Trophic ecology of juvenile bull sharks (Carcharhinus leucas) in the Coyote estuary, Costa Rica.

Bull shark (Carcharhinus leucas) is a near-threatened elasmobranch species capable of moving between the fresh and salty waters of tropical and subtropical coastal areas, for which we still lack important ecological information. During their first years of life, bull sharks use estuarine systems as nursery areas, making them highly susceptible to environmental and anthropogenic pressures. We studied the trophic ecology of juveniles found in the Coyote estuary, a potential nursery area in Costa Rica, to understand the potential impact of further bull shark declines and gain knowledge that could aid in their conservation. We analysed the trophic ecology of juvenile bull sharks [81-103 cm total length (TL)] in the Coyote estuary, Costa Rica, using stable isotopes of δ15 N and δ13 C. Since one problem using this technique in juveniles is the confounding effect of the maternal signature, we sampled different tissues (muscle and plasma), verified the status of the shark's umbilical scar and identified the size at which the isotope signature is a result of the animal's current diet. The isotopic values of the muscle tissue reflected the maternal isotopic signature. In contrast, plasma values reflected the diet of juvenile bull sharks >95 cm TL and with a closed umbilical scar. Juvenile bull sharks fed primarily on teleost fishes of the order Anguilliformes and Siluriformes, and have a high trophic position (≥4.0) in the Coyote estuary. Our findings suggest that this estuary is an important feeding site for juvenile bull sharks of the Pacific of Costa Rica. Thus, the protection of essential habitats such as the Coyote estuary will benefit not only bull shark conservation, but also the conservation of an array of fish species that also use this habitat as a rookery, many of which are of commercial interest.

Population structure and genetic connectivity of the scalloped hammerhead shark (Sphyrna lewini) across nursery grounds from the Eastern Tropical Pacific: Implications for management and conservation.

Defining demographically independent units and understanding patterns of gene flow between them is essential for managing and conserving exploited populations. The critically endangered scalloped hammerhead shark, Sphyrna lewini, is a coastal semi-oceanic species found worldwide in tropical and subtropical waters. Pregnant females give birth in shallow coastal estuarine habitats that serve as nursery grounds for neonates and small juveniles, whereas adults move offshore and become highly migratory. We evaluated the population structure and connectivity of S. lewini in coastal areas and one oceanic island (Cocos Island) across the Eastern Tropical Pacific (ETP) using both sequences of the mitochondrial DNA control region (mtCR) and 9 nuclear-encoded microsatellite loci. The mtCR defined two genetically discrete groups: one in the Mexican Pacific and another one in the central-southern Eastern Tropical Pacific (Guatemala, Costa Rica, Panama, and Colombia). Overall, the mtCR data showed low levels of haplotype diversity ranging from 0.000 to 0.608, while nucleotide diversity ranged from 0.000 to 0.0015. More fine-grade population structure was detected using microsatellite loci where Guatemala, Costa Rica, and Panama differed significantly. Relatedness analysis revealed that individuals within nursery areas were more closely related than expected by chance, suggesting that S. lewini may exhibit reproductive philopatric behaviour within the ETP. Findings of at least two different management units, and evidence of philopatric behaviour call for intensive conservation actions for this highly threatened species in the ETP.

Asociación de tiburones con el Monte Submarino Las Gemelas y primera evidencia de conectividad con la Isla del Coco, Pacífico de Costa Rica

Introducción: Los montes submarinos y las islas oceánicas son conocidos como "puntos calientes" de biodiversidad pelágica, los cuales son utilizados por especies altamente migratorias como corredores biológicos naturales. En el Pacífico Tropical Oriental se han establecido una serie de Áreas Marinas Protegidas (AMPs) cuyo objetivo principal es proteger y manejar los recursos marinos que se encuentran dentro de esta región. Sin embargo, muchas de estas AMPs no incluyen esquemas de protección absoluta, y ninguna cuenta con la capacidad de de proteger a las especies altamente móviles una vez que estas se desplazan fuera de sus límites. Objetivos: El objetivo del presente estudio es dar a conocer la primer evidencia de conectividad entre el Parque Nacional Isla del Coco (PNIC) y el monte submarino Las Gemelas ubicado dentro del Área Marina de Manejo Montes Submarinos (AMM-MS) registrada por un tiburón martillo hembra (Sphyrna lewini). Métodos: Entre mayo del 2015 y mayo del 2016 un tiburón martillo y un tiburón zorro (Alopias pelagicus) fueron marcados (V16, Vemco Ltd.) y monitoreados por una serie de receptores acústicos ubicados en el PNIC y en Las Gemelas. Los datos fueron analizados descriptivamente y se calculó el índice de residencia (IR). Resultados: S. lewini realizó viajes de ida y vuelta entre los sitios ubicados dentro del PNIC y el AMM-MS. El mayor número de detecciones registradas por S. lewini ocurrieron en Roca Sucia, y todas las detecciones tuvieron lugar durante las horas de la mañana (7:00 - 12:00 h). S. lewini exhibió una baja residencia (IR=0.02) y una presencia periódica en el área de estudio. Se detectó la presencia de A. pelagicus en Las Gemelas casi un año después de haber sido marcado en ese mismo lugar. Conclusiones: La presencia periódica de S. lewini entre estas dos AMPs, y la presencia de A. pelagicus en Las Gemelas sugiere que los movimientos entre las islas oceánicas de la región puede ser más complejo que simples movimientos de "ida y vuelta", donde los montes submarinos juegan un papel importante en el desplazamiento de dichas especies. Nuestros resultados destacan la importancia de aumentar la protección a los montes submarinos y de crear corredores marinos que conecten las islas oceánicas con el fin de promover la conservación de especies altamente migratorias. Aunque la creación de AMPs alrededor de estas formaciones geológicas se ha propuesto como una manera efectiva de conservar y proteger la biodiversidad marina en aguas abiertas, su efectividad es solo parcial. Esta investigación resalta la importancia de estudiar la dinámica espacial de especies altamente migratorias con el objetivo de mejorar el diseño y la efectividad de AMPs ubicadas lejos del continente como es el caso del PNIC y el AMM-MS.

Introduction: Seamounts and oceanic islands are known as hotspots of pelagic biodiversity, which highly migratory species use as natural biological corridors. Although marine protected areas have been established in the Eastern Tropical Pacific with a goal to protect and manage region's marine biodiversity, not all utilize or enforce a no-take policy, and none are capable of protecting highly mobile species once they move outside of the limit of these areas. Objective: We present the first evidence of shark connectivity between Cocos Island National Park (CINP) and Las Gemelas seamount located in the Seamounts Marine Management Area (SMMA), by a female scalloped hammerhead shark (Sphyrna lewini). Methods: Between May 2015 and May 2016 a scalloped hammerhead shark and a pelagic thresher shark (Alopias pelagicus) were tagged (V16, Vemco Ltd.) and monitored by an array of acoustic receivers installed at CINP and Las Gemelas. We analyzed the acoustic data descriptively and we calculated the residency index (IR). Results: S. lewini performed persistent movements between these two marine protected areas. All detections in Cocos Island occurred during the morning (7:00-12:00 h) and Roca Sucia was the most visited site. The shark shows a low residency (IR=0.02) and intermittent presence in the study area. We recorded the presence of A. pelagicus at Las Gemelas almost one year after it was tagged at the site. Conclusions: The persistent movements of S. lewini between these two pelagic marine protected areas, and the presence of a tagged A. pelagicus at Las Gemelas seamount, suggests that movements between oceanic islands in the region may be more complex than simple "back and forth" movements, with seamounts in between them acting as stepping stones, where they may also stay for periods of time. Our results emphasize the importance of granting greater protection to seamounts and creating connecting swimways to oceanic island hotspots for the conservation of pelagic and highly migratory species. Although the establishment of marine reserves around oceanic islands and seamounts have been proposed as an effective way to conserve and protect marine biodiversity in the high seas, their effectiveness is only partial. This study highlights the importance of studying the spatial dynamics of highly migratory species to help improve the design and efficiency of marine protected areas located in the high seas such as CINP and SMMA.

Time partitioning among jaguar Panthera onca, puma Puma concolor and ocelot Leopardus pardalis (Carnivora: Felidae) in Costa Rica's dry and rainforests / Separación temporal del jaguar Panthera onca, puma Puma concolor y ocelote Leopardus pardalis (Carnivora: Felidae) en los bosques tropicales húmedos y secos de Costa Rica

Abstract Segregation of daily activity patterns is considered an important mechanism facilitating the coexistance of competing species. Here, we evaluated if temporal separation existed among jaguar (Panthera onca), puma (Puma concolor) and ocelot (Leopardus pardalis) and if their activity patterns were related to that of a particular prey. We used camera trap records to estimate the activity schedules of these predators and their prey. We used the coefficient of overlapping (Δ; ranging from 0 to 1) to quantify the temporal interactions between predators and prey, and calculated confidence intervals from bootstrap samples. Strong temporal overlap occurred among the three felids (Δ = 0.63 - 0.82) in both dry and rainforests. However, a greater temporal separation was observed between the closest competitors (jaguar and puma, puma and ocelot). Jaguar and puma had a strong temporal overlap with medium and large-sized prey, while ocelots' activity matched that of smallsized prey. High overlapping coefficients among the felids suggest that temporal segregation is not the main mechanism facilitating their coexistence in these areas. However, fine-scale or spatiotemporal differences in their activity patterns might contribute to their coexistence in tropical environments.(AU)

Resumen La segregación de los patrones de actividad diaria es considerado un importante mecanismo para la coexistencia de especies competidoras. En este estudio, evaluamos si existía separación temporal entre el jaguar (Panthera onca), puma (Puma concolor) y ocelote (Leopardus pardalis), y si sus patrones de actividad se relacionaban con los de sus presas potenciales. Utilizamos registros de cámaras trampa para estimar los patrones de actividad de los felinos y sus presas. Usamos el coeficiente de traslape (Δ; de 0 a 1) para cuantificar las interacciones temporales entre depredadores y presas y calculamos los intervalos de confianza mediante bootstrapping. Observamos un fuerte traslape temporal (Δ= 0.63-0.82) entre los felinos tanto en el bosque seco como en el lluvioso. La mayor segregación temporal ocurrió entre los competidores más cercanos (jaguar y puma, puma y ocelote). El jaguar y el puma tuvieron un fuerte traslape con las presas medianas y grandes, mientras que el ocelote se traslapó con presas más pequeñas. Los altos coeficientes de traslape entre los felinos sugieren que la segregación temporal no es el mecanismo principal de coexistencia en estos sitios. Sin embargo, pequeñas diferencias en los patrones de actividad (e.g. picos de actividad desfasados) podrían contribuir a su coexistencia en ambientes tropicales.(AU)