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Side-scan sonar images of Antillean manatees. All images are from the wetlands of Tabasco, Mexico. Figure symbols: manatee (M), shadow produced by manatee (S). A1) Screen capture of left side of sonar image of an adult manatee directly below the boat swimming down towards the bottom. A2) Digitally-enhanced interpretation of A1 highlighting the acoustic response of the manatee body (red) and the shadow produced (gray). B1) Screen capture of left side of sonar image of three adult manatees. B2) Digitally-enhanced interpretation of B1 highlighting the acoustic response of the manatee bodies (red) and the shadows produced (gray). C1-C6) Screen captures from left side of sonar image of a mother-calf pair, except C6 which includes an additional adult manatee, with the side-scan sonar range between 15-60 ft (4.6-18.3 m). Images for C1-C6 have been cropped along the axis of boat travel and rotated counterclockwise 90 degrees to highlight how the manatee acoustic image and the proportion of the water column and bottom response change with increasing side-scan sonar range.
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Manatees are tropical marine mammals that live in a wide variety of aquatic habitats ranging from coastal marine areas to freshwater lakes and rivers located hundreds of kilometers inland. All manatee species are currently characterized as Vulnerable by the International Union for Conservation of Nature (IUCN), primarily due to anthropogenic causes...
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Abstract: Manatees are tropical marine mammals that live in a wide variety of aquatic habitats ranging from coastal marine areas to freshwater lakes and rivers located hundreds of kilometers inland. All manatee species are currently characterized as Vulnerable by the International Union for Conservation of Nature (IUCN), primarily due to anthropoge...
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... Abundance estimation using acoustics appears as a promising alternative, since it is not necessary to visualize the animals, but rather to detect sounds and/or images produced by ensonified manatees. The use of side scan sonar has proven to be a useful tool to detect manatees in such environments (Gonzalez-Socoloske et al., 2009;Gonzalez-Socoloske & Olivera-Gómez, 2012Arévalo-González, et al., 2014;Brice, 2014;Castelblanco-Martínez & Arévalo-González, 2015;Guzman & Condit, 2017;Serrano et al., 2017), and as the detection rates in the wild varied from 81 to 93% in clear and turbid waters, Gonzalez-Socoloske et al. (2009) concluded that side-scan sonars are sensitive enough to accurately detect the presence of manatees in their natural environment and can be an effective and accessible tool to study the species throughout its distribution. ...
The West Indian manatee is one of the most threatened speciesin Brazil. The species has currently a patchy distribution from thestate of Alagoas to the state of Amapá. The difficulty of observingmanatees, especially in estuarine waters, is a challenge forconservation. Therefore, it is necessary to use new methodologiesand technologies to solve manatee detection problems in theirnatural habitats. The goal of this study was to use an activeacoustic method of detection to estimate manatee density andabundance in the estuarine complex of the Timonha and Ubatuba rivers, between the states of Ceará and Piauí, northeast Brazil. Data collection was conducted from a wooden boat with an outboard motor using a side-scan sonar. Sonar images were collected along line transects in three regions within the study area. Manatee abundance was calculated using distance sampling (Distance 6.0 software). There were 1,396 transection lines that totaled 863.6 km traveled in the study area. The observed general encounter rate was 0.089 group detected per kilometer traveled. The best detection model was the hazard-rate with no adjustment terms, resulting in a detection probability of 33.7%, and an estimated density for the entire study area of 9.19 manatees per km 2. Abundance of manatees in the estuary was estimated to be 37 animals (CV% = 30.2, 95% CI = 21-66). The methodology using side-scan sonar proposed here was successful in the detection of manatees in the study area and in defining parameters for its use to estimate the population size using the distance sampling method. This study provides an estimate of manatee density and abundance in a key estuarine system along the northeast coast of Brazil, which can serve as a baseline for future studies and aid in the development of conservation strategies for the species. This is the first time this methodological approach has been used for manatee detection and abundance estimation in Brazil. We recommend the use of side-scan sonar in future West Indian manatee research.
... Recreational-grade side-scan sonar (SSS) units have made this technology more accessible due to its low cost and the availability of third-party software to translate SSS imagery (e.g., Litts, 2008, 2010). Recreational-grade SSS has increasingly been used to image a number of large, aquatic animals such as West Indian manatees Trichechus manatus (Gonzalez-Socoloske et al., 2009;Gonzalez-Socoloske and Olivera-Gomez, 2012), sturgeon Acipenseridae Hightower, 2013, 2015;Andrews et al., 2020), Alligator Gar Atractosteus spatula (Fleming et al., 2018), and Paddlefish Polyodon spathula (Wolfenkoehler et al., 2023). Wolfenkoehler et al. (2023) detected Paddlefish on SSS up to 25 m away, allowing the use of distance sampling methods to estimate abundance, but detection by distance exhibited strong exponential declines. ...
Recreational-grade side-scan sonar (SSS) has only recently been applied to estimate abundance of Paddlefish Polyodon spathula, a large pelagic planktivore, in reservoirs. Current recreational-grade SSS units also have a dedicated down-scan channel, which may be useful for detecting Paddlefish in reservoirs because the range of depths they inhabit. We investigated the utility of down-scan images using SSS data from a previously published study of Paddlefish in Keystone Lake, Oklahoma. Two readers counted Paddlefish and estimated the depth of each fish and the water column. We used proximity functions in a geographic information system to find individual Paddlefish that were common between the readers. We further used proximity functions to identify common fish observed from the SSS survey conducted previously as an aid to compare and refine down-scan estimates. Depth of Paddlefish averaged approximately 7 m, but fish were deeper when water was deeper. Density estimates from down-scan were comparable to side-scan, but only after utilizing the side-scan data to adjust for detection-by-distance in a dual-gear approach. Down-scan data thus appear to be useful for not only estimating density of Paddlefish, but also for incorporating depth use, creating a three-dimensional database of locations that can inform managers of optimal depths for sampling gear (e.g., gill nets), improve monitoring efficiency, and facilitate better management of reservoir populations.
... Radio-tagged Antillean manatees in Mexico sometimes migrated over 100 km from Chetumal Bay, Mexico to Belize 34 while most of the individuals tagged in Belize remained within 25 km of where they were captured 35 . In Panama, a lone female was tagged in the San San Pond Sak region and remained in this region throughout the study 36 . The authors cautiously suggest that the San San Pond Sak system contains habitat suitable to high site fidelity in manatees. ...
Geographic variation in the vocal behavior of manatees has been reported but is largely unexplored. Vocalizations of wild West Indian manatees (Trichechus manatus) were recorded with hydrophones in Florida from Florida manatees (Trichechus manatus latirostris), and in Belize and Panama from Antillean manatees (Trichechus manatus manatus) to determine if calls varied between subspecies and geographic regions. Calls were visually classified into five categories: squeaks, high squeaks, squeals, squeak-squeals, and chirps. From these five categories, only three call types (squeaks, high squeaks and squeals) were observed in all three populations. Six parameters from the temporal and frequency domains were measured from the fundamental frequency of 2878 manatee vocalizations. A repeated measures PERMANOVA found significant differences for squeaks and high squeaks between each geographic location and for squeals between Belize and Florida. Almost all measured frequency and temporal parameters of manatee vocalizations differed between and within subspecies. Variables that may have influenced the variation observed may be related to sex, body size, habitat and/or other factors. Our findings provide critical information of manatee calls for wildlife monitoring and highlight the need for further study of the vocal behavior of manatees throughout their range.
... The use of Side Scan Imaging Sonar beams (SSI) has been explored to detect and count manatees on turbid or dark waters with promising results (González-Socoloske et al. 2009;González-Socoloske and Olivera-Gómez 2012;Arévalo-González et al. 2014;Puc-Carrasco et al. 2016Guzmán and Condit 2017;Castelblanco-Martínez et al. 2017). This sonar has also been used to detect other aquatic fauna (Davy and Fenton 2013;Flowers and Hightower 2013). ...
Manatees are threatened along their range. In México, this species is listed as endangered. Manatee conservation strategies require density or occupancy estimates, especially in areas where species face survival risks. On turbid waters, like those found in rivers and lakes of the Southern Gulf of México coast, visual methods used to detect and count manatees underestimate actual numbers. Our goal was to estimate the density and abundance (N) of Antillean manatees in a small State Natural Protected Area, where a manatee population of unknown size inhabits. We performed line transects using a side scan sonar to detect animals and mark-recapture in the isolated population of manatees within Laguna de las Ilusiones, México, a landlocked lake that excludes transit. Using distance sampling from 14 boat trips, estimates of density and abundance were 15.5 manatees km-2 and 27 ± 5 manatees in the lake (CV ≈ 16.6 %). With MARK, from six capture events and 19 individual encounter records, the abundance estimated was 24 manatees (CV ≈ 16 to 24 %). Previous number of manatees were based only on visual surveys, which reported at least seven manatees. Density is lower than other similar studies along narrow waterways in important areas in México and other Central and South America countries. Studying this endangered subspecies is limited by cryptic habits, turbid waters, poor funding, and low densities, making density or abundance estimates difficult. However, within particular areas and established monitoring areas, these methods could be useful to generate baselines for conservation strategies.
... (Gonzalez-Socoloske et al., 2009). However, it was surprising to see the number of unique locations (at least seven, including Catazajá wetlands in Chiapas, Alvarado Lagoon System in Veracruz, Laguna de las llusiones, Pantanos de Centla, and San Pedro River in Tabasco, Laguna de Terminos in Campeche, and Rio Hondo in Quintana Roo) and independent research groups (at least seven) within Mexico that are using the methodology(Rodas-Trejo et al., 2008;Gonzalez-Socoloske et al., 2009;Daniel- Rentería et al., 2012;Gonzalez-Socoloske & Olivera-Gomez, 2012;Acevedo-Olvera et al., 2015;Puc-Carrasco et al., 2016;Puc-Carrasco et al., 2017;Ramírez-Jiménez et al., 2017;Serrano et al., 2017;Ladrón de Guevara-Porras et al., 2019;Corona-Figueroa et al., 2021, 2022. ...
Manatees are aquatic mammals that live in a variety of environments. Many of those shallow water environments have murky water, making detection using traditional visual surveys very challenging. Side-scan sonar was first proposed as a tool to detect and study manatees in these complicated habitats in 2005. Here, we summarize the use of this tool from 2005 to 2022 by searching the available literature. Our literature search revealed that this tool is being widely used in more than 20 locations and
over 15 countries. All three manatee species are being studied with side-scan sonar. It is most useful in murky freshwater habitats that are not too deep or open (e.g., large lagoons or lakes), where visual surveys are not effective. Most studies used side-scan sonar in combination with other methodologies such as passive acoustics and indirect evidence. Work is still needed to standardize the use of this technique so that image interpretation can be reliable, and results can be compared between studies. However, most studies indicated that this tool is essential in murky water habitats and provides one of the best ways to detect and study manatees.
... These studies represent important baseline information for monitoring and management and are often based on simple methods to collect manatee information such as interviews of local inhabitants, detection of indirect signs of presence (feeding signs, feces), or fixed-point visual surveys from shore or floating platforms. Nevertheless, during the last decade, there has been an important increase of documents describing the utilization of more sophisticated monitoring tools, such as telemetry (e.g., Castelblanco-Martínez et al., 2013;Gonzalez-Socoloske et al., 2015;Normande et al., 2016;Attademo et al., 2022;dos Santos et al., 2022), side-scan sonars (e.g., Gonzalez-Socoloske et al., 2009;Gonzalez-Socoloske & Olivera-Gómez, 2012;Arévalo-González et al., 2014;Guzman & Condit, 2017;Castelblanco-Martínez et al., 2018;McLarty et al., 2020;Corona-Figueroa et al., 2021), drones (e.g., Ramos et al., 2018Ramos et al., , 2022Landeo-Yauri et al., 2020, and hydrophones (e.g., Kikuchi et al., 2014;Rivera-Chavarría et al., 2015;Merchan et al., 2019). Likely, in the upcoming years, the rapid evolution of detection and tracking devices -and the increase in their affordability -will have a positive impact on the amount and quality of data about Antillean manatee presence, movements, and habitat use in developing countries. ...
conducted on wild manatees, 21,5% under human care conditions, and the rest a combination of both; the most common topics of study were 'ecology', 'conservation', 'morphology, anatomy and physiology', and 'behavior'. The literature on Antillean manatee has expanded significantly over the last two decades across the region, with most of the research published in just the last five (25.4%) to 10 (44.6%) years. Most of the published work has been by Brazilian, Mexican, and Colombian researchers. However, an important amount of research remains as theses in Portuguese or Spanish limiting the dissemination of results. Relevant limitations for research and publication in Latin American countries may have an impact on the published literature on Antillean manatees, including scarce funding, poor facilities, language-related difficulties, and lack of a culture of publication. Avenues to melt scientific barriers may include increasing governmental investment on research, strengthening international networks, and improving the support to publish in high-impact journals.
... Many studies have established sound navigation and ranging (SONAR) scans as a valuable method of underwater detection of Antillean manatees (T. m. manatus) in their turbid waters of Mexico and Central America, with manatee detection frequencies of up to 93% (Gonzalez-Socoloske et al., 2009;Gonzalez-Socoloske and Olivera-Gomez, 2012;Guzman and Condit, 2017;Puc-Carrasco et al., 2017;Castelblanco-Martıńez et al., 2018). In addition, manatees produce a variety of vocalizations including squeaks, screeches, whines, and trills (Umeed et al., 2018;Brady et al., 2020;Baotic et al., 2022) shown to be important for their underwater communication and emitted across various behavioral states (Bengtson and Fitzgerald, 1985;O'Shea and Poche, 2006;Brady et al., 2021). ...
... (LaCommare et al., 2008;Gonzalez-Socoloske et al., 2009;Gonzalez-Socoloske and Olivera-Gomez, 2012;Kikuchi et al., 2013;Rivera Chavarria et al., 2015;Guzman and Condit, 2017;Puc-Carrasco et al., 2017;Castelblanco-Martıńez et al., 2018;Rycyk et al., 2021;Rycyk et al., 2022). ...
The African manatee (Trichechus senegalensis) is an elusive, data-deficient, and endangered species which inhabits marine and freshwater systems throughout Western and Central Africa. A major challenge in understanding the species ecology and distribution is the difficulty in detecting it using traditional visual surveys. The recent invasion of Giant Salvinia (Salvinia molesta) at the most important site for the species in Cameroon further limits their detectability and may restrict their movements and habitat use. To investigate methods’ effectiveness in detecting African manatees, we conducted monthly vessel surveys from which visual point scans, 360° sonar scans, and passive acoustic monitoring were conducted simultaneously at ten locations and over 12 months in Lake Ossa, Cameroon. Manatee detection frequency was calculated for each method and the influence of some environmental conditions on the methods’ effectiveness and manatee detection likelihood was assessed by fitting a binary logistic regression to our data. Detection frequencies were significantly different between methods (p < 0.01) with passive acoustics being the most successful (24.17%; n = 120), followed by the 360° sonar scan (11.67%; n = 120), and the visual point scan (3.33%; n = 120). The likelihood of detecting manatees in Lake Ossa was significantly influenced by water depth (p = 0.02) and transparency (p < 0.01). It was more likely to detect manatees in shallower water depths and higher water transparency. Passive acoustic detections were more effective in uninvaded areas of the Lake. We recommend using passive acoustics to enhance African manatee detections in future surveys.
... The need to overcome these limitations and improve our knowledge about the role of aquatic mammals in marine and freshwater ecosystems, and how human activities are affecting the natural balance, has promoted the development of new research disciplines and enhanced the use of new technologies in the field (e.g. Block et al., 2011;Gonzalez-Socoloske and Olivera-Gomez, 2012;McIntyre, 2014;Nowacek et al., 2016;Hastie et al., 2019). Some may have mostly negligible impact, such as the use of unmanned aerial vehicles (UAVs) and underwater photography to study cetaceans Nowacek et al., ...
... Side-scan sonar surveys have been used extensively to study river systems to estimate the abundance of large fish (Flowers & Hightower, 2013) and mammalian species (Gonzalez-Socoloske & Olivera-Gomez, 2012), identify specific habitat types (Graham, Hafs, & Kennedy, 2017;Kaeser & Litts, 2008), classify large areas of substrate (Anima, Wong, Hogg, & Galanis, 2007;Kaeser et al., 2013), and assess habitat partitioning (Goclowski, Kaeser, & Sammons, 2013). In this study, we used side-scan sonar substrate data to address two questions: how does the ability of substrate to explain differences in fish distribution within rivers vary among species?; and, how does the scale at which substrate is assessed affect its explanatory power for a given species? ...
Physical habitat is crucial for structuring local fish assemblages. Understanding habitat structure is important for fish management and conservation. Herein, we assessed whether sonar‐derived substrate data could explain spatial variation in species‐catch rates. Using a side‐scan sonar, we mapped the substrates of two non‐wadeable rivers in Illinois, USA and conducted standardized fish surveys at 40 sites over a 3‐year period. We used four fish species from lentic and lotic guilds, with each guild represented by a large piscivore and small insectivore. For each of the 40 sites, we characterized substrate composition at five spatial scales (0.1, 0.5, 1, 2, and 5 km) and used linear regression to explain site variations in species abundance or biomass. We hypothesized that larger spatial scales would better explain the catch rates of large species, and that biomass would be better explained than abundance. The proportion of variance in fish‐catch rates, explained by substrate composition, varied greatly (0.02 ≤ adjR2 ≤ 0.74, mean adjR2 = 0.38) with respect to species, spatial scales, and predictors used. However, we did not observe a consistent relationship between body size and the most relevant scale. Species biomass was more closely related to substrate composition than was species abundance and the best models selected based on AICc reached an average adjR2 of 0.49 (0.25–0.74) across the four species, compared with that of 0.43 (0.20–0.64) obtained via the best abundance‐based models. We conclude that substrate data obtained using side‐scan sonar are useful for improving our understanding of river fish ecology.
... Active sonar has been used extensively in studies of marine mammal behaviour underwater (e.g. Benoit-Bird & Au, 2003a;Doksaeter, Godo, Olsen, Nottestad, & Patel, 2009;Gonzalez-Socoloske & Olivera-Gomez, 2012;Nøttestad, Ferno, & Axelsen, 2002;Pyć, Geoffrey, & Knudsen, 2016) to track the movements of individual animals in a range of different habitats. Hawaii. ...
... Hawaii. Furthermore, West Indian manatee (Trichechus manatus) behaviour was measured in waters with very poor visibility (due to turbidity and sediment load) using a range of side-scan sonar systems (Gonzalez-Socoloske, Olievera-Gomez, & Ford, 2009;Gonzalez-Socoloske & Olivera-Gomez, 2012), and bottlenose dolphin (Tursiops truncatus) movements were tracked in high tidal flows using a 455 kHz Reson Seabat 6012 (Ridoux et al., 1997). ...
Many marine industries may pose acute risks to marine wildlife. For example, tidal turbines have the potential to injure or kill marine mammals through collisions with turbine blades. However, the quantification of collision risk is currently limited by a lack of suitable technologies to collect long‐term data on marine mammal behaviour around tidal turbines.
Sonar provides a potential means of tracking marine mammals around tidal turbines. However, its effectiveness for long‐term data collection is hindered by the large data volumes and the need for manual validation of detections. Therefore, the aim here was to develop and test automated classification algorithms for marine mammals in sonar data.
Data on the movements of harbour seals were collected in a tidally energetic environment using a high‐frequency multibeam sonar on a custom designed seabed‐mounted platform. The study area was monitored by observers to provide visual validation of seals and other targets detected by the sonar.
Sixty‐five confirmed seals and 96 other targets were detected by the sonar. Movement and shape parameters associated with each target were extracted and used to develop a series of classification algorithms. Kernel support vector machines were used to classify targets (seal vs. nonseal) and cross‐validation analyses were carried out to quantify classifier efficiency.
The best‐fit kernel support vector machine correctly classified all the confirmed seals but misclassified a small percentage of non‐seal targets (~8%) as seals. Shape and non‐spectral movement parameters were considered to be the most important in achieving successful classification.
Results indicate that sonar is an effective method for detecting and tracking seals in tidal environments, and the automated classification approach developed here provides a key tool that could be applied to collecting long‐term behavioural data around anthropogenic activities such as tidal turbines.
