is a time‐intensive task. A premium is placed on the subselection of files that will maximize the efficiency of unique additional species identified, to be used for future analyses. Using acoustic data collected in 17 plots, we created 60 subsetting scenarios across three gradients: intensity (minutes in an hour), day phase (dawn, morning, or both), and duration (number of days) for manual annotation. We analyzed the effect of these variables on observed bird species richness and assemblage composition at both the local and entire study area scale. For reference, results were also compared to richness and composition estimated by the traditional point count method. Intensity, day phase, and duration all affected observed richness in decreasing respective order. These variables also significantly affected observed assemblage composition (in the same order of effect size), but only the day phase produced compositional dissimilarity that was due to phenological traits of individual bird species, rather than differences in species richness. All annotation scenarios requiring equal sampling effort to point counts yielded higher species richness than the point count method. Our results show that a great majority of species can be obtained by annotating files at high sampling intensities (every 3 or 6 min) in the morning period (post‐dawn) over a duration of two days. Depending on a study's aim, different subsetting parameters will produce different assemblage compositions, potentially omitting rare or crepuscular species, species representing additional functional groups and natural history guilds, or species of higher conservation concern. We do not recommend one particular subsetting regime for all research objectives, but rather present multiple scenarios for researchers to understand how intensity, day phase, and duration interact to identify the best subsetting regime for one's particular research interests. [ABSTRACT FROM AUTHOR]

In this study, the distribution of giant N. jellyfish by the echo counting method was investigated in the East China Sea, where giant N. jellyfish are known to breed and migrate to the coastal waters of Korea mainly in summer. In addition, the distribution densities by the survey method were compared with the sighting and trawl surveys. In the case of the East China Sea area and the Gijang coastal area, a split beam type scientific echosounder (EK60, Simrad, Norway) and Acoustic data at 38 and 120 kHz were collected while moving at 6–7 kts. In the coastal waters of Korea, acoustics data at 38 and 120 kHz were collected with a split beam type scientific echosounder (EK80, Simrad, Norway) attached to the bottom of the R/V Tamgu No. 21. In the East China Sea, the average distribution densities of acoustic, sighting, and trawl surveys were 8355.7 (10−6 ind/m3), 162.2 (10−6 ind/m3), and 792.5 (10−6 ind/m3), respectively. The average densities in the coastal waters of Korea of acoustic, sighting, and trawl surveys were 2238.7 (10−6 ind/m3), 664.9 (10−6 ind/m3), and 432.9 (10−6 ind/m3), respectively. The average distribution density of the acoustic survey conducted on 21 July 2020 in the coastal waters of Gijang was 1024.5 (10−6 ind/m3), and the sighting survey showed 48.8 (10−6 ind/m3). The sighting surveys conducted on 22 July 2020 were 393.3 (10−6 ind/m3) and 19.6 (10−6 ind/m3). The average distribution density for the acoustic survey performed on 23 July 2020 was 99.0 (10−6 ind/m3), and for the sighting survey was 197.2 (10−6 ind/m3). When comparing the results of the acoustic survey with the results of the sighting and the trawl surveys, all surveys except for the survey conducted on 23 July 2020 showed that the acoustic survey was higher than other survey methods. [ABSTRACT FROM AUTHOR]

Six specimens of Bregmaceros nectabanus were collected during the acoustic survey MEDIAS in two consecutive years, off Termoli (Italy) in 2020 and in Albanian waters in 2021, during two night shallow hauls. We report the northernmost record of the alien species in the Mediterranean Sea (Northern Adriatic Sea, FAO fishing area 37.2.1) and one of the highest number of individuals caught in a single haul. This finding testifies a recent geographical spread to the eastern Mediterranean Sea from its distribution area in the Indo-Pacific Ocean and Red Sea, reaching the Adriatic Sea during the 2019. Our records support the hypothesis of a possible establishment of B. nectabanus in this basin. [ABSTRACT FROM AUTHOR]

Abstract Manually annotating audio files for bird species richness estimation or machine learning validation is a time‐intensive task. A premium is placed on the subselection of files that will maximize the efficiency of unique additional species identified, to be used for future analyses. Using acoustic data collected in 17 plots, we created 60 subsetting scenarios across three gradients: intensity (minutes in an hour), day phase (dawn, morning, or both), and duration (number of days) for manual annotation. We analyzed the effect of these variables on observed bird species richness and assemblage composition at both the local and entire study area scale. For reference, results were also compared to richness and composition estimated by the traditional point count method. Intensity, day phase, and duration all affected observed richness in decreasing respective order. These variables also significantly affected observed assemblage composition (in the same order of effect size), but only the day phase produced compositional dissimilarity that was due to phenological traits of individual bird species, rather than differences in species richness. All annotation scenarios requiring equal sampling effort to point counts yielded higher species richness than the point count method. Our results show that a great majority of species can be obtained by annotating files at high sampling intensities (every 3 or 6 min) in the morning period (post‐dawn) over a duration of two days. Depending on a study's aim, different subsetting parameters will produce different assemblage compositions, potentially omitting rare or crepuscular species, species representing additional functional groups and natural history guilds, or species of higher conservation concern. We do not recommend one particular subsetting regime for all research objectives, but rather present multiple scenarios for researchers to understand how intensity, day phase, and duration interact to identify the best subsetting regime for one's particular research interests.

The subjective judgment on the annoyance produced by noise is always an important tool to complete an investigation, and to find the best way for its reduction. Therefore, acoustic analyses for environmental improvement frequently combine objective measures with subjective surveys to gain a comprehensive understanding of the problem. The technical specification, concerning the “Assessment of noise annoyance by means of social and socio-acoustic surveys”, ISO/TS 15666 (revised in 2021), has represented a basis for these activities since 2003, when it aimed to obtain information about noise annoyance “at home”. The more recent ISO/TS 12913-2 (2018), aimed at soundscape studies, investigations and applications, provides guidelines for conducting social and socio-acoustic surveys to assess noise annoyance and, in particular, it gives detailed indications on data collection and reporting. The indications provided by the technical specifications represent a common guideline for addressing the implementation of a subjective survey in the acoustic field, and to make investigations as comparable as possible. However, they do not cover all the fields of acoustic subjective investigations. Therefore, to make the collection of information from questionnaires more effective, it is useful to have a broader review of the issues that need to be addressed. To support this type of activity, this paper collects and presents relevant observations for the design of subjective survey questionnaires focused on outdoor acoustic quality. Drawing on previous research studies and experiences, it provides a series of observations on the main aspects to be considered in order to structure multipurpose acoustic evaluation questionnaires, including discussion of the general considerations for questionnaire structure, administration methods, population sample characterization, question formulation, and classification. It also deals with specific indications related to acoustic evaluations, such as the characteristics of annoying noise, boundary conditions, subjective feelings, and source features.

Passive acoustic surveys are becoming increasingly popular as a means of surveying for cetaceans and other marine species. These surveys yield large amounts of data, the analysis of which is time consuming and can account for a substantial proportion of the survey budget. Semi‐automatic processes enable the bulk of processing to be conducted automatically while allowing analyst time to be reserved for validating and correcting detections and classifications.Existing modules within the Passive Acoustic Monitoring software PAMGuard were used to process a large (25.4 Terabyte) dataset collected during towed acoustic ship transits. The recently developed 'Multi‐Hypothesis Tracking Click Train Detector' and the 'Whistle and Moan Detector' modules were used to identify occasions within the dataset at which vocalising toothed whales (odontocetes) were likely to be acoustically present. These putative detections were then reviewed by an analyst, with false positives being corrected. Target motion analysis provided a perpendicular distance to odontocete click events enabling the estimation of detection functions for both sperm whales and delphinids. Detected whistles were assigned to the lowest taxonomical level possible using the PAMGuard 'Whistle Classifier' module.After an initial tuning process, this semi‐automatic method required 91 hr of an analyst's time to manually review both automatic click train and whistle detections from 1,696 hr of survey data. Use of the 'Multi‐Hypothesis Tracking Click Train Detector' reduced the amount of data for the analyst to search by 74.5%, while the 'Whistle and Moan Detector' reduced data to search by 85.9%. In total, 443 odontocete groups were detected, of which 55 were from sperm whale groups, six were from beaked whales, two were from porpoise and the remaining 380 were identified to the level of delphinid group. An effective survey strip half width of 3,277 and 699 m was estimated for sperm whales and delphinids respectively.The semi‐automatic workflow proved successful, reducing the amount of analyst time required to process the data, significantly reducing overall project costs. The workflow presented here makes use of existing modules within PAMGuard, a freely available and open‐source software, readily accessible to acoustic analysts. [ABSTRACT FROM AUTHOR]

When recorders are used to survey acoustically conspicuous species, identification calls of the target species in recordings is essential for estimating density and abundance. We investigate how well deep neural networks identify vocalisations consisting of phrases of varying lengths, each containing a variable number of syllables. We use recordings of Hainan gibbon Nomascus hainanus vocalisations to develop and test the methods.We propose two methods for exploiting the two‐level structure of such data. The first combines convolutional neural network (CNN) models with a hidden Markov model (HMM) and the second uses a convolutional recurrent neural network (CRNN). Both models learn acoustic features of syllables via a CNN and temporal correlations of syllables into phrases either via an HMM or recurrent network. We compare their performance to commonly used CNNs LeNet and VGGNet, and support vector machine (SVM). We also propose a dynamic programming method to evaluate how well phrases are predicted. This is useful for evaluating performance when vocalisations are labelled by phrases, not syllables.Our methods perform substantially better than the commonly used methods when applied to the gibbon acoustic recordings. The CRNN has an F‐score of 90% on phrase prediction, which is 18% higher than the best of the SVM or LeNet and VGGNet methods. HMM post‐processing raised the F‐score of these last three methods to as much as 87%. The number of phrases is overestimated by CNNs and SVM, leading to error rates between 49% and 54%. With HMM, these error rates can be reduced to 0.4% at the lowest. Similarly, the error rate of CRNN's prediction is no more than 0.5%.CRNNs are better at identifying phrases of varying lengths composed of a varying number of syllables than simpler CNN or SVM models. We find a CRNN model to be best at this task, with a CNN combined with an HMM performing almost as well. We recommend that these kinds of models are used for species whose vocalisations are structured into phrases of varying lengths. [ABSTRACT FROM AUTHOR]

Surveying cryptic, sparsely distributed taxa using autonomous recording units, although cost‐effective, provides imperfect knowledge about species presence. Summertime bat acoustic surveys in North America exemplify the challenges with characterizing sources of uncertainty: observation error, inability to census populations, and natural stochastic variation. Statistical uncertainty, if not considered thoroughly, hampers determining rare species presence accurately and/or estimating rangewide status and trends with suitable precision. Bat acoustic data are processed using an automated workflow in which proprietary or open‐source algorithms assign a species label to each recorded high‐frequency echolocation sequence. A false‐negative occurs, if a species is actually present but not recorded and/or all recordings from the species are of such poor quality that a correct species identity cannot be assigned to any observation. False positives for a focal species are a direct result of the presence and incorrect identification of a recording from another species. We compare four analytical approaches in terms of parameter estimation and their resulting (in)correct decisions regarding species presence or absence using realistic data‐generating scenarios for bat acoustic data within a simulation study. The current standard for deciding species presence or absence uses a multinomial likelihood‐ratio test p value (maximum likelihood estimate [MLE]‐metric) that accounts for known species misidentifications, but not imperfect detection and only returns a binary outcome (evidence of presence or not). We found that the MLE‐metric had estimated median correct decisions less than 60% for presence and greater than 85% for absence. Alternatively, a multispecies count detection model was equivalent to or better than the MLE‐metric for correct claims of rare species presence or absence using the posterior probability a species was present at a site and, importantly, provided unbiased estimates of relative activity and probability of occurrence, creating opportunities for reducing posterior uncertainty through the inclusion of meaningful covariates. Single‐species occupancy models with and without false‐positive detections removed were insufficient for determining local presence because of substantially biased occurrence and detection probabilities. We propose solutions to potential barriers for integrating local, short‐term and rangewide, long‐term acoustic surveys within a cohesive statistical framework that facilitates determining local species presence with uncertainty concurrent with estimating species–environment relationships. [ABSTRACT FROM AUTHOR]

Coastal areas have traditionally been difficult locations to collect consistent, high-resolution bathymetric data via vessel-based acoustic surveys. The use of phase-measuring sidescan sonar is becoming more prevalent, particularly in shallow (< 20 m) coastal waters. Instruments used in the field over the last decade by the lead author are discussed here. This work is intended to serve as an introduction to the coastal scientist interested in the operation, use, and data sets associated with these instruments. Hydrographers unfamiliar with phase-measuring sidescan sonar will also benefit from insights regarding survey planning, data acquisition, and processing. These instruments collect co-located sidescan backscatter and swath bathymetry. The effective bathymetric swath widths can be 2 to 3 times that of multibeam echosounders making phase-measuring sidescan sonars ideal for shallow water mapping operations. These large effective swath widths offset the high levels of noise and processing needed in these bathymetric data sets relative to multibeam data. The sidescan backscatter and bathymetric data sets can be used individually, but the co-location allows for uses and analyses not feasible with other data sets. These instruments are well-suited to collect data for a suite of seafloor mapping projects and science-based investigations. Examples from a wide range of projects are detailed here for the shallow water mapping community and the multi-disciplinary groups who may benefit from the data and insights presented here. [ABSTRACT FROM AUTHOR]

Out of the four Molossidae species from South Asia, the distribution of the European free-tailed bat, T. teniotis is most poorly known. This species has been occasionally reported from Afghanistan, Bangladesh, Bhutan, and India; however, no records exist in Nepal. Here we report the first record of T. teniotis from Nepal and comment on its possible elevational movement in the Himalaya. Active acoustic surveys were conducted in the Kali Gandaki canyon during autumn and winter seasons at two elevational zones, 800–1200 m and 2100–2500 m, in three habitat types (forest, agricultural land, and human settlements). Echolocation calls of T. teniotis were easily distinguished by their low frequency, shallow frequency modulation, and long duration. During autumn, the activity was recorded only at 2100 to 2500 m and varied significantly from winter activity, while T. teniotis was observed at both elevational zones during winter. The result confirms the presence of T. teniotis from Nepal. Based on our observations of differential activity at different elevation zones in two seasons, we recommend more intensive studies to confirm seasonal migration and to understand seasonal demographics along the Kali Gandaki landscape and in the entire Himalayan range at large.

Abstract Surveying cryptic, sparsely distributed taxa using autonomous recording units, although cost‐effective, provides imperfect knowledge about species presence. Summertime bat acoustic surveys in North America exemplify the challenges with characterizing sources of uncertainty: observation error, inability to census populations, and natural stochastic variation. Statistical uncertainty, if not considered thoroughly, hampers determining rare species presence accurately and/or estimating rangewide status and trends with suitable precision. Bat acoustic data are processed using an automated workflow in which proprietary or open‐source algorithms assign a species label to each recorded high‐frequency echolocation sequence. A false‐negative occurs, if a species is actually present but not recorded and/or all recordings from the species are of such poor quality that a correct species identity cannot be assigned to any observation. False positives for a focal species are a direct result of the presence and incorrect identification of a recording from another species. We compare four analytical approaches in terms of parameter estimation and their resulting (in)correct decisions regarding species presence or absence using realistic data‐generating scenarios for bat acoustic data within a simulation study. The current standard for deciding species presence or absence uses a multinomial likelihood‐ratio test p value (maximum likelihood estimate [MLE]‐metric) that accounts for known species misidentifications, but not imperfect detection and only returns a binary outcome (evidence of presence or not). We found that the MLE‐metric had estimated median correct decisions less than 60% for presence and greater than 85% for absence. Alternatively, a multispecies count detection model was equivalent to or better than the MLE‐metric for correct claims of rare species presence or absence using the posterior probability a species was present at a site and, importantly, provided unbiased estimates of relative activity and probability of occurrence, creating opportunities for reducing posterior uncertainty through the inclusion of meaningful covariates. Single‐species occupancy models with and without false‐positive detections removed were insufficient for determining local presence because of substantially biased occurrence and detection probabilities. We propose solutions to potential barriers for integrating local, short‐term and rangewide, long‐term acoustic surveys within a cohesive statistical framework that facilitates determining local species presence with uncertainty concurrent with estimating species–environment relationships.

Acoustic surveys of mixed fish aggregations often rely on manual allocation of acoustic energy to target species, with auxiliary information such as trawl catches and target strength distributions aiding interpretation. However, different teams of experts may use the same auxiliary data differently. In this experiment, seven teams of experts interpreted the same acoustic data, and we compared their classification to target categories to quantify uncertainty in the manual classification process. The teams largely agreed on the total acoustic energy attributable to organisms, but there was significant variation in how the teams split this energy on different target categories. This was caused by differences in applied thresholds for separating plankton and fish, as well as disagreements in species classification. For all target categories, the variation due to teams was lower than the overall variability across acoustic segments, but when scaled up to the number of segments in a typical survey, the team effect either dominated or was of similar magnitude as the segment variability. These results imply a need for further standardisation and uncertainty estimation of expert evaluations in acoustic surveys involving manual interpretation of echo sounder data. [ABSTRACT FROM AUTHOR]

An acoustic survey of Cuvier's beaked whales (Ziphius cavirostris) was conducted off the U.S. West Coast in August and September 2016 using drifting recorder systems with a vertical array of two hydrophones at a depth of ~110 m. Recorders were deployed 22 times to representatively cover a 1,058,000 km2 study area from the shelf break to ~556 km offshore. Vertical angles to echolocation pulses were measured using the signal time‐difference‐of‐arrival on the two hydrophones. Echolocation pulses of Cuvier's beaked whales were identified from their arrival angles (always from below the array) and unique acoustic characteristics. The density and abundance of Cuvier's beaked whales were estimated using a group‐based point‐transect analysis with 2 min time snapshots. The area effectively surveyed was estimated using a maximum simulated likelihood approach to fit the observed distribution of signal arrival angles. The acoustic availability of whales during their dive cycle was estimated from the duration of acoustic encounters using a mark‐recapture approach. Overall, Cuvier's beaked whales were present during 0.60% of snapshots, and their estimated average density is 5.12 animals per 1,000 km2 (CV = 0.27). Their estimated abundance in the study area is 5,454 individuals (95% credibility intervals: 3,151 to 8,907). [ABSTRACT FROM AUTHOR]

Advances in operational simplicity and cost efficiency have promoted the rapid integration of unoccupied aerial vehicles (UAVs) into ecological research, yet UAVs often disturb wildlife, potentially biasing measurements. Studies of UAV effects on wildlife to date have focused on UAV trajectory or distance; however, UAV size and noise could be critical variables influencing wildlife responses.Bats are cryptic aerial species that are difficult to survey using conventional means, and so we tested the effectiveness of drone‐based acoustic surveys for bats. We recorded the number of acoustic bat detections with and without a UAV present. We used three small, commercial rotary UAVs varying in size and noise intensity (249, 907, 1,380 g).Larger and louder UAVs deterred significantly more bats, with no effect of take‐off distance on bat activity. The smallest and quietest UAV model had a similar change in bat activity compared with control measurements. Drone noise increased with drone size, but all drones emitted in a similar range of frequencies that overlapped with the larger bat species that were also those most impacted by the UAV. During the 5‐minute surveys, there was no evidence of bat habituation to UAVs although bats returned quickly once the UAV survey ended.We urge wildlife researchers to consider drone size during wildlife surveys. Smaller and quieter models have negligible impacts on wildlife, eliminating the impact of drones on wildlife in some cases. [ABSTRACT FROM AUTHOR]

Aim: By virtue of their spatial extent, landscape‐scale monitoring programmes may be well‐suited to support before‐after/control‐impact (BACI) studies of major disturbances such as megafires, but they may only have a few affected sites, reducing statistical power. I tested whether a variety of hypothetical but logistically plausible survey designs could provide statistically powerful assessments of hypothetical but empirically based population responses to megafire. Location: Simulation focused on fire‐prone forests. Methods: I varied the number of affected sites, detection probability, baseline occupancy and species' responses to fire to create 72 monitoring scenarios. I then simulated 10 years of site occupancy data in which a megafire or other disturbance occurred between years 5 and 6 (n = 500 iterations). Results: Statistical power to correctly reject the null hypothesis of no population response to megafire was high (mean across all scenarios = 0.78), but power to identify the correct population response (e.g. post‐fire occupancy declined and then recovered) was low (mean = 0.29). Statistical power to not underestimate the effect of a megafire on site occupancy was fairly high (mean = 0.66), but power to accurately estimate site occupancy was low (mean = 0.25). Statistical power increased with the number of affected sites (i.e., sample size) and with the intensity of the focal species' response to megafire. Case study simulations based on an existing acoustic monitoring programme in the Sierra Nevada, USA, indicate that it is likely to identify Spotted Owl and Black‐backed Woodpecker population responses to megafires. Researchers can use the included simulation tutorial to implement their own power analyses. Main conclusions: Landscape‐scale monitoring programmes can identify population changes following megafires, but cannot reliably produce nuanced results, especially with only five years of post‐fire data. Smaller‐bodied species, which could be studied at more sites, are likely to be better focal species for megafire BACI studies. Aggregating landscape‐scale studies' sampling coverage across many fire footprints to study the overall effects of megafires—rather than the effects of individual fires—may be a more informative approach. [ABSTRACT FROM AUTHOR]

The acoustic survey is now gaining attention as a method by which to monitor birds. It has advantages over conventional methods, such as point count and line transect methods, because of its low disturbance to natural behaviors. Recent research has addressed development of automatic bird species identification systems using Artificial Intelligence (AI) techniques to actively identify bird calls. Despite a recent increase in research, an effective and systematic procedure has not been identified. To build an automated bird species identification process, we tested multiple methods of sound and image preprocessing with representative machine learning models. The target species was the Grey-faced Buzzard-eagle Butastur indicus, which is a species of raptor categorized as "Vulnerable (VU)" in the Japanese Red List. The sound files included the species' calls recorded at two different sites. The optimal sound threshold to detect the bird calls, and the sound duration to sample, were identified using a Convolutional Neural Network (CNN) model and evaluating the cross-validation and generalization performance. Alternative methods, including the random forest model and multi-layer perception model, were compared with the performance of CNN. We determined that the optimal method was applying CNN-based classification systems using sounds of 2-3 seconds, detected by the increase of 1-3 dB sound pressure level over the prior 10 milliseconds. The highest F1-score of cross-validation and generalization performance were 0.89 and 0.71, respectively. [ABSTRACT FROM AUTHOR]

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In 2016–2018, we carried out bat acoustic surveys in the northern part of the island of Cyprus and used two types of methods: stationary recordings (24 stations, 47:45 hours) and mobile acoustic driving transects (22 transects, 1,131 km, 54:20 hours). All bat acoustic records were attributed to habitat types obtained from CORINE Land Cover (CLC) data. We compared results from both methods and analysed seasonal and habitat associations with bat species that utilize the semi-arid Mediterranean landscape. Six selected bat species were associated with a total of 20 habitat types. The most frequent species, Pipistrellus kuhlii, was associated with almost all habitat types, with the highest flight activity in agricultural, urbanized and forested / seminatural habitats. Eptesicus serotinus and Hypsugo savii indicated preference of agricultural areas and avoidance of artificial surfaces. A χ2 test of independence revealed stronger habitat associations for stationary surveys, while habitat associations were weak for mobile transects. Given the vulnerability of Mediterranean landscapes, our study could be considered as a basis for establishing a long-term monitoring scheme with the goal of documenting predicted changes in bat communities as habitat is altered and as global temperatures rise. [ABSTRACT FROM AUTHOR]

In this study, the distribution of giant N. jellyfish by the echo counting method was investigated in the East China Sea, where giant N. jellyfish are known to breed and migrate to the coastal waters of Korea mainly in summer. In addition, the distribution densities by the survey method were compared with the sighting and trawl surveys. In the case of the East China Sea area and the Gijang coastal area, a split beam type scientific echosounder (EK60, Simrad, Norway) and Acoustic data at 38 and 120 kHz were collected while moving at 6–7 kts. In the coastal waters of Korea, acoustics data at 38 and 120 kHz were collected with a split beam type scientific echosounder (EK80, Simrad, Norway) attached to the bottom of the R/V Tamgu No. 21. In the East China Sea, the average distribution densities of acoustic, sighting, and trawl surveys were 8355.7 (10−6 ind/m3), 162.2 (10−6 ind/m3), and 792.5 (10−6 ind/m3), respectively. The average densities in the coastal waters of Korea of acoustic, sighting, and trawl surveys were 2238.7 (10−6 ind/m3), 664.9 (10−6 ind/m3), and 432.9 (10−6 ind/m3), respectively. The average distribution density of the acoustic survey conducted on 21 July 2020 in the coastal waters of Gijang was 1024.5 (10−6 ind/m3), and the sighting survey showed 48.8 (10−6 ind/m3). The sighting surveys conducted on 22 July 2020 were 393.3 (10−6 ind/m3) and 19.6 (10−6 ind/m3). The average distribution density for the acoustic survey performed on 23 July 2020 was 99.0 (10−6 ind/m3), and for the sighting survey was 197.2 (10−6 ind/m3). When comparing the results of the acoustic survey with the results of the sighting and the trawl surveys, all surveys except for the survey conducted on 23 July 2020 showed that the acoustic survey was higher than other survey methods.

The Atacama Myotis is an endangered and poorly studied bat species, endemic from Peru and Chile. Using mist nets and ultrasonic recordings we release new information on activity patterns and roost use by M. atacamensis in Chile. We also report new records for the species, extending its distribution range to Santiago Metropolitan region. Our results suggest a wide distribution and relative abundance of M. atacamensis in northern Chile, in addition to remarkable habitat diversity for populations of this species. Bats were active in both natural and anthropogenic habitats. Abandoned mines and buildings in rural villages were the roosts most used by the species. These data provide additional information on the distribution, ecology, and natural history of M. atacamensis and can be useful in the design of conservation action plans for populations in the country. [ABSTRACT FROM AUTHOR]

In this study, the identification of dominant fish species in the East Sea was conducted using the dB-difference method. The survey was conducted using the two frequencies of 38 and 120 kHz in transect 6 of the southern part of the East Sea. Information on fish species was identified using fishing gear and e-DNA, and the dominant target fish species were selected and analyzed as cod, anchovy, common squid, and herring. The dB-difference range for each fish species was set to −0.86 dB < ∆MVBS 38–120 kHz < 0.82 dB for cod and to the range of 2.66 dB < ∆MVBS 38–120 kHz < 2.84 dB for anchovy. The dB-difference of the common squid was set to −0.36 dB < ∆MVBS 38–120 kHz < 1.25 dB and to the range of 0.88 dB < ∆MVBS 38–120 kHz < 2.28 dB for herring; the fish species were then identified in the echograms. When comparing the results of swimming depths by fish species and previous studies, cod was detected mainly at the bottom of the sea, and anchovy and common squid were detected mainly at a depth of 50 m. Herring was detected to be mainly distributed in water depths from 50 to 150 m. [ABSTRACT FROM AUTHOR]

Context: Forest fire activity is expected to increase in many parts of the globe over the course of the 21st century, with corresponding potential for heightened levels of proximate and ultimate threats to avian diversity. Landscape-scale investigations of the responses of birds in locations where current extreme fire regimes represent those expected in the future provide opportunities to identify potentially vulnerable species in advance. Autonomous acoustic recorders are well suited to survey birds in the typically large and remote natural areas with low accessibility required for these types of studies, because they offer cost-effective and relatively safe options for obtaining reliable data. Aims: The present study aimed to optimise survey using acoustic recorders to achieve a satisfactory assessment of montane dry sclerophyll forest bird assemblages using these devices. Survey completeness, or the number of species detected as a percentage of total species, was used as a metric to gauge survey suitability. Methods: Acoustic recorders were deployed in 10 ridge-top forest sites in the Blue Mountains, south-eastern Australia. Extensive field recordings were processed by an analyst, with species detected by their calls recorded in a series of 20-min samples. A results-based approach, incorporating a stopping rule that established when to conclude sampling at a site, was applied to the data. The results guided the target survey completeness and sampling effort levels assigned to a set of fixed-effort survey methods, which were subsequently evaluated. Key results: The optimal survey method involved using recordings from five 20-min sampling periods immediately following dawn for 2 days, achieving an average survey completeness level of 69%. Conclusions: The optimal survey method can obtain results that are suitable for many types of studies involving assessments of bird assemblages, because the method can detect all common and moderately common species in assemblages, plus a fair proportion of rare species. Implications: The present study has systematically developed an effective method of using autonomous acoustic recorders to research and monitor montane bird assemblages in fire-prone dry sclerophyll forests. This methodological approach may also be applied in systems subject to altered patterns of flood, storm or other extreme weather under climate change. Changes to forest fire regimes under climate change will impact birds, so reliable and efficient methods of assessing and monitoring avian responses are required. This study aimed to optimise survey of bird assemblages using autonomous acoustic recorders, and found that using five 20-min post-dawn samples on each of 2 days was satisfactory for many types of studies. This method provides an effective option for surveying birds in montane dry sclerophyll forests. Photograph by M. Franklin. [ABSTRACT FROM AUTHOR]

Artificial reefs are often deployed by many countries for the purpose of enhancing fishing after a period of several years. The objective of this study was to analyze the effect of a pilot artificial reef system deployment in enhancing the demersal fish assemblages, investigated using both acoustic methods and bottom trammel nets, during four years between 2011 and 2017, in Xiangshan Bay, Zhejiang Province, China. Comparisons of community indices, including fish biomass, species richness and species diversity, indicated relatively consistent trends between the control sites and the artificial reefs following their deployment in 2012. Fish density, represented by the value of the nautical area scattering coefficient, and fish biomass were significantly higher on the artificial reefs than at the control sites in 2015 and 2017, and species richness and diversity were significantly greater at the reefs from 2013 to 2017. Blackhead seabream (Acanthopagrus schlegelii) and false kelpfish (Sebastiscus marmoratus) were the dominant fishes on the artificial reefs, and the average body lengths of these two species were significantly greater 40 and 64 months after deployment. Thus, construction of the artificial reefs appears to have achieved their primary purpose as fish‐attraction devices, thereby contributing to ecological restoration in Xiangshan Bay. [ABSTRACT FROM AUTHOR]

Conversion of natural land covers to agriculture is a major cause of the global biodiversity decline. Bats are an important component of biodiversity in agricultural landscapes because they provide pest control services. Although management recommendations towards the enhancement of insectivorous bat populations in agro-ecosystems have previously been highlighted, little information is available for promoting bat conservation within viticultural landscapes. In the present study, we examined the role of the adjacent habitat on bat activity in vineyards of central Chile. We also evaluated differences in bat activity between the edges and the interiors of the vineyards in relation to the type of adjacent habitat. To accomplish this, we conducted acoustic surveys along edge and the interior of 16 vineyards bordering different adjacent habitats. Overall bat activity in vineyards was not influenced by the adjacent habitat type, but it was by the location within the vineyard; edges showed significant higher activity than the interior of the vineyards. Vineyards adjacent to native vegetation showed the highest levels of activity for Lasiurus varius, Lasiurus villosissimus and Myotis chiloensis compared to those adjacent to monoculture or urban areas. All bat species were most active at the edges of the vineyards as compared to the interior, which increase the probability of this group providing ecosystem services in vineyards. Therefore, vineyard edges, in particular those adjacent to native vegetation, should be considered as part of agricultural management in order to promote bat diversity and abundance in this crop. [ABSTRACT FROM AUTHOR]

The density of ice krill (Euphausia crystallorophias), a species of key ecological value, and related environmental factors were observed along two transects in the Amundsen Sea Coastal Polynya (ASCP) in Antarctica. The distribution of ice krill was processed using two-frequency acoustic backscatter data identification, and the target strength of ice krill was calculated via stochastic distorted-wave born approximation based on the ice krill sample. The ice krill density ranged from 0.96 to 11.01 g m−2 for each transect (mean value was 5.77 g m−2 for the entire survey). These results were of a lower order of magnitude than those of a previous study in the same waters, although the ice krill was still the dominant krill specie in this polynya. We contend that the extent of the phytoplankton bloom might be the factor behind this difference, while other hydrographic parameters such as surface temperature and salinity would have some effect on the spatial distribution of ice krill abundance. Meanwhile, the density and height of ice krill abundance suggested that the diurnal effect on the ice krill was almost negligible. According to the fitted results of regression model, the abundance of ice krill in ASCP in 2022 summer was estimated approximately 175,000 tons. • Ice krill density and related factors were observed in the Amundsen Polynya, Antarctica. • The ice krill density ranged from 0.96 to 11.01 g m−2 in two sampled transects. • Ice krill was still the dominant krill species considering previous findings. • The ice krill density, however, distinctly declined compared to the density in 2012. • The phenomenon of ice melting and eutrophication possibly influenced the density. [ABSTRACT FROM AUTHOR]

The Cheer Pheasant (Catreus wallichii) is a protected species found abundantly to the west of Kaligandaki River. This study was conducted in the Myagdi district located in the western part of Kaligandaki River from October 2016 to June 2017. Our aim was to assess the habitat and population status of Cheer Pheasant, using acoustic survey and quadrate methods. A total of 38 breeding individuals were estimated in 7 bird/km2 density. The study also revealed that Cheer Pheasants showed a preference for exposure components of the habitat. They preferred moderately steep eastern slopes (10–35°) and steep southern slopes (35–67°) between 1800–2400 m elevations. Additionally low tree density and high herbs density showed a significant effect on the habitat choice of the species. Poaching and habitat destruction are the major threats in the study site, calling upon a strategic management plan for the long-term conservation of the Cheer Pheasant. [ABSTRACT FROM AUTHOR]

Bats are a highly diverse order with substantial economic and ecological value. Similarly, forests in South Africa form a valuable biome supporting unique biotic diversity, yet forest bat communities have not previously been surveyed. We sampled 17 forests, of seven forest types and three forest groups, in the Eastern Cape and southern KwaZulu-Natal provinces, located within the Maputaland-Pondoland-Albany global biodiversity hotspot. We utilized capture and acoustic survey methods to compile the first bat species inventory for these forests. Species identification was performed with a combined approach of morphology, echolocation, and DNA barcodes. With this we contributed novel DNA barcodes to the Barcode of Life Data System. A total of 25 species was recorded, with range extensions southward into the Eastern Cape for six species, indicating the region to be more diverse than previously thought. Updated modelled distribution maps for these species are presented. We compiled the first reference call library of hand released bats for South African forest habitats, and the southeast region of the country. We compared species richness, diversity, and dissimilarity of the forest types and found that Scarp forests host the highest species richness and diversity. Patterns of species assemblage similarities between forest groups are attributed to forest biogeographical history and historical dispersal routes of forest fauna. A comprehensive survey, such as this, may assist in the compilation and implementation of forest conservation management plans and future monitoring programs. [ABSTRACT FROM AUTHOR]

Acoustic monitoring provides an effective and non-invasive means to survey many species such as bats, birds and frogs. However, the acoustic monitoring poses challenges in determining the species identity due to lack of reference recordings or due to similar call structures across species. Here we recorded bats from 30 different locations at varying altitudes (0–1,200 m) and latitudes (7–12°N) using a full spectrum Pettersson M500-384 ultrasound detector. We used 2,070 pulses from 329 individual sequences of 20 bat species to standardise the echobank (catalogue of call characteristics). Discriminant function analyses (DFA) was carried out separately for the bats producing constant frequency (CF) and frequency modulated (FM) calls using frequency of maximum energy and end frequency, and shows an accuracy of 97.48% and 96.09% for CF and FM bats respectively. We also collated published reference calls for bat species in this region to develop a regional echobank for 42 species of echolocating bats from the Western Ghats. For six species, we report their echolocation calls for the first time. The echobank provides a useful tool for further conservation and monitoring studies in the wider region. [ABSTRACT FROM AUTHOR]

The geographic distribution of a species can provide insights into its population size, ecology, evolution, and how it responded to past (and may respond to future) environmental change. Improving our knowledge of the distribution of threatened species thus is a high priority in assessing their conservation status. However, there are few data available for many recently described yet understudied and potentially threatened primate taxa, making their conservation difficult. Here, we investigated the distribution of the Montagne d'Ambre fork-marked lemur, Phaner electromontis , a threatened nocturnal primate endemic to northern Madagascar and classified as Endangered by the IUCN. Because fork-marked lemurs are highly vocal, we used acoustic surveys to assess the species' presence-absence and relative population density within 66 distinct forest survey sites in northern Madagascar. Further, we compared data among five forest types within the study area and investigated the relationship between relative population density and climate variables. We report the presence of P. electromontis in 22 study sites; several of these populations were unknown previously. Although we found P. electromontis most frequently in dry-transitional forests, our results suggest that geography (spatial autocorrelation) rather than environmental variables explains the species' distribution. We hypothesize that environmental unpredictability and gummivory, combined with the presence of several distinct Phaner species in the studied area, could explain the observed distribution. [ABSTRACT FROM AUTHOR]

Evidence-based management of large carnivores is a crucial step towards their effective conservation. However, monitoring of these populations is demanding and generally requires substantial fieldwork effort. Lately, citizen science has become an increasingly important part of wildlife monitoring, but can that endanger studied species? In this paper, we describe our experiences with recruiting and involving volunteers in annual howling surveys of grey wolf (Canis lupus) population in Slovenia and present the framework about the use of citizens for collecting data. Huge effort of participants in a 7-year-long monitoring at a national scale has yielded a total of 116 wolf vocal responses, including 53 confirmed litters. Annually, between 5 and 12 reproductive packs were detected and an increasing trend in wolf population throughout the study period was observed. Volunteer-based howling surveys proved to be a cost-effective method for detection of reproductive packs on a large spatial scale, offering an insight into wolf population trends across a longer time period and we provide some recommendations for organisation and coordination of surveys. We also discuss ethical issues raised from our experience in using citizen science for this purpose. [ABSTRACT FROM AUTHOR]

Where large landscape modifications are planned, e.g. for infrastructure or exploitation, ecological impact assessments are required because of their potential effects on environment and species. Methods that make such assessments more standardized, efficient, and reliable are highly desirable. This paper proposes a new connectivity-based habitat model for bats (PREBAT), which could be used as a tool for impact assessments. Using data that was specifically collected for this purpose, the performance of PREBAT is critically analyzed and discussed. For this study, 50 sites within an area of 850 km2 in eastern Sweden were inventoried for four nights each using automatic ultrasound recorders to get an empiric measure of bat occurrence that could be compared with PREBAT predictions. The correlation between the predicted values from PREBAT and the observed bat activity (number of recordings) or species richness was tested using generalized linear mixed models. Predicted values of PREBAT are significantly correlated to the number of species that regularly (more than one night) occur at a given site, but not to the total number of species. PREBAT performed also much better at predicting the activity of forest-living species than overall bat activity, which makes PREBAT particularly suitable for predicting conflicts for those species. This study proposes a new habitat model for bats that takes spatial connectivity between habitat patches into account. PREBAT is shown to perform satisfyingly and has the potential to become a useful tool in assessing the ecological impact of large-scale landscape modifications. [ABSTRACT FROM AUTHOR]

Clean basal and capping argillaceous sandstone couplets in deep water settings have been previously interpreted as the result of spatially segregated turbidity currents and debris flows or spatio‐temporal transitioning of a turbulent flow to a transitional/laminar state. However, this paper presents three‐dimensional laboratory experiments demonstrating that a single sediment‐gravity flow can develop sand–mud couplets by autogenic remobilization of sediments that are still in the process of being deposited. This remobilization appears common to flows composed of mixtures of sand and mud with viscosities and strengths measurably greater than water, but not so high as to fully suppress the settling of sand through the depositional current. Dewatering in the early sand deposit acts to lubricate the basal portion of the increasingly muddy upper division of the flow, causing it to accelerate downslope, triggering a secondary flow with a sediment composition distinct from the original mixture. Sediment deposition and remobilization processes in a single sediment‐gravity flow and their resultant deposit were imaged acoustically and cored at representative locations within the deposit. The acoustic data and cores show sand–mud couplets that are qualitatively similar to interpreted turbidite–debrite‐like couplets in natural systems. [ABSTRACT FROM AUTHOR]

The bat survey in the Greek part of the Prespa basin in 2018-2020 confirmed, despite the limited methods used, its extraordinary importance for bat diversity. The study documented the presence of 22 bat forms (20 species) by acoustic surveys and a favourable status of some roosts including several nursery colonies. Three of the recorded species are here reported for the first time, Eptesicus nilssonii (the first record for Greece), Nyctalus lasiopterus, and Barbastella barbastellus, however, confirmation by a capture or direct observation of an individual is still needed. The collected data showed that bats do not avoid the urbanized parts of the study area and underlined the importance of old houses, churches, and ruins providing suitable roosting and foraging opportunities. The measurements of light pollution in villages revealed a high amount of light diffusion caused by the used type of shieldless luminaires. Heat maps of light intensity revealed a slightly higher bat activity in almost all villages in 2020, upon the situation in 2018. Bat passes were recorded not only in the peripheries of the highest illumination zones but also inside them, although some of the bat passes may belong to bats flying enough in the dark above the light levels of the installed lamps. The study provides application of mitigation actions for the Municipality of Prespa with the main aim to reduce the current level of the ALAN (Artificial Light At Night). [ABSTRACT FROM AUTHOR]

During several hours of acoustic survey of bats in Borgo Maggiore, San Marino, on 30 August 2020, foraging activity of at least six bat species was recorded. Five of them (Eptesicus serotinus, Hypsugo savii, Pipistrellus pipistrellus, P. kuhlii, and Tadarida teniotis) are common and widespread across the Apennine Peninsula and are already known members of the bat fauna of San Marino. The sixth species, Nyctalus noctula, is here reported from this country for the first time and the bat fauna of San Marino increases to 18 species. [ABSTRACT FROM AUTHOR]

Two Saildrone unmanned surface vehicles (USVs) were instrumented with echosounders and deployed in the Bering Sea to make acoustic observations of walleye pollock for 103 days. The Saildrones proved to be a suitable platform for measurement of fish backscatter: they produced high-quality measurements at wind speeds of <10 m s−1. Pollock backscatter measured from the Saildrones was compared to backscatter measured by a noise-reduced research vessel during two "follow-the-leader" comparisons. In a location where pollock were shallowly distributed (30–100 m), there was evidence of depth-dependent avoidance reactions to the ship. This behaviour was not evident in a second comparison, where the fish were primarily deeper than 90 m. Opportunistic comparisons indicate that backscatter where the ship and USVs crossed paths was similar. However, the Saildrones observed higher densities of shallow fish, which is consistent with the diving response inferred in the first follow-the-leader comparison. USVs equipped with echosounders, like all platforms, have inherent strengths (endurance) and limitations (species identification) that should be carefully considered for a given application. USVs can complement traditional ship-based surveys by increasing the spatial and temporal extent of acoustic observations, and their use is likely to become more widespread. [ABSTRACT FROM AUTHOR]

Pacific herring (Clupea pallasii Valenciennes, 1847) is a commercially important species that inhabits the coastal waters of the North Pacific from Korea to California, USA. This study analyzed the target strength (TS; dB re 1 m2) of Pacific herring individuals (n = 14, total length (LT) = 21.3–32.3 cm) at 38 and 120 kHz using ex-situ measurements and the Kirchhoff-ray mode (KRM) model. The least-squares regressions of the TS–LT relationship for the ex-situ measurements were TS38kHz = 20 log10(LT) − 70.10 (r = 0.17) and TS120kHz = 20 log10(LT) − 70.59 (r = 0.10). The least-squares regressions for the KRM model were TS38kHz = 20 log10(LT) − 68.39 (r = 0.40) and TS120kHz = 20 log10(LT) − 69.74 (r = 0.49). The b20 value of the KRM model was 1.71 dB higher than that of the ex-situ measurement at 38 kHz but similar at 120 kHz. These results provide basic data to evaluate the distribution and abundance of Pacific herring using fisheries’ acoustic technology.

In this study, the identification of dominant fish species in the East Sea was conducted using the dB-difference method. The survey was conducted using the two frequencies of 38 and 120 kHz in transect 6 of the southern part of the East Sea. Information on fish species was identified using fishing gear and e-DNA, and the dominant target fish species were selected and analyzed as cod, anchovy, common squid, and herring. The dB-difference range for each fish species was set to −0.86 dB < ∆MVBS 38–120 kHz < 0.82 dB for cod and to the range of 2.66 dB < ∆MVBS 38–120 kHz < 2.84 dB for anchovy. The dB-difference of the common squid was set to −0.36 dB < ∆MVBS 38–120 kHz < 1.25 dB and to the range of 0.88 dB < ∆MVBS 38–120 kHz < 2.28 dB for herring; the fish species were then identified in the echograms. When comparing the results of swimming depths by fish species and previous studies, cod was detected mainly at the bottom of the sea, and anchovy and common squid were detected mainly at a depth of 50 m. Herring was detected to be mainly distributed in water depths from 50 to 150 m.