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Photo of male spotted eagle ray Aetobatus narinari swimming with Lotek acoustic transmitter. Acoustic transmitters were externally secured to the dorsal “saddle” region, allowing for normal oscillatory swimming motion. White arrow points to transmitter location.
Source publication
Declines of large sharks and subsequent release of elasmobranch mesopredators (smaller sharks and rays) may pose problems for marine fisheries management as some mesopredators consume exploitable shellfish species. The spotted eagle ray (Aetobatus narinari) is the most abundant inshore elasmobranch in subtropical Bermuda, but its predatory role rem...
Citations
... Research on elasmobranchs (i.e., sharks and batoids) in Bermuda has been modest, with a few studies of the sixgill shark (Hexanchus griseus) (4,5), satellite tracking of the tiger shark (Galeocerdo cuvier) (6,7), and the only research on batoids coming from a single species, the whitespotted eagle ray (Aetobatus narinari) (8)(9)(10)(11). The whitespotted eagle ray has long been considered the sole inshore ray species in Bermuda (12); however, reports of large dasyatid rays (e.g., Bathytosia centroura) are emerging [(13); iNaturalist]. ...
... Visual surveys were conducted by scientists in October 2022, July 2023, and October 2023. Surveys followed the methods of Ajemian et al. (8), targeting whitespotted eagle rays. Briefly, 2-3 individuals stood at the bow of the vessel while navigating across Harrington Sound and Flatts Inlet at slow speeds (<4 kt). ...
... While Bermuda is (at its closest) 960 km from Cape Hatteras, North Carolina, and thus within the migration distances (<1,000 km) recorded for cownose rays along the continental U.S. (27,28), movements over deep ocean basins (i.e., off the continental shelf) appear uncommon [max recorded depth ∼50 m (27)]. Though capable of extensive migrations (100's of km) in the Gulf of Mexico (29), the native and related pelagic ray species A. narinari does not appear to leave Bermuda waters seasonally (8,9), although movements into deeper waters are likely in the winter (11). The tiger shark, on the other hand, regularly migrates between Bermuda, Bahamas, and the Turks and Caicos Islands (6), Lemon (Negaprion brevirostris) and blacktip (Carcharhinus limbatus) sharks are capable of similar migrations over deep waters and have also been recorded to connect waters of the U.S. Virgin Islands and Florida Atlantic coast (30). ...
Cownose rays (Family Rhinopteridae) are highly migratory pelagic rays that are generally restricted to continental shelves. Despite 100's of years of natural history records, cownose rays have never been reported in Bermuda, an atoll-like coral reef ecosystem that is separated from the continental mainland United States by ~1,000 km. Here we compile evidence that the Atlantic cownose ray ( Rhinoptera bonasus ) has recently established in Bermuda, supported by both morphological and genetic data. Potential ecological and inter-specific competition concerns are presented as well as probable physical mechanisms that facilitated this recent and presumed range expansion.
... Un conjunto de especies que conforman a los mesopredadores en estos sistemas son las rayas (superorden Batoidea), las cuales, también se caracterizan por interacciones no tróficas, ya que durante actividades de forrajeo o descanso, excavan y perturban los sedimentos, influyendo en la estructura a las comunidades circundantes infaunales (especies que habitan por debajo de la superficie del sedimento marino) y afectando los ciclos biogeoquímicos en los ecosistemas marinos a pequeña escala (Flowers et al., 2021). Además, su capacidad para influir en la composición de la comunidad y la abundancia relativa de especies presa es afectada por el uso, el movimiento y los patrones de distribución del hábitat (Ajemian et al., 2012). ...
... La raya águila de puntos blancos Aetobatus narinari, es la especie más conocida entre los aetobátidos. A estos se les clasifica como durófagos, debido a que consumen presas que poseen concha, predominando en su dieta los moluscos y crustáceos (Ajemian et al., 2012;Serrano-Flores et al., 2018). Son de crecimiento lento, madurez sexual tardía (de los dos a seis años), baja fecundidad (en promedio tres crías por parto) y largos periodos de gestación (12 meses) (Tagliafico et al., 2012;Boggio-Pasqua et al., 2022). ...
... Asimismo, en el Golfo de México y el Caribe se ha identificado en A. narinari un patrón de estancia y retorno a determinados sitios (Ajemian y Powers, 2014;Bassos-Hull et al., 2014;Cerutti-Pereyra et al., 2017;Degroot et al., 2021), así como avistamientos de agregaciones de hasta más de 50 individuos (Bassos-Hull et al., 2014), algunos de estos sitios se han asociado con la presencia de sus presas principales (Ajemian et al., 2012;Serrano-Flores et al., 2018). ...
... Later, studies of the whitespotted eagle ray diet from the greater Caribbean region suggested diets consisting of conch species, including queen (Strombus gigas) and rooster conch (Strombus gallus [10,11]), which similarly were devoid of shell and identifiable opercula. Gut contents of whitespotted eagle rays sampled in Bermuda consisted primarily of bivalves, including calico clams (Macrocallista maculata), lucinid clams (Codakia sp.), eared arks (Anadara notabilis) and purplish tagelus (Tagelus divisus), along with a few gastropods such as milk conch (Strombus costatus [12]). Conversely, whitespotted eagle ray diets analyzed in Mexico consisted primarily of gastropods, including the West Indian fighting conch (Strombus pugilis), netted olive snail (Americoliva reticularis) and milk conch (Lobatus costatus), in addition to the giant red hermit crab (Petrochirus diogenes) for large females [13]. ...
... Additionally, the diet for individuals caught in Australia also included crustaceans [14]. In most aforementioned cases (excepting [12]), rays were sacrificed, and the entire digestive tract was assessed; however, all previous cases used visual identification to describe the diet. ...
... While we did encounter strombid conchs in the lavage contents here (L. raninus and S. alatus) and in Bermuda (Strombus costatus [12]), the tissues of these animals are considerably larger and tougher than those of the bivalves consumed, and thus may not have been fully dislodged from the gastrointestinal tract of the rays during the lavage process. Unlike Serrano-Flores et al. [13], we did not acquire opercula regularly, which they used to facilitate gastropod presence and identification in the gut contents. ...
The whitespotted eagle ray (Aetobatus narinari) is a highly mobile, predatory batoid distributed throughout shallow, warm–temperate to tropical Atlantic Basin waters from North Carolina to Brazil. The species’ strong, plate-like dentition facilitates the consumption of hard-shelled prey, and due to effective winnowing behavior, it is a significant challenge to identify prey based on soft tissues alone. Here, we report on the first analysis of whitespotted eagle ray diet in Florida waters using visual-based gut content analysis complemented with DNA barcoding. Gut contents were obtained via gastric lavage from 50 individuals collected in the Indian River Lagoon and off Sarasota, Florida. Of the 211 unique prey samples collected, 167 were deemed suitable for sequencing. Approximately 56.3% of samples yielded positive species matches in genetic databases. Results from the sequenced data indicate that the whitespotted eagle ray diet in Florida is mainly comprised of bivalves and gastropods, with variable inclusion of crustaceans. Despite positive identification of venerid clams, there was no evidence for the consumption of hard clams (Mercenaria spp.), a major shellfish aquaculture and restoration species in Florida. Such wide-ranging prey species from various trophic guilds and locations highlight the whitespotted eagle ray’s diverse role in the top-down regulation of coastal benthic communities.
... cover netting) has been purported to effectively deter cownose ray predation on bivalves (Flimlin & Beal 1993), these conclusions are based on anecdotal reports, and, to our knowledge, no studies to date have assessed the effectiveness of these methods against other species of rays. The whitespotted eagle ray Aetobatus narinari, which is more restricted to tropical waters and attains larger sizes than cownose rays (Bigelow & Schroeder 1953), feeds on bivalves (Schluessel et al. 2010b, Ajemian et al. 2012, Serrano-Flores et al. 2019, Ajemian et al. 2021) and uses habitats within the vicinity of aquaculture leases in Florida's Indian River Lagoon (DeGroot et al. 2020). There, clammers periodically find crushed clams within anti-predator netting, questioning the effectiveness of this material against durophagous rays (E. ...
Shallow coastal waters are commonly used in shellfish aquaculture for ‘grow-out’ of bivalves like the hard clam Mercenaria mercenaria . These locations have substantially higher clam densities than the surrounding environment and attract molluscivores, requiring clammers to incorporate anti-predator materials into their grow-out gear to protect their product. However, the effectiveness of these materials against larger predators like rays remains untested. Inspired by clammer reports of predator-inflicted damage to grow-out gear, we assessed the capacity of the whitespotted eagle ray Aetobatus narinari to interact with clams housed within a suite of industry standard anti-predator materials. Mesocosm experiments were conducted where rays were exposed to unprotected clams (control), clams inside polyester mesh clam bags (dipped in a latex net coating and non-dipped), and under high density polyethylene (HDPE) or chicken wire cover netting. Gear interactions were quantified from video footage throughout the course of the experiment (5 h), and clam mortality was assessed after the completion of each trial. While rays were capable of consuming clams through bags, anti-predator treatments reduced clam mortality 4- to 10-fold compared to control plots. Double-layered (i.e. bags with cover netting) treatments had the lowest clam mortality (0.6 ± 0.1%; mean ± SE), highlighting the utility of this type of protection in limiting ray impacts. Though not significantly greater, we noted relatively high levels of interactions with HDPE netting over other materials, which was facilitated by the material ensnaring the lower dental plate of the rays. Clammers should consider adopting multi-layered anti-predator gear; however, resecuring materials periodically remains imperative at reducing ray interactions.
... The whitespotted eagle ray is a durophagous mesopredator feeding mainly on benthic invertebrates (Ajemian et al., 2012;Serrano-Flores et al., 2018) and is often found near coral reefs, along beaches and coastal inlets, and in estuarine seagrass habitats (Silliman & Gruber, 1999;Ajemian et al., 2012;Bassos-Hull et al., 2014;Flowers et al., 2017;Cerutti-Pereyra et al., 2018;DeGroot et al., 2020). Previously thought to be a single, globally distributed species in warm and tropical waters (Bigelow and Schroeder, 1953;Last et al., 2016) and the only species of its genus, A. narinari has been recently identified as a complex of several cryptic lineages: the genus Aetobatus (Blainville, 1816) currently comprises at least five known species, based on genetic and morphologic evidence (Richards et al., 2009;White, 2014;Sales et al., 2019), with the "true" A. narinari now restricted to the tropical Atlantic Ocean (Sales et al., 2019;Fricke et al., 2022). ...
... The whitespotted eagle ray is a durophagous mesopredator feeding mainly on benthic invertebrates (Ajemian et al., 2012;Serrano-Flores et al., 2018) and is often found near coral reefs, along beaches and coastal inlets, and in estuarine seagrass habitats (Silliman & Gruber, 1999;Ajemian et al., 2012;Bassos-Hull et al., 2014;Flowers et al., 2017;Cerutti-Pereyra et al., 2018;DeGroot et al., 2020). Previously thought to be a single, globally distributed species in warm and tropical waters (Bigelow and Schroeder, 1953;Last et al., 2016) and the only species of its genus, A. narinari has been recently identified as a complex of several cryptic lineages: the genus Aetobatus (Blainville, 1816) currently comprises at least five known species, based on genetic and morphologic evidence (Richards et al., 2009;White, 2014;Sales et al., 2019), with the "true" A. narinari now restricted to the tropical Atlantic Ocean (Sales et al., 2019;Fricke et al., 2022). ...
... A. narinari individuals were captured in the eastern Gulf of Mexico ("Gulf") through boat-based surveys (n=321) conducted between July 2009 and November 2019 along the southwest Florida coast ( Figure 1A). This area consists mostly of fringing barrier islands and shallow passes and inlets (200-2,500 m wide, < 20 m deep), which shelter various invertebrates that are potential prey for A. narinari: macrogastropods such as whelks and conch, and bivalves such as scallops and clams (Ajemian et al., 2012;Serrano-Flores et al., 2018). Sampling occurred primarily between north Longboat Key (latitude 27.4°N, longitude −82.7°W) and south Siesta Key (latitude 27.2°N, longitude −82.5°W) ( Figure 1B), predominantly April through November each year. ...
Elasmobranchs typically display slow growth, late maturity and low fecundity life history characteristics, making them vulnerable to fishing pressures and environmental perturbations. The whitespotted eagle ray (Aetobatus narinari), a large pelagic migratory ray with an endangered status on the IUCN Red List, fits this pattern based on available literature. Historically, age and growth parameters for this ray have been reported through vertebral ageing methods. However, the periodicity of vertebrate band pair formation, which is used for ageing, has not been validated for this species, making ageing accuracy and thus the resulting growth parameters uncertain. In this study, we used both a frequentist and Bayesian method of estimating sex-specific von Bertalanffy growth parameters (DW ∞, k) in wild recaptured versus aquarium-housed rays. Additionally, we estimated growth from repeated measurement data collected from aquarium-housed rays, as an alternative approach to obtain growth parameters while allowing for individual variability. Between 2009 and 2020, 589 whitespotted eagle rays were caught, measured, tagged and released along the southwest coast of Florida. Of these rays, 34 were recaptured between 5–1413 days at liberty. Nineteen additional rays were collected during the same period, transported and maintained at Georgia Aquarium, Atlanta, where they were regularly weighted and measured. Data from Association of Zoos and Aquariums accredited facilities provided prior information on maximum size for the Bayesian estimations, and size at birth, size at maturity, and maximum life span. These data were used to plot and interpret von Bertalanffy growth curves. Wild whitespotted eagle rays were found to grow faster and mature earlier than previously thought, with Bayesian estimates of k = 0.28 year⁻¹ in females, and k = 0.30 year⁻¹ in males. Aquarium-housed individuals seemed to grow slower and reach smaller sizes, although data provided by the aquariums showed variable growth patterns depending on the facility. Longevity was estimated at 14-15 years in wild rays while maximum lifespan observed in aquariums was 19-20+ years. Life history parameters and growth trajectories generated from this study offer valuable information to aid with future conservation management strategies of this endangered species.
... In some cases, an entire sample site was covered in "potholes". Spotted eagle rays are abundant in Bermuda (Ajemian et al. 2012) and one of the most common forms of bycatch during turtle sampling (at least 52 records). There has been concern expressed about the impact of large numbers of rays on the molluscan fauna of Bermuda (Ajemian et al. 2012), but the impact of rays on seagrass meadows has not been assessed. ...
... Spotted eagle rays are abundant in Bermuda (Ajemian et al. 2012) and one of the most common forms of bycatch during turtle sampling (at least 52 records). There has been concern expressed about the impact of large numbers of rays on the molluscan fauna of Bermuda (Ajemian et al. 2012), but the impact of rays on seagrass meadows has not been assessed. ...
To understand the demographic responses of green turtles to seagrass decline, we examined a data set from study of a mixed-stock foraging aggregation of immature green turtles, Chelonia mydas, collected in Bermuda (32o18’N, − 64o46’W) over five decades. Average turtle size (SCLmin) and mass declined by 22.3% and 58.2%, respectively. Aggregation size structure shifted to smaller sizes and now consists of more small turtles and fewer large turtles. Density (turtles ha⁻¹) increased significantly but biomass (kg ha⁻¹) remained unchanged and low compared to C. mydas biomass observed elsewhere. Green turtles exhibited reduced site fidelity during two portions of the study period, suggesting increased foraging effort. Reduction in turtle body condition index and seagrass coverage occurred from offshore to inshore. Changes in aggregation composition and behavior were consistent with expectations given a documented decline in seagrass availability, combined with increased output from source rookeries. Apparent response to resource decline is traced back to 1976, well before seagrass loss was first documented. Green turtles and their primary food source (Thalassia testudinum) are at the northern limit of their range in Bermuda, where seagrasses would be expected to have a reduced tolerance for natural grazing pressure and increased susceptibility to synergistic stressors, especially temperature, bioturbation and phosphorus limitation. Our results suggest that synergistic stressors, and not green turtles alone, have produced the observed reduction in seagrasses on the Bermuda Platform. Given that seagrass declines have been reported worldwide, our findings may suggest how green turtles will respond elsewhere.
... Whitespotted eagle rays (Aetobatus narinari) are mesopredatory batoids that play a key role in tropical and warm-temperate coastal water food webs, filling an intermediate position where this species acts as both predator (consuming gastropods and other benthic mollusks) [24,25] and prey (for sharks and marine mammals) [26,27]. Whitespotted eagle ray populations have largely declined due to overfishing and bycatch [28][29][30][31][32][33], and the species is now considered endangered by the International Union for Conservation of Nature. ...
Background
Animal-associated microbiomes can be influenced by both host and environmental factors. Comparing wild animals to those in zoos or aquariums can help disentangle the effects of host versus environmental factors, while also testing whether managed conditions foster a ‘natural’ host microbiome. Focusing on an endangered elasmobranch species—the whitespotted eagle ray Aetobatus narinari—we compared the skin, gill, and cloaca microbiomes of wild individuals to those at Georgia Aquarium. Whitespotted eagle ray microbiomes from Georgia Aquarium were also compared to those of cownose rays (Rhinoptera bonasus) in the same exhibit, allowing us to explore the effect of host identity on the ray microbiome.
Results
Long-term veterinary monitoring indicated that the rays in managed care did not have a history of disease and maintained health parameters consistent with those of wild individuals, with one exception. Aquarium whitespotted eagle rays were regularly treated to control parasite loads, but the effects on animal health were subclinical. Microbiome α- and β-diversity differed between wild versus aquarium whitespotted eagle rays at all body sites, with α-diversity significantly higher in wild individuals. β-diversity differences in wild versus aquarium whitespotted eagle rays were greater for skin and gill microbiomes compared to those of the cloaca. At each body site, we also detected microbial taxa shared between wild and aquarium eagle rays. Additionally, the cloaca, skin, and gill microbiomes of aquarium eagle rays differed from those of cownose rays in the same exhibit. Potentially pathogenic bacteria were at low abundance in all wild and aquarium rays.
Conclusion
For whitespotted eagle rays, managed care was associated with a microbiome differing significantly from that of wild individuals. These differences were not absolute, as the microbiome of aquarium rays shared members with that of wild counterparts and was distinct from that of a cohabitating ray species. Eagle rays under managed care appear healthy, suggesting that their microbiomes are not associated with compromised host health. However, the ray microbiome is dynamic, differing with both environmental factors and host identity. Monitoring of aquarium ray microbiomes over time may identify taxonomic patterns that co-vary with host health.
... The whitespotted eagle ray, Aetobatus narinari (Euphrasen 1970), is reported in the western Atlantic from North Carolina to southeastern Brazil (Bigelow & Schroeder, 1953), occupying coastal areas as bays, coral reefs and estuaries (Tagliafico et al., 2012) at depths of up to 60 m (Ajemian et al., 2012). Along the Brazilian coast the species has been recorded from 4 N to 22 S in coast as in oceanic islands (Sales et al., 2019). ...
The present study analysed aspects of reproductive biology based on macroscopic and microscopic structures of whitespotted eagle ray Aetobatus narinari captured by artisanal fishing off the coast of Paraíba and Pernambuco (7° 30′ S, 34° 49′ W; 7° 47′ S, 34° 51′ W), northeast Brazil. Of the 71 individuals in the sample, 55% were female (disc width – WD: 532–1698 mm) and 45% were male (WD: 442–1410 mm). The body size at which 50% of the individuals are mature (WD50) for males was 1155.8 mm; the clasper length varied between 24 and 184 mm. The WD50 for females was 1293.9 mm; the diameter of the largest vitellogenic follicle varied between 11 and 31 mm; and only the left ovary and uterus were functional. The microanatomy of the reproductive tract of males and females agrees with that of other elasmobranch species. In males, the highest hepato‐somatic index (IH) average and gonado‐somatic index (IG) average occurred in the third bimester of the year, whereas in females the highest values (average IH and IG, respectively) were in the second bimester of the year. Based on the information on reproduction of A. narinari from this study, it will be possible to contribute to the correct management and protection of this species.
... Despite the heterogeneous survey effort, the current method suggests a widespread distribution of eagle rays across a variety of coral reef habitats, which is in accordance with previous study (Ajemian and Powers, 2014). Future studies should seek to quantify habitat preferences of eagle rays by linking effortcorrected encounter rates to local habitat information (Ajemian et al., 2012;DeGroot et al., 2020). ...
... Environmental DNA is also an innovative method at the species level that can be notably used to detect rare species including elasmobranchs (Boussarie et al., 2018). Coral lagoons are major habitats for eagle rays (DeGroot et al., 2020;Ajemian et al., 2012) and our aerial approach proved efficient for monitoring populations in these habitats. Our approach can be complemented by other methods (e.g., eDNA, acoustic telemetry) in habitats where eagle rays can occur (Ajemian and Powers, 2014;Sellas et al., 2015) but waters are deep or turbid. ...
Reliable and efficient techniques are urgently needed to monitor elasmobranch populations that face increasing threats worldwide. Aerial video-surveys provide precise and verifiable observations for the rapid assessment of species distribution and abundance in coral reefs, but the manual processing of videos is a major bottleneck for timely conservation applications. In this study, we applied deep learning for the automated detection and mapping of vulnerable eagle rays from aerial videos. A light aircraft dedicated to touristic flights allowed us to collect 42 h of aerial video footage over a shallow coral lagoon in New Caledonia (Southwest Pacific). We extracted the videos at a rate of one image per second before annotating them, yielding 314 images with eagle rays. We then trained a convolutional neural network with 80% of the eagle ray images and evaluated its accuracy on the remaining 20% (independent data sets). Our deep learning model detected 92% of the annotated eagle rays in a diversity of habitats and acquisition conditions across the studied coral lagoon. Our study offers a potential breakthrough for the monitoring of ray populations in coral reef ecosystems by providing a fast and accurate alternative to the manual processing of aerial videos. Our deep learning approach can be extended to the detection of other elasmobranchs and applied to systematic aerial surveys to not only detect individuals but also estimate species density in coral reef habitats.
... The whitespotted eagle ray is a benthopelagic species over continental and insular shelves from the surface to 60 m depth, with a wide distribution throughout warm temperate to tropical waters (Last et al., 2016). This is a large, highly migratory ray species, which exhibits multiyear site fidelity and performs long-distance movement patterns (Ajemian et al., 2012;Bassos-Hull et al., 2014). The whitespotted eagle ray is currently listed as Endangered by the IUCN Red List, mainly due to its vulnerability to both targeted and nontargeted fisheries (Dulvy et al., 2021). ...
Here we provide the first photographic records of the eye healing of a free‐ranging whitespotted eagle ray (Aetobatus narinari) following shark‐inflicted bite injuries on the cephalic region. The whitespotted eagle ray with fresh wounds on the cephalic region close to its right orbit, upper jaw and the anterior margin of its right pectoral fin was photographed on 19 July 2017 at the Fernando de Noronha Archipelago. Two subsequent photographs of the whitespotted eagle ray with a blind right eye were taken on 29 March 2018 and 18 April 2018. These records show the whitespotted eagle ray had the capacity to recover from the wounds, although they have led to the blindness of the eye. These findings also demonstrate this individual was able to survive for at least 9 months with a nonfunctional eye.
