Sea turtles

Sea Turtle Conservation on Bonaire in 2020

Bonaire might have been on lockdown in 2020, but that didn’t keep Sea Turtle Conservation Bonaire from working hard.  Their recently published annual report highlights the latest news concerning sea turtle conservation for the island.  Between monitoring resident populations, nests and deploying a satellite tag, 2020 was a busy year for STCB.

Image from STCB Annual Report

Monitoring

Bonaire’s resident turtle population and nesting turtles are monitored through transect-count surveys and nest patrols. Between the months of May and December, volunteers and staff patrolled the beaches looking for new activities. Once marked, these nests were kept under surveillance and excavated after hatching to calculate hatching success. In addition, 108 in water surveys were conducted, allowing STCB to estimate local populations of 555 green and 70 hawksbill turtles.

Capture-Tag-Recapture

Long-term data on specific turtles is gathered through the capture-tag-recapture project.  Through this effort, recaptured turtles are measured, weighed and checked for signs of fibropapillomatosis to track growth rates and the overall health of the population.  Additional DNA samples provide key insight to the distribution of turtle populations throughout the Caribbean. Using data collected over the past 16 years, STCB has been able to show a slight increase in green turtle populations within Lac Bay.  So far, over 3,500 turtles have been tagged which will continue to provide important information for years to come.

Satellite Tags

Turtles are migratory by nature, spending much of their life in transit. Although there is still much to be learned about their behavior, satellite tracking is giving researchers a never-before-seen glimpse of these routes.  Understanding their migration routes and identifying areas of foraging and nesting will provide important information shaping conservation efforts in the future. STCB has been placing satellite trackers on turtles since 2003.  In 2020, the 26th tracker was placed on “Flappie”, who once tagged, traveled to Aruba before continuing on to the Miskito Cays off the coast of Nicaragua.

Hawksbill turtle. Photo credit: © Marion Haarsma

Sea turtles face a barrage of threats, from being caught as bycatch to degraded habitats from coastal development and climate change.   Conservation groups such as STCB are instrumental for increasing local awareness and driving conservation efforts forward.

Learn more about their important work by visiting STCB’s website (www.bonaireturtles.org) or reading the full annual report, see DCBD link below.

 

https://www.dcbd.nl/sites/default/files/documents/STCB-Year-Report-2020-...

 

Article published in BioNews 45

Date
2021
Data type
Media
Theme
Education and outreach
Research and monitoring
Geographic location
Bonaire
Author

Demographic changes in Pleistocene sea turtles were driven by past sea level fluctuations affecting feeding habitat availability

Abstract

Pleistocene environmental changes are generally assumed to have dramatically af-fected species’ demography via changes in habitat availability, but this is challenging to investigate due to our limited knowledge of how Pleistocene ecosystems changed through time. Here, we tracked changes in shallow marine habitat availability resulting from Pleistocene sea level fluctuations throughout the last glacial cycle (120–14  thou-sand years ago; kya) and assessed correlations with past changes in genetic diver-sity inferred from genome-wide SNPs, obtained via ddRAD sequencing, in Caribbean hawksbill turtles, which feed in coral reefs commonly found in shallow tropical waters. We found sea level regression resulted in an average 75% reduction in shallow ma-rine habitat availability during the last glacial cycle. Changes in shallow marine habitat availability correlated strongly with past changes in hawksbill turtle genetic diver-sity, which gradually declined to ~1/4th of present-day levels during the Last Glacial Maximum (LGM; 26–19   kya). Shallow marine habitat availability and genetic diver-sity rapidly increased after the LGM, signifying a population expansion in response to warming environmental conditions. Our results suggest a positive correlation be-tween Pleistocene environmental changes, habitat availability and species’ demog-raphy, and that demographic changes in hawksbill turtles were potentially driven by feeding habitat availability. However, we also identified challenges associated with disentangling  the  potential  environmental  drivers  of  past  demographic  changes, which highlights the need for integrative approaches. Our conclusions underline the role of habitat availability on species’ demography and biodiversity, and that the con-sequences of ongoing habitat loss should not be underestimated.

 

KEYWORDS: ddRAD sequencing, demographic change, habitat availability, Pleistocene sea turtles, sea level change

Date
2021
Data type
Scientific article
Theme
Education and outreach
Research and monitoring
Geographic location
Aruba
Bonaire
St. Eustatius
St. Maarten

Special Edition: Transboundary Species

There has been a recent increase in public awareness of environmental issues as the effects of climate change have become ever more noticeable in our daily lives. As we enter a new decade, it becomes useful to review what conservation efforts have worked so far, and take inventory of what efforts will be required for the future. Starting with the constitutional referendum creating the Caribbean Netherlands (Bonaire, St. Eustatius and Saba (BES), the response to conservation challenges of all six Dutch Caribbean islands have varied. Since 2010, the BES islands have seen an overall increase in funding support and conservation actions, and therefore presumably also saw greater improvements when compared to Aruba, Curaçao and Sint Maarten, though clearly not enough (Sanders et al, 2019).

The goal of this Transboundary Species special edition of BioNews is to provide an update on the latest published research results and highlight the need for transboundary protection. These species know no boundaries, and thus move between the Dutch Caribbean islands and beyond. Their protection will require broadscale conservation efforts which cover the entire Caribbean, including the six Dutch Caribbean islands. Collaboration between all six islands is of the utmost importance. This is one of the Dutch Caribbean Nature Alliance’s (DCNA) main goals: working together and sharing skills, knowledge and resources to maintain a solid network and support nature conservation in the entire Dutch Caribbean.

 

Date
2019
Data type
Media
Theme
Education and outreach
Research and monitoring
Geographic location
Aruba
Bonaire
Curacao
Saba
Saba bank
St. Eustatius
St. Maarten
Author

Construction setback regulations and sea-level rise: Mitigating sea turtle nesting beach loss

Global sea-level rise of up to 0.6 m is predicted in the next 100 years. In areas where coastal structures prevent landward mi- gration of beaches, a major impact of sea-level rise will be a loss of beach habitat, with repercussions for beach-dependent organ- isms such as sea turtles. Setback regulations, which prohibit construction within a set distance from the sea, have the potential to mitigate loss of beach area by providing a buffer zone which allows for the natural movement of beaches in response to perturbation. The potential impact of a rise in sea level on 11 important sea turtle nesting beaches in Barbados under a range of setback regu- lations was determined. Three sea-level rise scenarios were modelled under five different setback regulations (10, 30, 50, 70 and 90 m). Beach area was lost from all beaches under all sea-level rise scenarios with a 10 and 30 m setback, from some beaches with a 50 m setback and from one beach with a 70 m setback. No beach area was lost with a 90 m setback distance. Sea turtles nest within a range of beach elevations and there was an overall loss of beach habitat within the preferred nesting elevation range with both a 10 and 30 m setback under all sea-level rise scenarios. Considerable variation in the extent of beach and nesting area loss was observed. The implementation and enforcement of adequate setback regulations have the potential to maintain the ecological and economic function of beaches in the face of extensive coastal development and sea-level rise. 

Date
2008
Data type
Scientific article
Geographic location
Bonaire

Trends in Kemp’s Ridley Sea Turtle (Lepidochelys kempii) Relative Abundance, Distribution, and Size Composition in Nearshore Waters of the Northwestern Gulf of Mexico

Long-term monitoring of in-water life history stages of the critically endangered Kemp’s ridley sea turtle (Lepidochelys kempii) is essential for management because it generates information on the species’ at-sea abundance, size composition, distribution, and habitat requirements. We documented trends in Kemp’s ridley size, relative abundance, and distribution using entanglement netting surveys at three study areas adjacent to tidal passes in the northwestern Gulf of Mexico (NWGOM) during intermittent sampling periods from 1991 to 2013. A total of 656 Kemp’s ridley sea turtles were captured ranging in size from 19.5 to 66.3 cm straight carapace length (SCL) (mean 1⁄4 35.0 cm SCL). The dominance of juveniles (25–40 cm SCL) captured during sampling suggests the nearshore waters of the NWGOM are an important developmental foraging ground for Kemp’s ridley. Characterization of Kemp’s ridley long-term relative abundance reveals a generally stable trend in catch- per-unit-effort (CPUE) across all study areas combined. Based on the increasing trend in the number of hatchlings released from the species’ primary nesting beach, Rancho Nuevo, Mexico, since the early 1990s, the lack of a corresponding overall increase in juvenile abundance at nearshore sampling locations is puzzling. This disparity is most likely an artifact of the present study’s sampling design, but could also indicate shifts in Kemp’s ridley recruitment away from the NWGOM. While conservation efforts have contributed to this species’ overall growth since the 1980s, as measured by the increasing number of nests, recent declines in this rate of increase are a concern and call for a more comprehensive approach to managing Kemp’s ridley recovery efforts. 

Date
2016
Data type
Scientific article
Theme
Research and monitoring

Kemp’s Ridley Sea Turtle (Lepidochelys kempii) Nesting on the Texas Coast: Geographic, Temporal, and Demographic Trends Through 2014

Kemp’s ridley (Lepidochelys kempii) is the world’s most endangered sea turtle species, and nests primarily on the Gulf of Mexico coast in Mexico. In 1978, a binational project was initiated to form a secondary nesting colony of this species in south Texas at Padre Island National Seashore (PAIS), as a safeguard against extinction. During 1978–2014, we documented 1,667 Kemp’s ridley nests in Texas, with 56% found at PAIS. Most nests (89%) found in south Texas were from wild-stock turtles; south Texas is the northern extent of the documented historic nesting range for the species. We documented nesting in north Texas starting in 2002, and most nests (53%) found there were from turtles that had been head-started (reared in captivity for 9–11 mo), and released off the Texas coast as yearlings. Kemp’s ridley nesting increased in Texas during the mid-1990s through 2009, before annual nest numbers dropped in 2010, rebounded and plateaued in 2011 and 2012, and then decreased again in 2013 and 2014. Annual numbers of nests found in Texas and Mexico followed similar trends and were correlated (R2 1⁄4 0.95). We examined nesting turtles for presence of tags at 55% of the nests located in Texas. Of the Kemp’s ridleys we examined during 2000–14, the annual percentage of apparent neophytes decreased and the annual percentage of remigrants increased over time. Mean annual remigration intervals of Kemp’s ridleys increased steadily from 1.9 yr in 2008 to 3.3 yr in 2014. These changes in demographic parameters are critical to understanding the recent fluctuation in the number of nesting Kemps ridleys and will be used in population models to investigate possible causes of the recent and sudden decline of nesting Kemp’s ridleys in Texas and Mexico. 

Date
2016
Data type
Scientific article
Theme
Research and monitoring

A Historical Perspective of the Biology and Conservation of the Kemp’s Ridley Sea Turtle

The history of the critically endangered Kemp’s ridley sea turtle (Lepidochelys kempii) has presented scientists and conservationists with a variety of questions and challenges originating in part from the species’ limited distribution and single primary nesting beach. Although the species was initially brought to the attention of the scientific community in 1880 by Richard Kemp, more than 80 yr passed before Henry Hildebrand revealed the location of its primary nesting beach at Rancho Nuevo, Mexico in the western Gulf of Mexico. By the time scientists began estimating the number of females nesting at Rancho Nuevo, it appeared that the species had declined when compared with the relatively large mass nesting (a.k.a. arribada) filmed by Andres Herrera in 1947. This decline appeared to be due to historic exploitation of turtles and their eggs on the nesting beach and accidental capture in the Gulf of Mexico shrimp fishery. Despite the implementation of conservation measures at Rancho Nuevo, the species continued to decline until the mid-1980s. The continued protection of females and nests on the nesting beach, the decline in shrimping effort in the Gulf of Mexico, and the implementation of turtle excluder devices resulted in a significant increase in the number of females nesting during the 1990s, and an exponential recovery rate. Since 2010, the recovery rate has unexpectedly deviated from its exponential trend and sharp declines have been documented in some years. The underlying cause(s) of the recent decline is unclear. 

Date
2016
Data type
Scientific article
Theme
Research and monitoring

Introduction to the Special Issue on the Kemp’s Ridley Sea Turtle (Lepidochelys kempii)

The Kemp’s ridley sea turtle (Lepidochelys kempii) is an iconic Gulf of Mexico species and an enduring symbol of restoration and recovery. Its population declined dramatically during the 1960s and 1970s after decades of egg harvest and incidental capture in fisheries. By the mid-1980s only a few hundred female Kemp’s ridleys came ashore to lay eggs on their nesting beaches in the Mexican state of Tam- aulipas. Conservation practices implemented to reduce mortality and increase recruitment saved the species from extinction and led to exponential growth in the number of adult female Kemp’s ridleys from the few hundred turtles counted in 1985 to nearly 10,000 turtles by 2009. This outcome is one of the greatest wildlife conservation successes of our time.

One valuable lesson learned is that sea turtle restoration is slow, but possible, if threats are reduced or removed, and recruitment into the population is sustained at high levels. Key to the success of the initial Kemp’s ridley recovery were the intensive conservation actions and coopera- tion of two nations; federal, state, and local resource agencies; nongovernmental organiza- tions; industry; hundreds of volunteers; and the funding made available for recovery.

There are many key events that contributed to saving the Kemp’s ridley from extinction (Hep- pell et al., 2007). Most notable, however, is the combination of long-term protection of nesting beaches, requiring the use of turtle excluder devices on shrimp fishing vessels in U.S. and Mexican waters, seasonal and spatial closures to shrimp fishing in critical habitat, and the reduction in shrimp fishing effort in the Gulf of Mexico. Collectively, these actions led to a increase in the number of Kemp’s ridley nests in Mexico and Texas, an expansion of their nesting range in the Gulf of Mexico, and the impressive population growth observed through 2009 (Hep- pell et al., 2007; Crowder and Heppell, 2011).

Unfortunately, the recovery of the Kemp’s ridley slowed substantially after 2009 and corre- lated spatially and temporally with multiple natural and anthropogenic stressors in the Gulf of Mexico. In response to concerns about the species and its status, Texas Sea Grant and the Gladys Porter Zoo cohosted the Second Interna- tional Kemp’s Ridley Sea Turtle Symposium in November 2014 to provide a timely forum for the presentation and discussion of recent advances in the science, conservation, and management of this endangered species. The papers in this special issue were presented at the symposium and greatly advance our knowledge of the biology of the species, the history of conservation efforts that saved it from extinction, and the impacts of recent stressors in the Gulf of Mexico. 

Date
2016
Data type
Scientific article
Theme
Research and monitoring
Author

Global analysis of the effect of local climate on the hatchling output of leatherback turtles

The most recent climate change projections show a global increase in temperatures along with precipitation changes throughout the 21st century. However, regional projections do not always match global projections and species with global distributions may exhibit varying regional susceptibility to climate change. Here we show the e ect of local climatic conditions on the hatchling output of leatherback turtles (Dermochelys coriacea) at four nesting sites encompassing the Paci c, Atlantic and Indian Oceans. We found a heterogeneous e ect of climate. Hatchling output increased with long-term precipitation in areas with dry climatic conditions (Playa Grande, Paci c Ocean and Sandy Point, Caribbean Sea), but the e ect varied in areas where precipitation was high (Pacuare, Caribbean Sea) and was not detected at the temperate site (Maputaland, Indian Ocean). High air temperature reduced hatchling output only at the area experiencing seasonal droughts (Playa Grande). Climatic projections showed a drastic increase in air temperature and a mild decreas in precipitation at all sites by 2100. The most unfavorable conditions were projected for Sandy Point where hatching success has already declined over time along with precipitation levels. The heterogeneous e ect of climate may lead to local extinctions of leatherback turtles in some areas but survival in others by 2100. 

Date
2015
Data type
Scientific article
Theme
Research and monitoring
Document