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The Mexican Caribbean is in one of the regions with the greatest diversity of elasmobranchs in the world. However, the population status of most of the shark and ray species in this region is unknown. We used a citizen science program based on divers to collect data about the diversity, abundance, and distribution of elasmobranchs in this region. We visited dive centers in six locations and performed structured interviews with divemasters, instructors, and owners of the diving centers. In total, 79 divers were interviewed, of which 69% had more than five years’ experience diving in the Mexican Caribbean. Divers could identify 24 elasmobranch species for this region. Most of the divers (82%) reported a decrease in sightings of sharks and rays. Rays were the most frequently sighted species by divers (89%), and the spotted eagle ray (A. narinari) was the most common elasmobranch species reported in the region. Citizen science was a useful approach gathering for baseline information about sharks and rays in the Mexican Caribbean, increasing our knowledge of the abundance and distribution of some species in this region. Citizen science affords the opportunity to obtain long-term data that can be useful for management and conservation.

Understanding predator–prey relationships is critical in ecology, but relatively challenging when investigating elusive marine megafauna. In this study, we document the presence of shark-inflicted ...

Antillean manatees in the Hondo River have been recorded from aerial and aquatic surveys, and interviews. However, these studies have been conducted only in the lower riverbed, leaving a gap of information about their presence and habitat characteristics in the rest of the river. We characterize and determine the ecohydrological variables influencing the presence and habitat use of manatees in the Hondo River. During 2017 and 2018, 30 based-boat field trips were conducted in five consecutive transects of 15 km each. A mixed methodology was used for manatee detection: side-scan sonar, direct sightings, and feces collection. Ecohydrological variables were measured in all transects and fixed points. The survey effort was 136.5 h. We recorded 123 manatees: 47% were observations during the boat-based surveys, 29% were at fixed points, and 24% were opportunistic. Additionally, 10 manatee feces were found. The first transect of the river showed the highest relative abundance for the two sampled seasons (windy = 0.27 manatees/km, dry = 0.55 manatees/km). According to the Poisson model, the estimated population was equal to 51 manatees. A random forest model suggested high probability of observing manatees in the first transects and decreasing at the upstream. The ecohydrological variables influencing the detection of manatees were conductivity, transparency, depth, and proximity to the Four Mile lagoon. The first two transects have ecohydrological characteristics that makes a benign environment for refuge, rest and feeding of manatees. We recommend carrying out conservation efforts in the first transects, such as protection and the regulation of boat transit.

Population assessments and species monitoring for many endangered marine megafauna are limited by the challenges of identifying and tracking individuals that live underwater in remote and sometimes inaccessible areas. Manatees can acquire scars from watercraft injury and other incidences that can be used to identify individuals. Here we describe a novel method for photo-identification of Antillean manatees Trichechus manatus manatus using aerial imagery captured during flights with a small multirotor drone. Between 2016 and 2017, we conducted 103 flights to detect and observe manatees in Belize, primarily at St. George’s Caye (SGC) near the Belize Barrier Reef. Review of aerial videos from these flights resulted in 279 sightings of manatees (245 adults, 34 calves). High-resolution images of individual manatees were extracted and classified according to image quality and distinctiveness of individual manatees for photo-identification. High-quality images of manatees classified as sufficiently distinctive were used to create a catalog of 17 identifiable individuals. At SGC, 21% of all sighted adult manatees (N = 214) were considered photo-identifiable over time. We suggest that the method can be used for investigating individual site fidelity, habitat use, and behavior of manatee populations. Our photo-identification protocol has the potential to improve long-term monitoring of Antillean manatees in Belize and can be applied throughout clear, shallow waters in the Caribbean and elsewhere.

Oral pathological conditions are common in mammals and have been relatively well documented for some wild groups, but are rarely reported in marine mammals. Here, we report for the Mexican Caribbean the first case of mandibular osteomyelitis in a free-ranging dolphin. A bottlenose dolphin Tursiops truncatus adult male (256.5 cm total length) was found stranded dead in the west coast of the State Reserve “Chetumal Bay Manatee Sanctuary”. Herein, we discuss some plausible explanations about the origin of this lesion to improve the knowledge about the species biology.

The Neotropical otter Lontra longicaudis is one of the least studied mammals of the Yucatán Peninsula and its presence in some water bodies of this region is questionable. Laguna Bacalar is the largest freshwater body located in the Yucatán Peninsula and faces several conservation problems due to its high potential for tourism development. We confirmed the presence of L. longicaudis in Laguna Bacalar by conducting interviews with residents, and the search for direct (sightings) and indirect (e.g., footprints) evidence of the species in 2013. We also include recent direct and indirect evidence (2019-2020). We classified the records into levels of certainty, according to the type of evidence (photographs, videos). We obtained 9 records of Neotropical otter through interviews (level 3), 3 sightings and 4 footprints (level 1), and 4 sightings (3 of these with level 2 and 1 with level 3 of certainty). It is necessary to increase the research effort to determine the conservation status and distribution of the Neotropical otter in the lagoon. We recommend making efforts in terms of socialization and education to facilitate the conservation of the Neotropical otters and their habitat in Laguna Bacalar.

Primary producers in the aquatic community structure are fundamental elements because they are the first link in the trophic network as occur in most ecosystems. They produce oxygen and biomass, act as a shelter for several species, and provide food for a wide variety of megaherbivore species like manatees and sea turtles. Physicochemical processes taken place in primary producers can be determined through stable isotope analysis (SIA) as natural tracers from elements like carbon and nitrogen, applied in ecological, and physiological studies. In the Mexican Caribbean ecosystems, SIA has been little applied in aquatic plants, where Thalassia testudinum is the main seagrass species studied. Here, we present the isotopic composition (δC and δN) from 95 aquatic and semiaquatic plant species of four vegetation types, from three different environments, hydroclimatic seasons, and geographical zones in the Mexican Caribbean. Main statistical differences in δC and δN were found according to vegetation type and environment. Besides, for δC were also found statistical differences among seasons, while for δN differences were found among zones (H-Test, p < 0.05). This study provides an isotopic baseline for further ecological studies in the region. This information can contribute to understanding the structure of aquatic food webs and infer the diet and feedings habits of aquatic species, as well as to detect possible changes related to anthropogenic activities that can affect the survival of these plant species, and the fauna depending on them., This research was part of N. Garcés-Cuartas Ph.D. thesis from the Sustainable Development Program from the University of Quintana Roo , Mexico, who benefited from CONACYT (Consejo Nacional de Ciencia y Tecnología) graduate fellowship. Logistics at the sampling surveys were partially funded by PADI Foundation (Program: Mammals, Turtles and Birds. App # 28521 ). Laboratory analysis was covered by PRODEP (Mexico), and the Stable Isotopes Biogeochemistry Laboratory from the Instituto Andaluz de Ciencias de la Tierra in Granada (Spain). We especially thank Arsenio Granados Torres for the stable isotope analysis of plant samples. We want to thank the advisors P. Blanco-Parra and P. Barradas-Miranda for their comments to previous versions of this work. Also, we thank Dr. Beth Brady for the document review, as well as two anonymous reviewers for the very helpful suggestions that improved this manuscript. The funders had no role in study design, data analysis, decision to publish or preparation of the manuscript. This research was part of the Monitoring Program of Aquatic Megafauna from the Mexican Caribbean (PROMMAC) (permit: SGPA/DGVS/006294/18 ).

Background. Until 2015, the aquatic mammal’s biodiversity in the Mexican Caribbean was unknown, but was in that year when 18 species were confirmed to be distribute in this region, none of them a Rorcual species. Goals. The aim of this work is to report the first sighting of a Balaenopteridae whale in the Mexican Caribbean. Methods. CONANP patrolling activities at the National Park Isla Contoy were conduced. Results On 2th August 2018, a stranded-live whale was found. The animal was identified as a ~18m (in length) fin whale Balaenoptera physalus (Linnaeus, 1758). Conclusions. This note is the first confirmed record of this species in the Mexican Caribbean increasing the list of confirmed aquatic mammal species distributed in this region.

Abstract The Caribbean is a mega-diverse and bio-geographically important region that consists of the Caribbean Sea, its islands, and surrounding coastlines. Among the billions of aquatic species inhabiting this region, the mega-vertebrates stand out for their social, economic and ecologic relevance. However, the Caribbean has been threatened by climate change, poverty, pollution, environmental degradation and intense growth of the tourism industry, affecting megafauna species directly and indirectly. Population monitoring plays a critical role in an informed conservation process and helps guide management decisions at several scales. The aim of the present review was to critically examine the methods employed for monitoring marine megafauna in the Caribbean, so as to create a framework for future monitoring efforts. In total, 235 documents describing protocols for the monitoring of sirenians, cetaceans, elasmobranchs, sea turtles and crocodilians in the Caribbean region, were reviewed. The methods included community-based monitoring (interviews, citizen science and fisheries monitoring), aerial surveys (by manned and unmanned aerial vehicles), boat-based surveys (including manta tow, and side-scan sonars), land-based surveys, acoustic monitoring, underwater surveys, baited remote underwater video, mark–recapture, photo-identification and telemetry. Monitoring efforts invested on aquatic megafauna in the Caribbean have been highly different, with some species and/or groups being prioritised over others. The present critical review provides a country-based overview of the current and emerging methods for monitoring marine megafauna and a critical evaluation of their known advantages, disadvantages and biases.

The feeding ecology and trophic level of the banded guitarfish, Zapteryx exasperata, from the Gulf of California, were assessed using stable isotope analysis (SIA) of carbon and nitrogen in muscle samples, and stomach contents analysis (SCA). Males and females showed similar diet preferences with a high diet overlap (Cλ = 0.99) and similar values of δ13C and δ15N (ANOVA, F = 0.0 p = 0.94 for δ13C; F = 0.1 p = 0.78 for δ15N). The main prey groups found were demersal fishes dominated by the daisy midshipman, Porichthys margaritatus, (>90%IRI), however, pelagic fishes were also found (Engraulis mordax 2%IRI). An ontogenetic diet shift was found, indicated by the importance of crustaceans in the juvenile diet and the significant isotopic differences between juveniles and adults (δ13C, ANOVA, F = 13.3 p = 0.0004 and δ15N, ANOVA, F = 4.7 p = 0.03). An overall trend of increase in δ15N values with increasing body length (F = 8.15 p = 0.005) was observed. The mean trophic level estimated in this work by the two methods was ~4.1, indicating that this species is a top predator in the Gulf of California. Zapteryx exasperata is a specialist feeder (Bi = 0.11, H’ = 2.32), consuming mainly benthic fishes in coastal areas of the Gulf of California. The importance of this species in the benthic ecosystem equilibrium as a top predator is an important point to keep in mind when developing future management plans of the batoid fishery in the Gulf of California.

The present study reports unique data on concentrations of several classes of organochlorine pesticides and polychlorinated biphenyls in blubber biopsies from healthy living fin whales (Balaenoptera physalus) from the Gulf of California, Mexico, one of the most isolated and unstudied population in the world. OC levels in this population were generally lower than levels reported in fin whales from other regions. The rank order of OCs were ∑DDTs (range from 300 to 2400 ng g−1 lw) > ∑PCBs (range from 40 to 290 ng g−1 lw) > ∑HCHs (range from

We report concentrations of several classes of organochlorines (OCs) in the blubber of California sea lions (Zalophus californianus) from the Gulf of California. Summed OC levels measured in 34 wild-ranging animals were, in general, lower than those previously reported in sea lions from the eastern Pacific. The rank order of OCs was SigmaDDTs (mean=3400 ng g(-1 ) lipid weight [lw])SigmaPCBs (1400 ng g(-1 ) lw)SigmaHCHs (50 ng g(-1 ) lw)or= SigmaCHLORs (46 ng g(-1 ) lw). The most abundant OC measured was the DDT metabolite, p,p'-DDE. No significant differences in OC profiles were found between genders or rookeries. Although the mean concentrations of OCs measured in adult males and females were similar, only adult females had significantly higher (p0.05) mean blubber concentrations of summation SigmaDDTs and summation SigmaHCHs than pups.

Stable isotopic analyses of carbon, nitrogen, and sulfur were performed on teeth of different ages and sexes of the longbeaked common dolphin, Delphinus capensis, from the Gulf of California. Similarities in diet are suggested between the sexes, with no significant differences in isotopic compositions being observed. Differences in the δ 13 C, δ 15 N, and δ 34 S signatures were found among the age groups (nursing calf, juvenile, subadult, and adult). These data suggest that this species is generally a coastal feeder, and that it changes its feeding habits with increasing age, drawing more nutrition from higher trophic level organisms later in life.

The main objective of this study was to apply a set of sensitive non-lethal biomarkers in skin biopsies of fin whales (Balaenoptera physalus) to evaluate the toxicological status of this mysticete in the Pelagos Sanctuary (Mediterranean Sea) and in the Gulf of California (Sea of Cortez-Mexico). We developed a "multi-trial diagnostic tool" (based on field and in vitro studies), combining molecular biomarkers (western blot of CYP1A1, CYP2B) and gene expression (qRT-PCR of HSP70, ERα, AHR, E2F-1) with the analysis of OCs, PAHs and PBDEs. The study revealed a higher level of toxicological stress in the Mediterranean fin whales.