Spatial and temporal variability of immature green turtle abundance and somatic growth in Puerto Rico

Abstract

Understanding conservation needs relies on robust estimates of key population parameters, such as survival, abundance and somatic growth. We investigated the somatic growth and abundance dynamics of 2 aggregations of immature green turtles, at Tortuga Bay and Puerto Manglar (Culebra, Puerto Rico), throughout 15 yr of capture-mark-recaptures. We used nonlinear models to investigate the effects of carapace length, sampling year, growth interval and the presence of fibropapillomas on growth rates, and used the size-specific growth rate function to estimate how long turtles remain at each bay. Abundances were estimated and compared with timespecific growth rate functions, to infer density-dependency effects on somatic growth rates, and trends in abundance were evaluated by fitting generalized linear models. We found foraging site specific growth rates and report the highest mean somatic growth rate for green turtles in the wild (6.1 ± 1.7 cm yr −1 , at Puerto Manglar). The size-specific growth rate function was monotonic at both sites, with growth rates declining continuously with increasing carapace length. We inferred minimum ages at maturity of 14 and 22 yr, for Puerto Manglar and Tortuga Bay turtles, respectively. Throughout the 15 yr of this study there was a positive trend in aggregation size at Puerto Manglar (mean annual increase of 10.9%), which was not observed at Tortuga Bay. Our study highlights the influence of geography and habitat quality on somatic growth rates, and delivers robust demographic estimates valuable for local and regional assessments of the conservation status of the green turtle.

Movement patterns of juvenile hawksbill turtles Eretmochelys imbricata at a Caribbean coral atoll: long-term tracking using passive acoustic telemetry

“…While our study has provided valuable data regarding the movements of juvenile hawksbill turtles around an offshore developmental habitat, other methods of long-term monitoring, such as satellite telemetry and stable isotope analysis, would permit insights even if tracked individuals were to leave the atoll (Shimada et al 2014). Technological advances aside, with suffi-cient commitment of time and resources, there is also much still to be gained from traditional capturemark-recapture methods (Patrício et al 2014). What will ultimately enable a more complete understanding of the niche that hawksbills fill within reef ecosystems is an integrative approach, in which multiple methods, populations, and locations are used to fill the gaps in ecology (Hart & Hyrenbach 2009, Godley et al 2010, Scales et al 2011).…”

Genetic composition and origin of juvenile green turtles foraging at Culebra, Puerto Rico, as revealed by mtDNA

“…comm.). At Puerto Manglar, a positive trend on abundance with a mean annual increase of 10.9% was observed over the course of 15 years ( , Patrício et al, 2014, more accentuated from 2006, owing to increased recruitment. This reflects the positive trend in the source populations (Chaloupka et al, 2008), which may lead to changes in the relative contributions from Atlantic rookeries to the Culebra aggregation, particularly if they are not all recover at the same pace.…”

“…A longterm capture-mark-recapture (CMR) program has revealed that immature turtles remain in these bays for several years (ca. 10 to 17 years, Patrício et al, 2014), and that larger immature turtles (>65 cm SCL) permanently emigrate, potentially to subadult foraging sites closer to their breeding grounds (Patrício et al, 2011). As turtles spend such a long period of their early life at these developmental sites, mortality there can impact the multiple rookeries to which they are linked.…”

“…In Puerto Rico, Puerto Manglar and Tortuga Bay at Culebra, are recognized as important developmental habitats for juvenile green turtles (Diez et al, 2010;Patrício et al, 2011Patrício et al, , 2014. Turtles as small as 23 cm SCL are known to recruit into these coastal bays, where they spend over a decade, departing before the onset of sexual maturity (Patrício et al, 2011(Patrício et al, , 2014.…”

“…Turtles as small as 23 cm SCL are known to recruit into these coastal bays, where they spend over a decade, departing before the onset of sexual maturity (Patrício et al, 2011(Patrício et al, , 2014. Here we investigate the genetic composition of these foraging aggregations during a period of seven years and estimate the most likely origins of these stocks using a MSA, including 14 Atlantic nesting populations as potential sources.…”