Long-term growth and survival dynamics of green turtles (Chelonia mydas) at an isolated tropical archipelago in Brazil

Knowledge of life history parameters is essential for the effective management of species of conservation concern. For migratory marine vertebrates such as hawksbill sea turtles Eretmochelys imbricata, feeding aggregations are important developmental habitats, allowing the study of population dynamics. Here, we used data from a 31 yr mark-recapture study of juvenile hawksbill sea turtles in the Fernando de Noronha Archipelago, Brazil, to estimate key demographic parameters. Turtles recruit to the neritic habitat at similar sizes to those of other Atlantic hawksbill aggregations. The curved carapace length (CCL) at the first capture ranged from 28 to 84 cm (mean ± SD: 44.6 ± 9.8 cm). Median minimum residence time of turtles captured at least twice was 3.2 yr, whilst long-term minimum residence of up to 14 yr was also observed, with turtles showing site fidelity within the archipelago. The mean size of turtles captured was constant throughout time. Turtles grew on average 3.4 ± 2.2 cm yr-1 , with a monotonic expected growth rate function generally decreasing with increasing size. At these rates, hawksbill turtles in Fernando de Noronha would need to spend ca. 14−18 yr to reach minimum adult breeding size (~74 cm CCL). This mark-recapture study has been essential to understanding the ecology and demographic parameters of this regional hawksbill turtle neritic foraging ground.

Section: Temporal Patterns and Field Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Distribution and growth rates of immature hawksbill turtles Eretmochelys imbricata in Fernando de Noronha, Brazil

Bellini¹,

Santos²,

Patrício³

et al. 2019

“…Recently, important efforts have been made to estimate population abundance and survival of green turtles based on long-term population monitoring using mark-recapture methods of nesting females (Balazs & Chaloupka 2004, Troëng & Rankin 2005, Koch et al 2007, Troëng & Chaloupka 2007 in foraging aggregations (Chaloupka & Limpus 2001, Bjorndal et al 2003, 2005b, Seminoff et al 2003, Campbell & Lagueux 2005, Patrício et al 2011, Colman et al 2015 and remote tracking of individuals using satellite telemetry (Pelletier et al 2003). However, a large variation has been observed among species, regions, and even populations (Casa le et al 2007, Troëng & Chaloupka 2007.…”

Section: Introductionmentioning

confidence: 99%

Population trends and survival of nesting green sea turtles Chelonia mydas on Aves Island, Venezuela

Garcia-Cruz¹,

Lampo²,

Peñaloza³

et al. 2015

Long-term demographic data are valuable for assessing the effect of anthropogenic impacts on endangered species and evaluating recovery programs. Using a 2-state open robust design model, we analyzed mark-recapture data from green turtles Chelonia mydas sighted between 1979 and 2009 on Aves Island, Venezuela, a rookery heavily impacted by human activities before it was declared a wildlife refuge in 1972. Based on the encounter histories of 7689 nesting females, we estimated the abundance, annual survival, and remigration intervals for this population. Female survival varied from 0.14−0.91, with a mean of 0.79, which is low compared to survival of other populations from the Caribbean (mean = 0.84) and Australia (mean = 0.95), even though we partially corrected for tag loss, which is known to negatively bias survival estimates. This supports prior suggestions that Caribbean populations in general, and the Aves Island population in particular, may be more strongly impacted than populations elsewhere. It is likely that nesters from this rookery are extracted while foraging in remote feeding grounds where hunting still occurs. Despite its relatively low survival, the nesting population at Aves Island increased during the past 30 years from approx. 500 to >1000 nesting females in 2009. Thus, this population, like others in the Caribbean and the Atlantic, seems to be slowly recovering following protective management. Although these findings support the importance of long-term conservation programs aimed at protecting nesting grounds, they also highlight the need to extend management actions to foraging grounds where human activities may still impact green turtle populations.

“…While studies on these aspects of turtle biology are generally on the rise (e.g. Avens et al 2013, Lopez-Castro et al 2013, Casale et al 2014, Patricio et al 2014, Colman et al 2015, there is no information on Arabian Gulf sea turtle sex ratios in development and foraging grounds or on age-class structure; nor are there any descriptions of non-adult components of the populations. These data are important for understanding the status and survival of turtle populations during earlier life stages (NRC 2010) and for the development of appropriate conservation strategies which target all life stages of marine turtles.…”

Section: Introductionmentioning

confidence: 99%

Population structure of marine turtles in coastal waters of Qatar

Pilcher¹,

Al-Maslamani²,

Williams³

et al. 2015

Knowledge of the interrelationships between habitats and life-stage development in marine turtles requires an understanding of recruitment, size and age at maturity, sex ratios, growth and sexual development rates, survivorship and nesting probabilities. These data may be used to determine the status and survival of turtle populations during earlier life stages and for the development of appropriate conservation strategies. We sampled in-water stocks of marine turtles in coastal waters of Qatar using rodeo-style captures, entrapments in an industrial cooling intake and opportunistic bycatch to determine species, size, gender and age class. Our results revealed that Qatar is home to a resident population of small juvenile green turtles (< 40 cm curved carapace length, CCL) and a transient population of juvenile hawksbills (< 25 cm CCL) at an approximate 7:3 ratio of green to hawksbill turtles. Hawksbills were male-biased (4M:1F) while green turtles were slightly female biased (2M:3F). Given the extreme high ambient and water temperatures in the Arabian Gulf, which may be considered a living laboratory for understanding climate change effects on marine species, our results are not conclusive that elevated temperatures have led to feminisation of marine turtle populations. We instead believe that there may be a regional and/or evolutionary shift in the pivotal temperature that regulates ecologically appropriate sex determination, which requires further investigation. Our data provide, for the first time, a description of the foraging marine turtle population structure in Qatari waters, and point to a need for protection of seagrass beds, effective mitigation measures for sedimentation from coastal development and rehabilitation of coral-reef habitats.