Distribution, size range and growth rates of hawksbill turtles at a major foraging ground in the eastern Pacific Ocean

Abstract

ABSTRACT.Hawksbill sea turtles (Eretmochelys imbricata) inhabiting the eastern Pacific Ocean are one of the world's most threatened marine turtle management units. Despite the fact that knowledge about the status of sea turtles at foraging grounds is a key element for developing the effective conservation strategies, comprehensive studies of hawksbills at foraging habitats in the eastern Pacific remain lacking. For many years anecdotal information indicated Coiba Island National Park in Panama as a potentially important hawksbill foraging ground, which led to the initiation of monitoring surveys in September 2014. Ongoing mark-recapture surveys to assess population status, generate demographic data and identify key foraging sites have been conducted every six months in the park since that time. To date, a total of six monitoring campaigns consisting of four days each have been conducted, leading to the capture and tagging of 186 hawksbills, 51 of which were recaptured at least once. The size range of captured individuals was 30.0 to 75.5 cm and largely comprised of juveniles. Somatic growth rates of individual hawksbills were highly variable, ranging from -0.78 to 7.1 cm year -1 . To our knowledge, these are the first published growth rates for juvenile hawksbill turtles in the eastern Pacific Ocean. When these growth data are combined with information on hawksbill demography and distribution, our findings indicate Coiba Island National Park is one of the most important known foraging sites for hawksbill sea turtles in the eastern Pacific Ocean.

Trophic ecology of hawksbill turtles (Eretmochelys imbricata) in Golfo Dulce, Costa Rica: integrating esophageal lavage and stable isotope (δ13C, δ15N) analysis

“…All hawksbills were captured in waters of 7 m or shallower. This pattern has been reported for other sites in the EP (Diez et al, 2003;Gaos et al, 2012aGaos et al, , 2016Carrión et al, 2013;Llamas et al, 2017), indicating that they live in shallow areas, likely related to food availability, with greater food densities and diversity in shallow waters (Meylan, 1988;León & Bjorndal, 2002;Carrión et al, 2013).…”

“…This is the first study to combine oesophageal lavage and stable nitrogen and carbon isotope analyses in eastern Pacific sea turtles, and to our knowledge is also the first-ever published stable isotope study for hawksbills in this region. The information obtained in this research contributes to the knowledge of the foraging behaviour and general biology of hawksbills (Gaos et al, 2012b;Carrión et al, 2013;Heidemeyer et al, 2014;Chacón et al, 2015;Llamas et al, 2017), and our data show that coastal waters of Golfo Dulce offer important shelter and food for this critically endangered species Carrión et al, 2013). Moreover, the hawksbill's apparent fidelity to this area-as evidenced by numerous recapturesunderscores the need to protect the habitats and prey resources present in Golfo Dulce (Chacón et al, 2015).…”

“…The presence of a 39.5 cm (CCL) individual suggests this site hosts hawksbills that have recently recruited from open ocean habitats. Postoceanic juveniles have also been reported at other areas along the Pacific coast including Punta Coyote (minimum CCL 36 cm; Carrión et al, 2013), Matapalito Bay (minimum CCL = 31 cm), in the Gulf of Nicoya (Heidemeyer et al, 2014), and Coiba National Park (minimum CCL = 30 cm) (Llamas et al, 2017). Coupled with our data, these observations indicate that eastern Pacific hawksbills recruit to coastal habitats with a CCL ≥ 30 cm, and show that the Pacific coast of Costa Rica is an important area for juveniles recruiting to coastal habitats after completing their oceanic juvenile phase.…”

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

“…Traditionally, the main focus of research in marine turtles has been on nesting beaches (Bjorndal 1999). Yet, long-term studies in foraging areas have contributed to our knowledge on the general foraging ecology of marine turtles , Bjorndal et al 2000, Meylan et al 2011, and more recent studies have focussed on patterns of recruitment, how much time turtles spend in these areas and at what age and size they are expected to reach maturity and leave those habitats (Krueger et al 2011, Patrício et al 2011, Bell & Pike 2012, Colman et al 2015, Llamas et al 2017. There is still a need, however, for a more complete understanding of immature life stages, including population dynamics, survival rates and habitat use (Rees et al 2016, Wildermann et al 2018.…”

Filling the gaps in sea turtle research and conservation in the region where it began: Latin America

“…Two studies revealed new foraging habitats. Llamas et al (2017) The third group of studies focused on several of the long-standing anthropogenic threats facing sea turtle: incidental catch (also known as bycatch) and illegal take (Wallace et al, 2011). Liles et al (2017) investigated the impact of the lobster gillnet fishery in Central America and estimated one of the highest rates of gillnet bycatch and mortality for hawksbill turtles anywhere in the world.…”