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Diagram of various attachment points and techniques for tethering towed-float SPOT5 transmitters to myliobatid rays. Symbols indicate the tether type and locations relative to a silhouette of a Cownose (left) and Spotted Eagle Ray (right). Symbols are superimposed on photographs of individuals fitted with transmitters in the field
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Batoids are important mesopredators whose high mobility and extensive migrations can link seemingly distant food webs in coastal ecosystems. Despite this recognition, our knowledge of the movement patterns of many species is limited due to the logistical challenge of tracking these animals on multiple scales. Smart Positioning or Temperature (SPOT)...
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... determine the feasibility of using Wildlife Computers © SPOT5 towed-float tags on myliobatid stingrays, we conducted an initial captive study using Cownose Rays. Mature Cownose Rays [ n =21; >80 cm disc width (DW); 8 – 15 kg; Neer and Thompson 2005] were captured from local nearshore waters of the Mobile and Perdido Bay estuaries and transported in plastic tubs of ambient seawater to the Claude Peteet Mariculture Center in Gulf Shores, Alabama. All rays were kept in a single 50 × 25 m pond with free-flowing seawater pumped from the nearby Gulf of Mexico. During the 30 day study period, pond temperatures ranged from 25 to 30 °C and salinities were generally 30 psu. Pond depth ranged from 0.5 to 2.0 m with a bottom mainly composed of mixed sand and silt. Rays were fed to satiation daily with a mixture of cut fish and shrimp. Eleven rays were fitted with non-functional versions of SPOT5 towed-float tags and allowed to swim freely around the experimental pond with ten “ control ” rays, which received no tag treatment. Tags were secured to the rays using one of five methods: 1) Spiracular Tube, 2) Dart Bridle, 3) Tail Suture; or 4) Through-wing Disc- bridle (Fig. 1). Spiracular attachments (method 1) involved a segment of Silastic TM tube that ran through the most medial portion of the spiracular cartilage and lat- erally across the dorsal region of buccal cavity and around the head. A strand of monofilament was run through the inside of the tube and crimped to a swivel above the head to secure the tether attachment. This design kept the attachment medial to spiracular open- ings and allowed for uninhibited movement of the valves during respiration. Dart bridles (method 2) were inserted into the dorsal musculature of the rays ’ pectoral fin in the “ trunk ” region posterior to the spiracles and anterior to the dorsal side of the peritoneal cavity. Tail sutures (method 3) also utilized a segment of monofilament inside a tube that was inserted around the base of the tail, medial to the pectoral fin insertion and crimped back on itself on the dorsal side anterior to the dorsal fin. Through-wing disc bridles (method 4) involved the same Silastic TM and monofilament material run dorso- ventrally through the pectoral fin. Tubes were secured to the exterior portion of the pectoral fin using neoprene discs and crimps. Monofilament bridles were crimped to the main swivel and tag attachment. All tethers were connected to the transmitter via a double-barrel swivel with a 50 cm length of coated aircraft cable (54 kg breaking strength) provided by the manufacturer. During the trial period, animals were checked daily for behavioral changes and photographed, measured, and inspected on a weekly basis. We noted initial scar- ring around dart tag insertion sites, but these generally healed within a week. No mortality associated with tagging treatment was observed over the 30 day period. Furthermore, all tagged and control rays continued to school together and exhibited normal behaviors. Due to species-specific differences in head morphology and overall size, for field deployments we elected to use spiracular attachments on Cownose Rays only and restricted through-wing disc attachments to much larger and thicker-bodied Spotted Eagle ...
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The diversity and specific composition of zooplankton communities have a direct effect on the ecosystem services (e.g., carbon export) and structure of ocean food webs. In areas where diversity is high, a detailed characterization of the whole community can represent a hurdle that prevents a complete understanding of those processes and interaction...
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... 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]. ...
... In Bermuda, wintertime temperatures can approach 15 • C within shallow inshore bays (1), which could force rays to become migratory. However, since those conditions do not last for long periods, it is possible rays simply move to warmer waters in the North Lagoon, similar to the pattern observed in the northern Gulf of Mexico (9,24), or are resident, as reported in parts of south Florida (25,26). Along the Atlantic coast of the U.S., northward migration cues for females and males depend on different factors: sea surface temperature for females, and day of year for males (22). ...
... 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.
... 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). ...
... De esta manera, la investigación espacio-temporal de los movimientos de elasmobranquios, así como la función de los hábitats que utilizan, es esencial para evaluar la interacción entre elasmobranquios y actividades humanas (Becerril-García et al., 2022). En los a aetobátidos se ha documentado residencia permanente y estacional en determinadas zonas costeras (Flowers et al., 2016), relacionadas a su alimentación (Ajemian et al., 2012;Ajemian y Powers, 2014) por lo que el desarrollo de actividades humanas no reguladas puede tener un impacto de manera directo o indirecta en sus poblaciones. ...
... narinari, la cual presenta residencia en la laguna costera Indian River (costa oriental de Florida) y las costas de Bermudas (Ajemian et al., 2012;Ajemian y Powers, 2014;Degroot et al., 2021); en cambio, la misma especie presenta fidelidad interanual en Bahía de Sarasota (costa occidental de Florida), regresando año con año durante las estaciones de primavera y verano, siendo la temperatura el principal factor con influencia en sus movimientos (Bassos-Hull et al., 2014;Degroot et al., 2021). Por otro lado, en el Caribe algunos individuos presentaron fidelidad al sitio, con reavistamientos en una sola estación y solo dos ejemplares se observaron en años consecutivos en la misma área (Cerutti-Pereyra et al., 2017). ...
... The advent of electronic pop-up satellite archival tags (PSATs) has allowed for better understanding of the vertical habitat use and diving behavior of large open-ocean species as they can allow for tagged animals to be studied without having them remain within the confines of a receiver array or requiring personnel and resources to actively track and recapture the animals (Sims 2010). Electronic tags have been used to investigate movements of batoids such as the common skate, Dipturus batis (Wearmouth and Sims 2009), the Arctic skate, Amblyraja hyperborea (Peklova et al. 2014), big skates, Beringraja binoculata (Farrugia et al. 2016), thorny skates, Amblyraja radiata , cownose rays, Rhinoptera bonasus (Omori and Fisher 2017), reef manta rays, Mobula alfredi (Lassauce et al. 2020), and spotted eagle rays, Aetobatus narinari (Ajemian andPowers 2014, Brewster et al. 2021). However, Le Port et al. (2008) were the first to establish a successful method to attach PSATs to dasyatid stingrays, reporting information on the movements of short-tailed stingrays, Bathytoshia brevicaudata, for up to 150 days off the northeast coast of New Zealand. ...
The pelagic stingray, Pteroplatytrygon violacea , is commonly encountered as bycatch in pelagic longline fisheries targeting Swordfish, Xiphias gladius , and tunas; however, very little is known about its habitat use. To better assess the utility of the technology and attachment method, four pop-up satellite archival tags (PSATs) with short, 13-day durations were deployed on pelagic stingrays in 2010 and 2011 in the South Atlantic Bight (n = 2) and the northern Gulf of Mexico (n = 2). Analysis of the minimum straight-line distances from the first transmission locations compared to release locations showed that pelagic stingrays moved from 151.0 to 258.0 km [mean (SD) = 190.8 (46.6) km] or between 11.6 to 19.8 km day ⁻¹ . Data also indicates pelagic stingrays undergo small diel vertical migrations with stingrays inhabiting slightly warmer [20.95 (3.4) °C], shallower [128.6 (99.8) m] waters at night, compared to cooler [19.7 (3.0) °C], deeper [167.0 (112.4) m] waters during the day. Understanding habitat use and behavior of less economically important species, particularly those that compose a substantial portion of bycatch like pelagic stingrays, will help fisheries managers account for these interactions with more economically valuable target species, as well as advance the overall understanding of pelagic ecosystems and aid in conservation efforts.
... It is likely that these animals are staying within the IRL given the short durations between detections are not extensive enough to migrate to the northern extent of the Mid-Atlantic Bight, and thus would be using areas beyond the Sebastian receiver array. The most common detection period for a large majority of individuals was during the Fall of 2017, which is consistent with findings that cownose rays in southwest Florida were more frequently observed during the summer and fall months than during other seasons [59]. Within the study period, there were examples of synchronized movements in which cownose rays appeared to follow similar patterns when moving from September 2017 to January 2018, and again from March 2018 to June 2018. ...
... Previous research suggests that cownose rays are most active periodically throughout the day and for a few hours at night [59] while other studies suggest no diel patterns [13,57]; however, these apparent differences may be a result of using different tagging methodology, different study habitats, and potentially disparate populations with different behaviors. Our results suggested a slight association for more extended visits around late morning, which could align with foraging behaviors. ...
The Indian River Lagoon is a primary location of field-based "grow-out" for bivalve shellfish aquaculture along Florida's Atlantic coast. Grow-out locations have substantially higher clam densities than surrounding ambient sediment, potentially attracting mollusk predators to the area. Inspired by clammer reports of damaged grow-out gear, we used passive acoustic telemetry to examine the potential interactions between two highly mobile invertivores-whitespotted eagle rays (Aetobatus narinari) and cownose rays (Rhinoptera spp.)-and two clam lease sites in Sebastian, FL and compared these to nearby reference sites (Saint Sebastian River mouth, Sebastian Inlet) from 01 June 2017 to 31 May 2019. Clam lease detections accounted for 11.3% and 5.6% of total detections within the study period, for cownose and whitespotted eagle rays, respectively. Overall, the inlet sites logged the highest proportion of detections for whitespotted eagle rays (85.6%), while cownose rays (11.1%) did not use the inlet region extensively. However, both species had significantly more detections at the inlet receivers during the day, and on the lagoon receivers during the night. Both species exhibited long duration visits (> 17.1 min) to clam lease sites, with the longest visit being 387.5 min. These visit durations did not vary substantially between species, although there was individual variability. Based on generalized additive mixed models, longer visits were observed around 1000 and 1800 h for cownose and whitespotted eagle rays, respectively. Since 84% of all visits were from whitespotted eagle rays and these longer visits were significantly longer at night, this information suggests that observed interactions with the clam leases are potentially underestimated, given most clamming operations occur during daytime (i.e., morning). These results justify the need for continued monitoring of mobile invertivores in the region, including additional experimentation to assess behaviors (e.g., foraging) exhibited at the clam lease sites.
... While sample sizes were limited, no evidence for sex-related dietary differences in the studied species was detected, in agreement with the results from several studies of batoids (Jacobsen and Bennett 2013;Mulas et al. 2019). Other studies have, however, noticed that some batoid species exhibit differential diet and habitat use patterns between sexes (Ajemian and Powers 2014;White et al. 2014;Jargowsky et al. 2020;Serrano-Flores et al. 2021). ...
Abstract Describing the trophic structure and
interactions of demersal elasmobranch assemblages
is fundamental to understanding food web
dynamics and developing ecosystem-based management
approaches. Stomach content analysis
(SCA) and stable isotope ratios (SIA) of carbon
(δ13C) and nitrogen (δ15N) from muscle were
used to examine the dietary habits and intra- and
interspecific trophic ecology of three sympatric
batoid species (Dasyatis pastinaca, Raja clavata,
and Raja maderensis) from the Azores, Northeast
Atlantic. Data were analyzed with respect
to sex and maturity stages. SCA showed that D.
pastinaca feeds mostly on crustaceans, whereas R.
clavata and R. maderensis prey almost exclusively
on teleosts, but not on the same species. Dasyatis
pastinaca displayed higher δ13C and lower δ15N
values compared to R. clavata and R. maderensis.
Trophic niche breadth was variable, D. pastinaca
and R. clavata had the broadest and the narrowest
trophic breadth, respectively. Relative trophic
position categorized D. pastinaca as a mesopredator,
while R. clavata and R. maderensis occupied
higher trophic positions. With size, R. clavata
and R. maderensis shifted from small prey such
as crustaceans to larger prey such as teleosts, and
they also exhibited significant increases in δ15N
with size. Dietary and isotopic overlap was overall
low among species, but it was higher between
R. clavata and R. maderensis, suggesting more
similarity in diet and habitat use between them
than with D. pastinaca. This study depicts trophic
interactions and functional roles of three co-existing
batoid species in the Azorean food webs. In
addition to presenting new information on the
trophic ecology of D. pastinaca and R. clavata,
the present study provides, to our knowledge,
the first description of the diet composition and
trophic level of the Macaronesian endemic batoid
R. maderensis.
... Additionally, Capapé (1989) suggested that a competitive pressure in the same area between T. grabatus and other dasyatid species such as the large roughtail stingray Bathytoshia lata (Garman, 1880), that enhances its migrations. Ajemenian & Powers (2014) noted that batoid species are very mobile and prone to both large latudinal and vertical migrations. However, only the use of molecular tools could indicate whether or not different populations of T. grabatus occur in the Mediterranean Sea, including different regions of the Maghreb shore, central and eastern Mediterranean Sea, but also the eastern tropical Atlantic. ...
... Furthermore, knowledge on both local habitat use, as well as larger-scale habitat connectivity, is required to understand habitat dependence and the roles that rays may play within and across these habitats through ecological niche dynamics and energy flow (Beck et al. 2001;Murray et al. 2018;Frisk et al. 2019). Some pelagic rays have been found to be important in connecting different habitats such as islands, reefs and estuaries along continental shelves (for example Ajemian and Powers 2014;Braun et al. 2015;Ogburn et al. 2018;DeGroot et al. 2021). Conversely, benthic rays have only been shown to display site affinity to shallow and protected ecosystems, such as bays and estuaries (for example Cerutti-Pereyra et al. 2014;Davy et al. 2015;Brinton and Curran 2017), and it remains unclear whether these species may disperse from, or move between, these habitats (i.e. ...
The blue stingray Dasyatis chrysonota is an important and endemic coastal inhabitant of southern African coastal waters however, it is listed as Near Threatened with declining populations. Understanding it’s spatial ecology in the context of current Marine Protected Areas (MPAs) is vital to not only inform population dynamics and ecological roles, but to determine whether currently zoned MPAs can provide sufficient protection to this species. Twenty-seven individuals were monitored using the Acoustic Tracking Array Platform (ATAP—a nation-wide collaborative network of acoustic receivers) for up to 4.5 years. Individuals displayed site affinity to defined regions of the coast, with the majority of detections for most individuals being recorded in the shallow bay/coastal shelf they were tagged in. However, important movement corridors linking different habitats were also identified (inshore vs offshore and coastal bay vs coastal shelf habitats). This habitat use varied monthly and was influenced by temperature, with individuals displaying restricted movements to the shallow bay habitat in summer when deeper waters were much colder. The large collaborative nature of the ATAP allowed for the monitoring of a benthic ray across large spatial scales for the first time, challenging preconceived notions that small undulatory batoids cannot travel large distances (many individuals were found to travel up to 200 km). Insights can also assist in local management of this species, and highlight that current MPA zonation may not be sufficient to protect blue stingrays from further population declines.
... Effective conservation requires up-to-date and high quality data collected with limited monetary and human costs over repeated periods (Fust and Loos, 2020). Previous studies on the distribution and movements of eagle rays have relied on acoustic (DeGroot et al., 2020) and satellite telemetry (Ajemian and Powers, 2014). Active acoustic telemetry implies following the individuals in order to determine their movements in the water column, but is generally restricted to few individuals and necessitates a large array of hydrophones (DeGroot et al., 2020). ...
... Active acoustic telemetry implies following the individuals in order to determine their movements in the water column, but is generally restricted to few individuals and necessitates a large array of hydrophones (DeGroot et al., 2020). Satellite telemetry allows tracking rays over potentially large spatial scales, but is constrained by the frequency and precision of GPS data and associated costs (Ajemian and Powers, 2014). Both methods are intrusive as they require catching and manipulating individuals to attach the tags properly. ...
... Nevertheless, our accurate algorithm will be applicable to images collected along systematically-designed transects for abundance estimation in the future. 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). ...
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 main prey group for each family was similar in both the Pacific and Atlantic coasts; therefore, these batoids could be classified as strict specialists. The food selectivity in these species may be due to their greater mobility, large size, and pelagic and benthopelagic habits, which gives them a greater ability to search for prey from one area to another (Ajemian & Powers, 2014;Graham et al., 2012;Sellas et al., 2015), while smaller species, such as Rajiformes, with benthic habits and less mobility (Simpson et al., 2020), feed on different types of prey that are within their reach. . Species of Arhyncobatidae and Narcinidae switched from polychaetes to fishes (Cabrera-Meléndez, 2017;González et al., 2006;Rinewalt et al., 2007) or from bivalves to crustaceans in Rhinopteridae . ...
Batoid (rays and skates) populations are declining worldwide, with unknown ecological consequences due to lacking consolidated data on the trophic ecology of these species. Such trends are particularly disconcerting in Mexican waters, where batoids are heavily exploited by commercial fisheries. To assess the current state of knowledge of batoid diet in this region, we conducted a meta-analysis of 54 published stomach content analysis studies. Trophic niche was assessed from 44 total species, including variations due to sex, ontogeny, season, and region, as well as trophic overlap among species. The species assessed belonged to the taxonomic families Urotrygonidae, Dasyatidae, Potamotrygonidae, Mobulidae, Rhinopteridae, Aetobatidae, Gymnuridae, Rhinobatidae, Rajidae, Arhyncobatidae, and Narcinidae. Most of the diet studies to date were conducted in the Mexican Pacific (n = 24), whereas only three studies have come from the Mexican Atlantic, with 27 additional studies coming from other American countries from the tropical and subtropical region. Crustaceans were reported in more than 50% of the species assessed and were also generally the most important prey item, with either high (76%–100%) and medium-high (51%–75%) importance based on dietary indices from the literature reviewed. While the diet of 40 species (91%) consisted of more than one prey type, feeding strategy analysis (Levin and Shannon–Wiener indices) of 27 species indicated that 25 were specialists and two generalists. Species diets varied with ontogeny (20%), sex (11%), region (11%), and seasonality (9%). According to the reviewed studies, interspecific diet overlap was evident in 36% of species, mainly in the family Urotrygonidae. Batoids were grouped into four trophic guilds: crustacivores (68.1%), annelidivores (primarily polychaetes) (13.6%), molluscivores (11.3%), and piscivores (6.8%), based on the literature reviewed. This study showed that most of the batoids had a specialist crustacean-based diet. Future research should focus on species devoid of dietary data to encapsulate the trophic niche breadth of this group in Mexican waters, particularly from the Mexican Atlantic and surrounding regions.
... Contrasting with most of the other elasmobranchs we examined, C. limbatus and A. narinari, both showed increases with SST and El Niño conditions. These two species prefer high temperatures (Bassos-Hull et al., 2014;Lear et al., 2019), and are generally more resident species than the larger sharks and rays, with smaller home ranges and movements typically restrained to local reefs or sandflats (Ajemian & Powers, 2014;Yates et al., 2016). Thus, both species could be more tolerant of temperature extremes (Lear et al., 2019), and in fact, the positive effect of SST on C. limbatus occurrence was weak at Cocos. ...
... Carcharhinus limbatus sometimes spends time above its thermal optimum, likely to avoid predators or take advantage of foraging opportunities (Lear et al., 2019). Small myliobatid rays also use warm waters to increase metabolic rates while foraging (Ajemian & Powers, 2014;Matern et al., 2000), and A. narinari may be doing the same at Cocos. The occurrence of G. cuvier at Cocos also increased with rising SST, but with large uncertainty seen in 95% confidence intervals including zero. ...
... For instance, T. obesus exhibited large declines despite its lower mobility and lower catchability on longlines, and so the small negative effects of SST may have impacted its population fitness. However, the sharp declines in A. narinari relative abundance and its positive relationship to SST-being most abundant above 30℃-suggest fishing could be impacting their populations despite a generally high residency and site fidelity(Ajemian & Powers, 2014). We hypothesize that climate change and fisheries exploitation may be interacting to affect longterm trends. ...
Climate change is altering distributions and abundances of marine species through both gradual and acute changes in temperature and productivity. Due to their high mobility and metabolic rates, elasmobranchs (sharks and rays) are likely to redistribute across latitudes and depths as they thermoregulate, but little is known about their responses to these climatic changes, which could vary widely across this diverse group of species.
Here, we assessed how species with differing mobility and ecology responded to gradual changes in daily sea surface temperature (SST) and acute temperature anomalies, caused by the El Niño–Southern Oscillation (ENSO), at Cocos Island, Costa Rica, the site of multiple marine heatwaves.
We used generalized linear mixed models to analyse 34,342 records of relative abundance or frequency of occurrence for seven shark and ray species collected in 27 years (1993–2019) by a dive company. We compared effect sizes for SST and the Oceanic Niño Index across the different species, which vary widely in body size and mobility.
Large, mobile species responded strongly but inconsistently to temperature. For scalloped hammerhead sharks Sphyrna lewini, a 1℃ rise in SST reduced counts by over 14%, and dropped the occurrence of their large schools by almost one‐fifth (19.4%). Mobula ray occurrence also declined substantially with a few degrees rise in SST, whereas tiger shark Galeocerdo cuvier occurrence sharply increased. These species also had divergent responses to the ENSO: S. lewini and G. cuvier were sighted with greater frequency during La Niña events, and their abundance dropped considerably during El Niño events—over a twofold decline between a strong La Niña and strong El Niño for S. lewini. In contrast, Mobula rays showed little response to ENSO. The smaller and sedentary Triaenodon obesus exhibited the weakest response of all species to both SST and the ENSO, reflecting its lower metabolic rates and mobility.
Climate change will continue to impact elasmobranchs, even for smaller and more localized species, with the potential to impact the effectiveness of marine protected areas (MPAs). Our results compel further work on the diversity of elasmobranch responses to environmental change.
