Somatic growth dynamics are an integrated response to environmental conditions. Hawksbill sea turtles (Eretmochelys imbricata) are long-lived, major consumers in coral reef habitats that move over broad geographic areas (hundreds to thousands of kilometers). We evaluated spatio-temporal e ects on hawksbill growth dynamics over a 33-yr period and 24 study sites throughout the West Atlantic and ex- plored relationships between growth dynamics and climate indices. We compiled the largest ever data set on somatic growth rates for hawksbills – 3541 growth increments from 1980 to 2013. Using generalized addi- tive mixed model analyses, we evaluated 10 covariates, including spatial and temporal variation, that could a ect growth rates. Growth rates throughout the region responded similarly over space and time. The lack of a spatial e ect or spatio-temporal interaction and the very strong temporal e ect reveal that growth rates in West Atlantic hawksbills are likely driven by region-wide forces. Between 1997 and 2013, mean growth rates declined signi cantly and steadily by 18%. Regional climate indices have signi cant relationships with annual growth rates with 0- or 1-yr lags: positive with the Multivariate El Niño Southern Oscillation Index (correlation = 0.99) and negative with Caribbean sea surface temperature (correlation = −0.85). Declines in growth rates between 1997 and 2013 throughout the West Atlantic most likely resulted from warming waters through indirect negative e ects on foraging resources of hawksbills. These climatic in uences are complex. With increasing temperatures, trajectories of decline of coral cover and availability in reef habitats of major prey species of hawksbills are not parallel. Knowledge of how choice of foraging habitats, prey selection, and prey abundance are a ected by warming water temperatures is needed to understand how climate change will a ect productivity of consumers that live in association with coral reefs.
Dam, R.P. van
The management of small rookeries is key to conserving the regional genetic diversity of marine turtle populations and requires knowledge on population connectivity between breeding and foraging areas. To elucidate the geographic scope of the populations of marine turtles breeding at Bonaire and Klein Bonaire (Caribbean Netherlands) we examined the post-breeding migratory behavior of 5 female loggerheads Caretta caretta, 4 female green turtles Chelonia mydas, and 2 male and 13 female hawksbill turtles Eretmochelys imbricata during the years 2004-2013. After leaving Bonaire, the 24 tracked turtles frequented foraging grounds in 10 countries. The distances swum from Bonaire to the foraging areas ranged from 608 to 1766 km for loggerhead turtles, 198 to 3135 km for green turtles, and 197 to 3135 km for hawksbill turtles, together crossing the waters of 19 countries. Males represented the minority in this study, but we made 2 key observations that require further research: males remained in the vicinity of the breeding area for 3-5 mo, which is 2-5 times longer than females, and males migrated greater distances than previously recorded. Although the turtles dispersed widely across the Caribbean, there appeared to be 2 benthic foraging areas of particular importance to all 3 species of marine turtles breeding at Bonaire, namely the shallow banks east of Nicaragua and Honduras (n = 8 tracked turtles) and Los Roques, Venezuela (n = 3). Marine turtles breeding at Bonaire face threats from legal turtle harvesting, illegal take, and bycatch in the waters that they traverse across the Caribbean.
Satellite transmitters were deployed on three green turtles, Chelonia mydas, and two hawksbill turtles, Eretmochelys imbricata, nesting in the Lesser Antilles islands, Caribbean, between 2005 and 2007 to obtain pre- liminary information about the inter-nesting, migratory and foraging habitats in the region. Despite the extremely small dataset, both year-round residents and migrants were iden- tified; specifically, (1) two green turtles used local shallow coastal sites within 50 km of the nesting beach during all of their inter-nesting periods and then settled at these sites on completion of their breeding seasons, (2) one hawksbill turtle travelled 200 km westward before reversing direction and settling within 50 km of the original nesting beach and (3) one green and one hawksbill turtle initially nested at the proximate site, before permanently relocating to an alter- native nesting site over 190 km distant. A lack of nesting beach fidelity was supported by flipper tag datasets for the region. Tagging datasets from 2002 to 2012 supported that some green and hawksbill individuals exhibit low fidelity to nesting beaches, whereas other females exhibited a high degree of fidelity (26 turtles tagged, 40.0 km maximum distance recorded from original nesting beach). Individual turtles nesting on St Eustatius and St Maarten appear to exhibit behavioural plasticity in their inter-nesting behav- iour and post-nesting migration routes in the eastern Carib- bean. The tracking and tagging data combined indicate that some of the green and hawksbill females that nest in the Lesser Antilles islands are year-round residents, whilst oth- ers may nest and forage at alternative sites. Thus, continued year-round protection of these islands and implementation of protection programmes in nearby islands could contrib- ute towards safeguarding the green and hawksbill popula- tions of the region.
2005 was a very successful year for Sea Turtle Conservation Bonaire as we built upon the accomplishments of 2004. In all the program areas, staff and volunteers worked hard to move us forward in pursuit of our mission: to ensure the protection and recovery of Bonaire’s sea turtle population throughout their range.
On the research front, we observed sea turtle nesting in 2005 at lower levels than during 2004, with a total of 61 nests recorded for all the beaches of Bonaire and Klein Bonaire. The in-water surveys on the turtle foraging grounds yielded a total of 105 turtles handled, of which 21 were recaptures from 2003 and 2004. Satellite tracking of breeding turtles was again a success, with four turtles fitted with transmitters: three on hawksbills and one on a loggerhead turtle, all at Klein Bonaire. We successfully followed all tracked turtles during their long-distance migrations to their foraging grounds. We generated daily maps and gave relevant information via our newsletter to the public, creating awareness about the situation of the sea turtles around the globe.
In the area of education and public awareness, our year long education and outreach campaign that started in 2004 and done in collaboration with the Dutch Caribbean Nature Alliance, STINAPA Bonaire, and Coral Resource Management was completed. The very successful and well-received campaign focused on sea turtles and provided a year of constant attention through the distribution of newsletters, posters, flyers, buttons, school and community presentations, beach clean-ups and press releases. Our regularly scheduled ‘Sea Turtles of Bonaire’ slide presentation continued to draw the interested public. During the year, we generated a record number of press releases in our effort to bring attention to sea turtle conservation and alert the public to vital issues.
This last year we were able to take a step forward in the organizational arena. Our staff team grew with the addition of Dr. Robert van Dam as our Scientist Coordinator, Eric van der Keuken as our financial advisor and accountant, and a part-time field assistant. Volunteer support and assistance was significantly increased with the addition of three new island residents contributing their time and talents in a consistent fashion. We were also contacted by scores of people offering to assist on an ad-hoc basis.
Our website and electronic newsletters became important and very effective tools for us to share information about the endangered sea turtles and inform about our continuing efforts to protect these animals.