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Antecedentes y Objetivos: La restauración ecológica se ha centrado en los componentes físicos y vegetales de los ecosistemas, y ha dejado de lado a la fauna silvestre y sus interacciones. Chelonia mydas es un macroherbívoro en peligro de extinción que anida en playas de México y Cuba, e influye en la vegetación costera con aportaciones de materia orgánica. Los objetivos de este estudio fueron analizar su recuperación poblacional, un índice del verdor de la vegetación de duna, así como la cantidad de materia orgánica estimada de sus nidadas antes y después de la implementación de una Norma Oficial Mexicana. Métodos: Se analizaron datos de entre dos y tres décadas de monitoreo biológico en 16 playas de anidación de Chelonia mydas; a partir de ellos se realizaron tres niveles de análisis de indicadores demográficos, la aportación de materia orgánica de las tortugas en la playa y el vigor vegetal a partir de sensores remotos, además de aplicar los estadísticos pertinentes. Resultados clave: Hubo un crecimiento exponencial del número de anidaciones de tortuga verde (entre 12 y 14% anual), asociado con pulsos de reclutamiento poblacional en los años 2000 y 2008. El aporte de materia orgánica a la playa fue significativamente mayor después de un cambio en la estrategia para manejo de las nidadas en México, y se detectó un incremento en el verdor de la vegetación de duna en zonas de anidación alta de Chelonia mydas. Conclusiones: El incremento de las poblaciones de tortuga verde lleva a reflexionar acerca de las implicaciones que tiene la recuperación de especies de fauna sobre otras comunidades en los ecosistemas que habitan, lo que demanda el análisis de los paradigmas actuales y la adaptación de estrategias que atiendan sus necesidades de manejo, procurando las condiciones de integridad ecológica de sus hábitats.

International audience; Oceanic dispersal characterizes the early juvenile life‐stages of numerous marine species of conservation concern. This early stage may be a ‘critical period’ for many species, playing an overriding role in population dynamics. Often, relatively little information is available on their distribution during this period, limiting the effectiveness of efforts to understand environmental and anthropogenic impacts on these species. Here we present a simple model to predict annual variation in the distribution and abundance of oceanic‐stage juvenile sea turtles based on species’ reproductive output, movement and mortality. We simulated dispersal of 25 cohorts (1993–2017) of oceanic‐stage juveniles by tracking the movements of virtual hatchling sea turtles released in a hindcast ocean circulation model. We then used estimates of annual hatchling production from Kemp's ridley Lepidochelys kempii (n = 3), green Chelonia mydas (n = 8) and loggerhead Caretta caretta (n = 5) nesting areas in the northwestern Atlantic (inclusive of the Gulf of Mexico, Caribbean Sea and eastern seaboard of the U.S.) and their stage‐specific mortality rates to weight dispersal predictions. The model's predictions indicate spatial heterogeneity in turtle distribution across their marine range, identify locations of increasing turtle abundance (notably along the U.S. coast), and provide valuable context for temporal variation in the stranding of young sea turtles across the Gulf of Mexico. Further effort to collect demographic, distribution and behavioral data that refine, complement and extend the utility of this modeling approach for sea turtles and other dispersive marine taxa is warranted. Finally, generating these spatially‐explicit predictions of turtle abundance required extensive international collaboration among scientists; our findings indicate that continued conservation of these sea turtle populations and the management of the numerous anthropogenic activities that operate in the northwestern Atlantic Ocean will require similar international coordination.

The Deepwater Horizon explosion in April 2010 and subsequent oil spill released 3.19 × 106 barrels (5.07 × 108 l) of MC252 crude oil into important foraging areas of the endangered Kemp’s ridley sea turtle Lepidochelys kempii (Lk) in the northern Gulf of Mexico (GoM). We measured δ13C and δ15N in scute biopsy samples from 33 Lk nesting in Texas during the period 2010 to 2012. Of these, 27 were equipped with satellite transmitters and were tracked to traditional foraging areas in the northern GoM after the spill. Differences in δ13C between the oldest and newest scute layers from 2010 nesters were not significant, but δ13C in the newest layers from 2011 and 2012 nesters was significantly lower compared to 2010. δ15N differences were not statistically significant. Collectively, the stable isotope and tracking data indicate that the lower δ13C values reflect the incorporation of oil rather than changes in diet or foraging area. Discriminant analysis indicated that 51.5% of the turtles sampled had isotope signatures indicating oil exposure. Growth of the Lk population slowed in the years following the spill. The involvement of oil exposure in recent population trends is unknown, but long-term effects may not be evident for many years. Our results indicate that C isotope signatures in scutes may be useful biomarkers of sea turtle exposure to oil.

Many species of marine organisms go through ontogenetic shifts that occur in unknown or inaccessible locations. Finding these areas is crucial to understand con- nectivity and resilience of populations, both of which have conservation implications. When extrinsic markers are not suitable to track organisms, intrinsic markers can be use- ful to infer the location of inaccessible areas where these cryptic stages occur. Our study focuses on the location of oceanic foraging areas of the cryptic early juvenile stage of green turtles, Chelonia mydas, in the Atlantic. Due to the small size of hatchlings, the use of telemetry is limited to short periods of time and small spatial ranges, which do not allow determining the location of oceanic foraging areas. We used lead (Pb) stable isotopes to determine the possible location of oceanic foraging areas of small green turtles in the Atlantic Ocean. Pb stable isotope ratios in the scute tis- sue deposited when turtles were in the oceanic habitat were compared to ratios of major sources of lead in the Atlantic and oceanic areas in the Atlantic to determine the location of oceanic foraging grounds. The Pb isotope ratios in the scute of oceanic-stage green turtles indicated that turtles

Use of scute in biochemical studies to infer ontogenetic changes of habitat and diet in sea turtles is becoming more frequent because scute is an inert tissue with continuous growth that can record habitat and diet changes through time. Changes are detectable through biochem- ical markers such as stable isotopes and trace elements. These studies are critical for the manage- ment of endangered sea turtles because location and foraging requirements of these animals must be known in order to be able to provide effective protection measures. However, scute thickness is not homogeneous throughout the carapace. Depending on where in the scute a sample is col- lected, a different version of the history of an individual turtle could be obtained. Our goal was to determine where on the carapace the thickest scute is found in green turtles Chelonia mydas and loggerhead turtles Caretta caretta and whether this area reveals the longest life history of the tur- tle based on stable isotopes of carbon and nitrogen. Our results show that regardless of size, the thickest part of the scute is found in the central region of the second lateral scute in green turtles and of the third lateral scute in loggerheads. Furthermore, the thickest areas do provide the longest records of the history of green turtles and, perhaps, of loggerhead turtles. We were able to observe a clear shift of habitat from the stable isotope values in the central region of the scute of several green turtles that was not observed in the posterior margin. Thus, the central region site should be used to collect scute tissue as this provides information on the life history of sea turtles over the longest period of time.

Assessing population structure and connectivity of species that have cryptic life stages, such as sea turtles, is a challenge in conservation biology. The early oceanic stage of sea turtles, also known as the 'lost years', is poorly known. Green turtle Chelonia mydas hatchlings emerge from their nests, enter the sea, and inhabit oceanic (open ocean) habitats where they are rarely seen until they recruit to coastal (neritic) foraging grounds several years later. Therefore, the location of and population structure in oceanic foraging grounds, as well as the connections between oceanic and neritic foraging grounds, are difficult to determine. Given that long-term tracking devices are not available for sea turtle hatchlings, the use of other markers, such as trace elements and stable isotopes, is necessary to study the oceanic stages of sea turtles. We analyzed the elemental composition and ratios of stable isotopes of carbon and nitrogen of scute tissue that was deposited when turtles were in the oceanic habitat to characterize 6 oceanic foraging areas used by green turtles in the Atlantic Ocean. We determined that there is significant structuring among oceanic green turtle aggregations and multiple links between oceanic and neritic foraging areas. We discuss the conservation implications of structured oceanic aggregations with multiple links, as well as the use of trace elements (particularly titanium, chromium, zirconium and barium) in the characterization of oceanic regions.

The green sea turtle (also known locally as black turtle; Chelonia mydas) is 1 of 5 species of sea turtles found along the coast of the state of Baja California Sur, Mexico, where several bays and lagoon systems provide an important growth and feeding habitat. We characterized blood biochemistry values of 67 green turtles captured at 2 mangrove estuaries along the Pacific coast of the Baja California Peninsula, Mexico, from 2005 to 2007. Blood samples were collected from live turtles for biochemical analysis of 18 parameters and analyzed by physical state (healthy, injured), size classes, season, and geographic location. Green turtles showed differences in the variability of the biochemical parameters between the 2 sites. In Punta Abreojos, injured sea turtles had lower calcium (28%), potassium (28%), and inorganic phosphorus (34.5%) levels and higher cholinesterase activity (16%) compared to healthy turtles. Juvenile turtles collected in Bahia Magdalena had higher glucose levels (34%) than subad...

Monthly in-water monitoring was conducted at 5 foraging areas off the Baja California Peninsula, Mexico, from 2001 to 2006 to assess black turtle population status. Turtles were captured with entanglement nets, size (straight carapace length, SCL) and weight of each individual were recorded and turtles were tagged on both rear flippers. A total of 1238 turtles were captured, involv- ing 6309 h of effort. Of this total, 937 ind. were marked and 155 were recaptured. SCL ranged from 30 to 95.5 cm; immature turtles accounted for >94% of the total catch and were dominant at all sites. However, size class distribution varied among sites, and turtles from the Gulf of California were sig- nificantly larger than those caught in the Pacific. Catch per unit of effort (defined as the number of turtles caught per 100 m of net soaking for 24 h) varied from 1.79 at Bahia Magdalena to 17.35 at Punta Abreojos. Mean (±SD) annual growth rate for black turtles was 2.27 ± 0.71 cm yr -1 , with the lowest and highest growth rates in Bahia Magdalena (1.37 ± 0.71 cm yr -1 ) and Laguna Ojo de Liebre (3.05 ± 2.23 cm yr -1 ), respectively. Lack of recaptures from adjacent sites and multiple recaptures of specimens at the site of origin over several years indicate a low connectivity among foraging areas and a high site fidelity. Hence, strengthening local protection is imperative to the recovery of black sea turtle populations.

Since 2001, Grupo Tortuguero has been conducting monthly in-water monitoring of East Pacific green turtles (Chelonia mydas), also known as black turtles, at four neritic foraging areas (Bahia Magdalena, Laguna San Ignacio, Punta Abreojos, Laguna Ojo de Liebre) along the Pacific coast of Baja California Sur, Mexico. Extensive tagging (883 turtles tagged of 1,183 turtles captured) and recaptures (154 tagged turtles recaptured at least once) at these four areas suggest that immature East Pacific green turtles show strong site fidelity to their neritic foraging grounds. However, in 2007, we recaptured two immature turtles, one in Laguna San Ignacio and the other in Bahia Magdalena, that were both originally captured in Punta Abreojos. To our knowledge, this represents the first direct evidence of immature East Pacific green turtles using multiple foraging areas along the Baja California Peninsula. This report highlights the importance of long-term monitoring efforts that encompass several habitats on a relatively large spatial scale (~80 km between Punta Abreojos and Laguna San Ignacio and ~300 km between Punta Abreojos and Bahia Magdalena) to better understand the movements and habitat use of immature East Pacific green turtles on their neritic foraging areas.

Previous studies of the olive ridley Lepidochelys olivacea population structure in the tropical eastern Pacific have indicated the existence of a single panmictic population ranging from Costa Rica to Mexico. This information has been used to design specific management measures to conserve primary nesting beaches in Mexico. However, little is known about olive ridleys in the Baja California Peninsula, their northernmost reproductive limit, where recent observations have shown differences in nesting female behaviour and size of hatchlings relative to other continental rookeries. We used mtDNA control region sequences from 137 turtles from five continental and four peninsular nesting sites to determine whether such differences correspond to a genetic distinction of Baja California olive ridleys or to phenotypic plasticity associated with the extreme environmental nesting conditions of this region. We found that genetic diversity in peninsular turtles was significantly lower than in continental nesting colonies. Analysis of molecular variance revealed a significant population structure (Φ Φ Φ ST = 0.048, P = 0.006) with the inclusion of peninsular samples. Our results: (i) suggest that the observed phenotypic variation may be associated with genetic differentiation and reproductive isolation; (ii) support the recent colonization of the eastern Pacific by Lepidochelys ; ( iii) reveal genetic signatures of historical expansion and colonization events; and (iv) significantly challenge the notion of a single genetic and conservation unit of olive ridleys in the eastern Pacific. We conclude that conservation measures for olive ridleys in Mexico should be revised to grant peninsular beaches special attention.

Baja California represents the northernmost reproductive area for Lepidochelys olivacea. This region is characterized by its high temperature and low humidity. Thus, nest site selection plays an important role in reproductive success. To evaluate the factors affecting site selection for oviposition Las Barracas Beach, located in the south of the peninsula, was visited, from August to November 2000, in weekly periods. A density of 2.55 nests ha−1 was estimated from a total of 55 nests counted. A hatching success of 73.7% was observed, with 23.7% mortality and 2.5% of eggs without apparent development (eggs counted=4,031). On the day of oviposition, the relative surface humidity (between 0.75% and 1.75%) and temperature (32°C) preferred by the females for nest construction was determined at the nest site, as well as the mean distance between the nests and the high tide line for that day (17.65 m). Hatching success was affected by humidity and distance. In addition, hatching success was higher between 10 and 30 m above the high tide line measured on the day of oviposition (surface humidity ca. 1%). A total of 874 hatchlings were measured, with an average of 42.1 mm straight carapace length. Larger sizes were found in October and smaller ones in November. Generally speaking, the sizes found here were larger than those obtained in other areas. This is probably due to two factors: (1) the nests in Las Barracas were kept in situ, whereas in other areas nests are sometimes incubated artificially and (2) the nesting population of southern Baja California is different from the eastern Pacific population.