Holbox Research Articles

Microsatellite Loci of the Atlantic Horseshoe Crab (Limulus polyphemus) Reveal Inter-Localities Genetic Diversity in the Coastal Waters of the Eastern and Northern Yucatan Peninsula.

The American horseshoe crab (Limulus polyphemus) is an economically and ecologically important species, which is currently categorized as endangered in Mexico. L. polyphemus, one of four extant horseshoe crab species that constitute the class Merostomata, is distributed along the Atlantic coastline of the USA from Alabama to Maine and has another population on the coastline of Campeche, Yucatan, and Quintana Roo in the Yucatan Peninsula, Mexico. In the present study, we evaluated the genetic diversity and genetic structure of four separated localities along the coast of the Yucatan peninsula (Champoton, CH; Isla Arena, IA; Rio Lagartos, RL; and Holbox Island, HI), using nine microsatellite-type molecular markers for this species. The aim of this study is to obtain a baseline of the current level of genetic diversity, which would allow the monitoring of important changes over time. Multilocus analyses revealed moderate levels of genetic diversity (He, 0.5230 to 0.6389) and genetic structure within the whole study area (FST 0.025). The population from RL showed limited gene flows, differing significantly from the other sampling sites. The genetic information obtained in this study can support the implementation of management and conservation programs for this species in Mexico.

Solid waste and microplastics on the beaches of Holbox island, Mexico

Solid waste (SW) and microplastics (MP) are present in different parts of the marine and coastal environment, including remote areas such as islands. In the Mexican Caribbean, there are around 87 islands that are characterized by their white sand beaches, blue sea, and vast diversity of flora and fauna; protected natural areas have been established in some of these islands to preserve ecosystems and their integral functions. This research aimed to study the presence of MP, SW, and plastic containers (PC) on the Mexican island “Holbox”, which is part of the Yum Balam protected area. The MP were studied in three beach areas of the urban area with different tourist influx, SW was studied in a beach area with high tourist influx, and the PC were studied in a virgin beach. The mean concentration of MP and SW was 49.37 ± 45.55 MP/m2 and 0.116 ± 0.023 pieces/m2, respectively. On the virgin beach of the island, 72 plastic containers were found, 28 of which came from other countries, mainly from the Caribbean islands. The results provide information on marine pollution by SW, MP, and PC on Holbox island; all these kinds of waste can come from unsuitable waste management in the island (in the dumpsite) or be transported to the island by marine currents.

Tourists perceptions of Caribbean islands facing environmental threats before the COVID-19 health crisis: Holbox Island and Archipelago of Bocas del Toro.

Knowledge gaps exist in the socio-ecological systems of small touristic islands in Latin America. Understanding tourists' perceptions of their environmental knowledge can help plan actions to prevent natural capital loss necessary for local economies. Tourists' perceptions of a touristic hotspot, Holbox Island, were documented. Surveys demonstrated that tourists are aware of their environmental impacts and are interested in minimizing these. Results were compared with results on Bocas del Toro, Panama. Tourists' perceptions had similarities among sites driven by similarities in tourists' populations with a common geographic origin. Tourists lack site-specific knowledge to steer them towards environmentally conscious decisions in both regions. Findings suggest the need to promote local actions to gain tourists' understanding about their destination and support education programs on island conservation. Addressing these needs can help build resilience to overcome the adverse socio-environmental effects of tourism, environmental disasters, and health crises as COVID-19 on small islands.

Incidence of 49 elements in the blood and scute tissues of nesting hawksbill turtles (Eretmochelys imbricata) in Holbox Island

Due to progressive urban development along the Mexican Caribbean coastline, it is crucial to gauge the impact of anthropogenic contamination of marine ecosystems through biomonitoring procedures. In the current study, we quantified the concentration of 49 inorganic elements in the blood and scute tissues of clinically healthy nesting hawksbill sea turtles (Eretmochelys imbricata). The elements were classified into four groups: Group A: essential mineral elements with toxic potential; Group B: non-essential elements with high toxicity; Group C: toxic non-essential minority elements and Trace Elements (TE); and Group D: rare-earth elements (REE) and other TE. Almost all the samples in both tissues showed perceptible levels of all the quantified elements. The only element identified with a correlation between blood and scute was arsenic (As), which could indicate a fast excretion through this type of keratinized tissue. The bio-accumulation of inorganic elements is a complex process, requiring the simultaneous examination of different tissues to evaluate the exposure. Our study reinforces the usefulness of scute tissue as a non-invasive sampling technique for the evaluation of persistent pollutants in marine turtles.

Characterization of Flowpath Using Geochemistry and 87Sr/86Sr Isotope Ratios in the Yalahau Region, Yucatan Peninsula, Mexico

The Yalahau region, located in the northeastern portion of the Yucatán Peninsula, hosts a series of elongated depressions trending north/south in the direction of Isla Holbox, identified as the Holbox Fracture Zone. Previous studies have explored the geomorphology and various hydrologic characteristics of the Yucatán Peninsula; however, there is a paucity of data concerning the interior region where the fractures are located. Strontium isotope ratios and major ion geochemistry data of the surface water and groundwater of this region serve as a hydrogeochemical fingerprint, aiding in constraining the hydrological boundaries, determining flow paths, and characterizing hydrogeochemical processes that impact the composition of the groundwater within the region. 87Sr/86Sr isotope ratios indicate a different signature than the surrounding bedrock Sr ratio, suggesting that the flow throughout the Yalahau region is moving through channels faster than that of much of the Yucatán. Through major ion geochemistry and 87Sr/86Sr isotope ratios, we were able to delineate at least two flow paths within the Yalahau region and identify a point of saline intrusion at least 35 km from the coast. Gaining an understanding of the hydrogeochemistry and water flow regions is crucial in determining the impact of various activities (e.g., extensive tourism, drinking water withdrawal, wastewater discharge/injection) that occur within the Yucatán Peninsula.

Poor fisheries data, many fishers, and increasing tourism development: Interdisciplinary views on past and current small-scale fisheries exploitation on Holbox Island

Holbox Island is a contemporary hotspot for global tourism. Here, long-term coastal exploitation and increasing anthropogenic activities threaten coastal habitats and resources. The impact of these activities is exacerbated by the lack of a management plan for the past 24 years, until October 2018. An interdisciplinary approach that integrates fishers’ traditional knowledge was used to determine how small-scale fisheries (SSF) exploitation contributed to the decline of resources over time. Open interviews with community members and surveys of fishers’ perspectives on fisheries overexploitation and practices as well as knowledge of fishing sites were collected. Over one hundred fishing sites were documented that were once very productive. Furthermore, over 40 species were highly fished (e.g., Carcharhinidae, Shpyrnidae, Pristidae, Cheloniidae) over the past 50 years. Survey results allowed for the construction of maps with baseline information of coastal exploitation. Additional data from archaeozoological remains (n= 545) of aquatic fauna identified 33 families of exploited taxa, of which finfish (e.g., Haemulidaea, Ariidae, Serranidae), sharks (e.g., Carcharhinidae), and sea turtles were the most abundant. Fishers and literature sources (n= 50) document Holbox’s contemporary issues, including overfishing, illegal fishing, and accelerated tourism development. These types of data (fishers’ perspectives, interdisciplinary literature, and archaeozoological data) were combined using historical ecology techniques and geospatial tools to obtain novel baseline information on SSF exploitation. This information is essential for conservation managers and scientists to meet the management needs of Holbox’s natural and social capital, which can assure the future provision of coastal ecosystem services to humans.

Water quality of inlets’ water bodies in a growing touristic barrier reef Island “Isla Holbox” at the Yucatan Peninsula

Holbox Island faces issues related to the availability of freshwater and living space given the increasing coastal migration and tourism development in the region. We report the water quality of 12 tidal inlets (which are geomorphological features of barrier islands), which neighbor hotels. Because no previous studies of tidal inlets exist on Holbox, we used reference published values of water quality and unpublished water values collected at 43 sampling sites throughout the Yalahau Lagoon. Analyses of water quality variables and the trophic index (TRIX) were measured. Inlets sites salinity values ranged from 11 to 36 psu. Average values for nitrates (0.83 μmol l−1), and nitrites (0.14 μmol l−1), at inlets, had lower values in the fronts season. Soluble reactive phosphate (48.8μmol l−1), and silicate (78.6 μmol l−1) were higher at inlets during rains and chlorophyll-α (29.7 mg/m3) was more top at inlets during fronts. TRIX values for inlets ranged between 2 and 6, indicating low water quality in most inlets associated with hotel sites. Seasonal changes in soluble reactive phosphate and chlorophyll-α at inlets suggests these could be receiving sewage water discharges from human activities. Besides inlet’s higher water residence time and slower water interchange rate can favor the accumulation of pollutants. Results demonstrate that water quality issues exist on Holbox and need management actions to prevent the decay of coastal ecosystem services. These are necessary for positive feedback between local communities’ wellbeing and successful tourism development in the region.

Metabolismo social y ecoturismo: la problemática de los residuos en isla Holbox, Quintana Roo, México

El modelo de desarrollo imperante que prioriza el crecimiento económico presenta dos límites claros respecto a la naturaleza: los ciclos de recuperación de bienes y servicios y la absorción de los residuos que las actividades humanas generan. La perspectiva del metabolismo social teoriza sobre dichas limitaciones y, como tal, es útil para analizar el problema de los desechos o residuos. Este artículo recupera dicha perspectiva para entender las prácticas de desecho de los mayores generadores de residuos sólidos urbanos en isla Holbox, Q. R., un espacio de reciente promoción turística. A partir de una combinación de métodos cualitativos y cuantitativos que incluyeron encuestas y entrevistas semi-estructuradas, se analizan los requerimientos humanos y materiales involucrados en la transformación espacial que la industria turística promueve, sus consumos y las prácticas de desecho de los residuos sólidos urbanos, así como los conocimientos y percepciones sobre ellos de hoteleros, restauranteros, habitantes, turistas y personas preocupadas por la problemática de la basura. Los resultados muestran la alta dependencia que tiene el ecoturismo de los recursos y reservorios de energía, dependencia manifiesta en la importación de una cantidad y tipo de insumos que complican su eliminación en la isla. Pocos hoteles y restaurantes -y muchos menos habitantes- buscan productos que faciliten la excreción -último proceso del metabolismo social- al tiempo que hay sectores importantes que no están involucrados en prácticas de desecho lo que impide un mejor aprovechamiento de la basura -en un espacio que se complejiza por su dinámica poblacional y socioambiental. Todo lo anterior cuestiona al ecoturismo fomentado por la mercantilización de los espacios pues las prácticas observadas no constituyen alternativas sustentables en términos socioambientales, al considerar casi exclusivamente el factor económico.

A new species of Acanthobothrium (Eucestoda: Onchobothriidae) in Aetobatus cf. narinari (Myliobatidae) from Campeche, México.

The helminthological examination of nine individuals of Aetobatus cf. narinari (spotted eagle ray; raya pinta; arraia pintada) revealed the presence of an undescribed species of cestode of the genus Acanthobothrium. The stingrays were collected from four locations in México: Laguna Términos, south of Isla del Carmen and the marine waters north of Isla del Carmen and Champotón, in the State of Campeche, and Isla Holbox, State of Quintana Roo. The new species, nominated Acanthobothrium marquesi, is a category 3 species (i.e, the strobila is long, has more than 50 proglottids, the numerous testicles greater than 80, and has asymmetrically-lobed ovaries); at the present, the only category 3 species that has been reported in the Western Atlantic Ocean is Acanthobothrium tortum. Acanthobothrium marquesi n. sp. can be distinguished from A. tortum by length (26.1 cm vs. 10.6 cm), greater number of proglottids (1,549 vs. 656), a larger scolex (707 µm long by 872 µm wide vs. 699 µm long by 665 µm wide), larger bothridia (626 µm long by 274 µm wide vs. 563 µm long by 238 µm wide). This is the first report of a species of Acanthobothrium from the Mexican coast of the Gulf México.

Environmental factors influencing aggregation of manta rays (Manta birostris) off the northeastern coast of the Yucatan Peninsula

AbstractManta rays inhabit tropical, subtropical and temperate waters. Aggregation sites of manta rays have been recognized worldwide, but the reasons for this behavior are still poorly understood. This study describes environmental factors influencing aggregation sites of the giant manta ray (Manta birostris) off the northeastern coast of the Yucatan Peninsula. Observations of manta rays were obtained from scientific surveys conducted during 2006–2011. Environmental data were obtained from satellite imagery. The maximum entropy (Maxent) method for habitat modeling was used to determine the effects of environmental conditions on the species and predict suitable habitat for manta rays in this region. Primary productivity and distance to the coast were the most influential variables, suggesting that aggregation occurs in highly productive coastal waters. The distribution of manta rays predicted by the Maxent model showed that the most suitable habitat within the study area is located off the northeastern coast of the Yucatán Peninsula, more precisely, northeast of Isla Holbox and northwest of Isla Contoy. Seasonal patterns of distribution suggest that the most suitable conditions are present from July through September.

A potential third Manta Ray species near the Yucatán Peninsula? Evidence for a recently diverged and novel genetic Manta group from the Gulf of Mexico.

We present genetic and morphometric support for a third, distinct, and recently diverged group of Manta ray that appears resident to the Yucatán coastal waters of the Gulf of Mexico. Individuals of the genus Manta from Isla Holbox are markedly different from the other described manta rays in their morphology, habitat preference, and genetic makeup. Herein referred to as the Yucatán Manta Ray, these individuals form two genetically distinct groups: (1) a group of mtDNA haplotypes divergent (0.78%) from the currently recognized Manta birostris and M. alfredi species, and (2) a group possessing mtDNA haplotypes of M. birostris and highly similar haplotypes. The latter suggests the potential for either introgressive hybridization between Yucatán Manta Rays and M. birostris, or the retention of ancestral M. birostris signatures among Yucatán Manta Rays. Divergence of the genetically distinct Yucatán Manta Ray from M. birostris appears quite recent (<100,000 YBP) following fit to an Isolation-with-Migration model, with additional support for asymmetrical gene flow from M. birostris into the Yucatán Manta Ray. Formal naming of the Yucatán Manta Ray cannot yet be assigned until an in-depth taxonomic study and further confirmation of the genetic identity of existing type specimens has been performed.

Desarrollo sustentable y turismo de naturaleza: reevaluación y acción colectiva en torno a recursos comunes en Holbox, México

The commodification of Holbox Island as a tourism destination has been based on the reassessment of available resources particularly common pool resources. By taking the economic broadly, its necessary to objectify the process of production and reproduction jointly. The creation of value is not only the production of the commodity to be put into circulation, this means to take social reproduction to explain the reconfiguration of economic, social and cultural values. In this regard, production and reproduction leads us to the understanding of the ideological processes that frame the material practices in a particular society. Here, I analyse this articulations to reflect upon the ideological streams that frame local livelihoods and social action under the pressure of wider social fields. In Holbox, the novel values that have been circulating under the frame of ecotourism production are land property and wildlife in the sea; both are generated under the rhythms of the two main markets in the region, viz. nature tourism and real estate. But the creation of tourism commodities led to the dispossession of communal property and the dislocation of the possibilities of exploiting marine wildlife under a common pool resources orientation, due to the messy design and implementation of biodiversity protection policies. Through the empirical traces of this case, I explore how rural societies and their definitions of valuable resources are reconfigured under the pressure and struggles of wider fields of hegemonic domination that use development discourses as an end. This dynamics has important contradictions that make this ideological construct a value to be achieved by rural populations, meanwhile inequalities are reproduced endlessly with the circulation of the idea of “improvement” as a common goal. Keywords: tourism, development, collective action, uneven development.

Participant crowding and physical contact rates of whale shark tours on Isla Holbox, Mexico

Whale shark tourism is a growing niche market within the marine wildlife tourism sector. Increased visitation and declining whale shark numbers at some tourism sites worldwide raise questions over the long-term sustainability of this industry. This study examines the social and potential biological impacts of “swim-with” whale shark tourism on Isla Holbox, Mexico. A total of 397 tour participants completed a self-administered questionnaire regarding perceived crowding, reported encounters and encounter norms, as well as self-reported physical contact rates with whale sharks. Relatively high physical contact rates suggest that tourism may cause some harm to sharks. Users who encountered more swimmers than their norm felt significantly more crowded and were more likely to perceive the industry as having a negative impact on the sharks and surrounding environment. However, the results suggest that the number of boats in the whale shark viewing area may have a greater influence on crowding than number of swimmers. Management interventions to improve the sustainability of the industry include improved interpretation and guide intervention, achieving higher compliance with existing guidelines, and limiting the number of boats allowed in the whale shark viewing area.

Patrones de residencia y movimientos a largo plazo de las toninas Tursiops truncatus, en la región sureste del Golfo de México

Introduction: There are scarce information about the movements and patterns of residence of bottlenose dolphins in the southern part ofthe Gulf of Mexico and the objective of this study is to have information on this subject, Terminos lagoon area is the zone with more effort to study in the region and it is possible that the dolphins move along the coast. Methods: During 1994 to 1999 systematic surveys were carried out to study the movements and residence patterns of bottlenose dolphin populations in four different localities along the coast of the southern Gulf of Mexico, Holbox Island, Quintana Roo, Celestun in Yucatan, Terminos lagoon in Campeche and oriental Tabasco. Results: In total, 2,889 dolphins were photo-identified in the four areas, the majority in the Terminos lagoon (1,987); in this same area one dolphin was recorded within 10 years and nine months, thus having a multi-annual residency pattern. Other dolphin was photo-identified during 1997 in Holbox and 247 days later in Tabasco; another four animals moved from Terminos lagoon to Tabasco, travelling on average 270 km. Discussion and conclusions: These are the first long-term residence patterns and migration records for the species along the southern Gulf of Mexico. Bottlenose dolphins use the coastal lagoons as feeding and shelter areas for calving. The long movements recorded along the Yucatan peninsula between Quintana Roo and Tabasco may evidence a continuous coastal population along the southern Gulf of Mexico. Key words: Bottlenose dolphins; Gulf of Mexico; movements; residence; Tursiops truncatus .

Thermohaline processes in a tropical coastal zone

The detailed thermohaline structure of the northern Yucatan coastal zone was obtained for the first time in order to gain an insight into the interactions between various processes in this complex tropical environment of extreme evaporation and high precipitation rates. From the continent, it has water exchange with numerous coastal lagoons (ranging from brackish to hypersaline) and receives intense submarine groundwater discharges (SGD). In the summer of 2006 a high-resolution (500m cross-shore and 5km along-shore) oceanographic campaign was performed starting at Holbox Island down to the mouth of Celestun Lagoon. CTD profiles were measured at 1020 stations along 69 coastal cross-shore transects. Additionally, CTD data from 2 wider surveys, covering the continental shelf (Campeche Bank) and the southern Gulf of Mexico respectively were used to complement the results. From the thermohaline properties, two main water masses were identified: (a) the Caribbean Subtropical Underwater (CSUW), upwelled from the Caribbean, which was observed at the bottom very close to the coast in more than 260km (from the upwelling region near Cape Catoche to approximately 89.5 W during the summer of 2006) and (b) the second dominant group was a mass of warm hypersaline water which originates in Yucatan due to the high temperature and evaporation rates. We call this water mass the Yucatan Sea Water (YSW) after finding evidence of its presence in various field campaigns both in the Yucatan Sea and further to the west in the southern Gulf of Mexico. All the water masses present in the Yucatan coastal zone showed pronounced variations with important dilution and salinisation effects. The permeable karstic geology of the region prevents the continental water from discharging into the ocean through surface rivers and instead the rainfall permeates directly to the aquifer and travels through caves and fractures towards the sea. Three main regions showed evidence of continental discharges from the coast: the central eastern region (~21.6 N, 87.75 W), around Dzilam Bravo (~21.4 N, 89 W) and, to a lesser degree, the western region of the coast (~21.1 N, 90.3 W). The latter two regions are the eastern and western intersections of the Chicxulub crater ring with the coast respectively.

Horizontal movements, migration patterns, and population structure of whale sharks in the Gulf of Mexico and northwestern Caribbean sea.

Whale sharks, Rhincodon typus, aggregate by the hundreds in a summer feeding area off the northeastern Yucatan Peninsula, Mexico, where the Gulf of Mexico meets the Caribbean Sea. The aggregation remains in the nutrient-rich waters off Isla Holbox, Isla Contoy and Isla Mujeres, Quintana Roo for several months in the summer and then dissipates between August and October. Little has been known about where these sharks come from or migrate to after they disperse. From 2003–2012, we used conventional visual tags, photo-identification, and satellite tags to characterize the basic population structure and large-scale horizontal movements of whale sharks that come to this feeding area off Mexico. The aggregation comprised sharks ranging 2.5–10.0 m in total length and included juveniles, subadults, and adults of both sexes, with a male-biased sex ratio (72%). Individual sharks remained in the area for an estimated mean duration of 24–33 days with maximum residency up to about 6 months as determined by photo-identification. After leaving the feeding area the sharks showed horizontal movements in multiple directions throughout the Gulf of Mexico basin, the northwestern Caribbean Sea, and the Straits of Florida. Returns of individual sharks to the Quintana Roo feeding area in subsequent years were common, with some animals returning for six consecutive years. One female shark with an estimated total length of 7.5 m moved at least 7,213 km in 150 days, traveling through the northern Caribbean Sea and across the equator to the South Atlantic Ocean where her satellite tag popped up near the Mid-Atlantic Ridge. We hypothesize this journey to the open waters of the Mid-Atlantic was for reproductive purposes but alternative explanations are considered. The broad movements of whale sharks across multiple political boundaries corroborates genetics data supporting gene flow between geographically distinct areas and underscores the need for management and conservation strategies for this species on a global scale.

Patterns in composition, abundance and scarring of whale sharks Rhincodon typus near Holbox Island, Mexico

Photo-identification and conventional tagging were used to estimate population size and structure of the whale shark Rhincodon typus near Holbox Island, Mexico. From 2005 to 2008, photographs of spot patterns behind the last gill slit and in a lateral view on the left side of each animal were used to identify individuals. Additionally, 578 R. typus were tagged using conventional marker tags. Of these and the 350 R. typus that were identified from 1184 photographs, 65% were male; 27%, female and 8%, indeterminate sex. Photographed R. typus ranged in size from 2·5 to 9·5 m total length. Size was bimodal with a large peak at 6 m and a smaller peak at 7 m. Photo-identification showed that there was considerable loss of marker tags. Few of these remained on the animals for more than a year, so that interannual re-sights using tagging could not be used in population modelling. Forty six interannual re-sightings were found in the photographic library; the interval between these re-sightings was typically 1 year. It was estimated that the R. typus aggregation near Holbox Island ranged from 521 to 809 individuals, based on mark-recapture models. From 13 to 33% of R. typus photographed had scars that were attributable to boat strikes. This study provides a baseline for assessing the status of R. typus near Holbox Island. This information is useful to understand drivers of local population size and distribution and potential concerns about increasing effects of tourism on R. typus in this area and for designing better management programmes for R. typus conservation.

But are tourists satisfied? Importance-performance analysis of the whale shark tourism industry on Isla Holbox, Mexico

The objective of this paper is to understand the motivations and satisfactions of whale shark tour participants on Isla Holbox, Mexico in order to assess the success of this industry in meeting customer expectations. Whale shark tour participants were provided with a list of environmental and setting features and asked to rate the importance of, and satisfaction with, each feature. Importance-performance (IP) analysis was used to compare these scores and identify areas of management concern. The IP analysis identified key issues with false advertising, lack of educational information, perceived crowding, and tour cost. These factors are representative of larger issues related to the uncontrolled growth of the whale shark tourism industry on Holbox. Management should focus on limiting the growth of the industry, ensuring the equitable distribution of economic benefits within the industry, and developing and implementing effective guide training and interpretation programs.

An Unprecedented Aggregation of Whale Sharks, Rhincodon typus, in Mexican Coastal Waters of the Caribbean Sea

Whale sharks, Rhincodon typus, are often perceived as solitary behemoths that live and feed in the open ocean. To the contrary, evidence is accumulating that they are gregarious and form seasonal aggregations in some coastal waters. One such aggregation occurs annually north of Cabo Catoche, off Isla Holbox on the Yucatán Peninsula of Mexico. Here we report a second, much denser aggregation of whale sharks (dubbed “the Afuera”) that occurs east of the tip of the Yucatán Peninsula in the Caribbean Sea. The 2009 Afuera event comprised the largest aggregation of whale sharks ever reported, with up to 420 whale sharks observed in a single aerial survey, all gathered in an elliptical patch of ocean approximately 18 km2. Plankton studies indicated that the sharks were feeding on dense homogenous patches of fish eggs, which DNA barcoding analysis identified as belonging to little tunny, Euthynnus alletteratus. This contrasts with the annual Cabo Catoche aggregation nearby, where prey consists mostly of copepods and sergestid shrimp. Increased sightings at the Afuera coincide with decreased sightings at Cabo Catoche, and both groups have the same sex ratio, implying that the same animals are likely involved in both aggregations; tagging data support this idea. With two whale shark aggregation areas, high coastal productivity and a previously-unknown scombrid spawning ground, the northeastern Yucatán marine region is a critical habitat that deserves more concerted conservation efforts.

Isolation and characterization of microsatellite loci in the whale shark (Rhincodon typus)

In preparation for a study on population structure of the whale shark (Rhincodon typus), nine species-specific polymorphic microsatellite DNA markers were developed. An initial screening of 50 individuals from Holbox Island, Mexico found all nine loci to be polymorphic, with two to 17 alleles observed per locus. Observed and expected heterozygosity per locus ranged from 0.200 to 0.826 and from 0.213 to 0.857, respectively. Neither statistically significant deviations from Hardy-Weinberg expectations nor statistically significant linkage disequilibrium between loci were observed. These microsatellite loci appear suitable for examining population structure, kinship assessment and other applications.