Monday, March 12, 2012

Reporting from the 32nd International Sea Turtle Symposium, Huatulco, Oaxaca, Mexico

Every year, the International Sea Turtle Society convenes for the annual conference where science research, conservation, and all the inspiring and creative work combining these areas is shared among sea turtle biologists and enthusiasts from around the world.  Last year, the 31st Annual International Sea Turtle Symposium (ISTS) was hosted in our home town of San Diego! This year, the ISTS is in our neighbor to the south, Mexico, in the beautiful town of Bahias de Huatulco in the state of Oaxaca.

At last year’s ISTS, I shared my research that was focused on the green sea turtles (Chelonia mydas) that live in the San Diego Bay as well as a project designed to help sea turtle conservation groups be as efficient as possible (A Diagnostic Tool for Marine Turtle Conservation Success). This year at the conference, which officially kicks off tomorrow, Sunday, I’ll be sharing my research that I’ve begun for my doctoral research.

Over the next week, I’ll be sharing not only more of the research I’ll be doing, but I’ll also be sharing all of the incredible talks and events which I’ll be participating in as part of the 32nd Annual ISTS.

On Sunday and Monday I’ll be participating in a two-day workshop all about climate change and sea turtles that is being run by biologist Marianne Fish of the WWF. Then on Monday evening, the full ISTS begins. Tuesday-Friday will be filled with talks, discussions and workshops. On Wednesday I’ll be helping put on a workshop for local students that is being run by Frances Kinney of the Ocean Connectors program, and on Thursday we are hosting a similar workshop for local teachers. Saturday and Sunday will be opportunities to explore the region and its incredible wildlife. 

Stay tuned for more!

Sunday, March 4, 2012

Research being presented at the 2012 International Sea Turtle Symposium

This year, the 32nd annual International Sea Turtle Symposium (ISTS) is being held in Huatulco, Oaxaca Mexico the week of March 11-17.  At this year's annual meeting, I will be presenting my work that I've begun for my doctoral dissertation. 

Detecting ontogenetic shifts and elucidating the "lost years" of East Pacific green turtles (Chelonia mydas) using stable isotope analysis with skeletochronology.

Calandra N. Turner Tomaszewicz1, C. Kurle1, H. Peckham2, V. de la Toba2, J.M. Rodriguez-Baron2, B. MacDonald3, J.A. Seminoff3

1 Ecology, Behavior & Evolution Section, Biological Sciences Department, University of California, San Diego, La Jolla, CA USA 2 Grupo Tortuguero de las Californias, La Paz, Baja Sur California, Mexico 3NOAA-Southwest Fisheries Science Center, La Jolla, CA USA


Me with the stranded turtle at Playa San Lazaro, Baja
The East Pacific green turtle (Chelonia mydas) a.k.a. 'black turtle' population along the Pacific coast of Mexico is listed separately from global green turtles on the U.S. Endangered Species Act, and this population is currently considered Endangered. Cross-border international efforts to protect this population over the past 30 years have curbed the dramatic population decline that was representative of the black turtles in the last century. Green turtles of Pacific Mexico, like green turtles around the worldare subject to varying threats, presenting managers with unique conservation challenges. Distinct risks, environmental conditions and population trends necessitate specific management strategies for these separate populations. Assessing basic turtle biology during the entire life cycle has been identified as a key research priority for all populations of marine turtles. The age-at-settlement, when juvenile turtles undergo an ontogenetic shift from oceanic to neritic habitats, remains unknown for most marine turtle stocks, and better information on the timing of this shift will facilitate more accurate risk assessment and population estimates for management purposes. 

A humerus bone of a dead-stranded green sea turtle (Chelonia mydas)

Stable isotope analysis has been applied to marine turtle humerus bones and scute keratin to identify foraging habitat of marine turtle populations across the globe. This is made possible due to the fact that tissues such as bone and keratin are comprised of nutrients garnered in foraging areas, and these hard inert tissues record isotope signatures from multiple years’ worth of foraging. When an animal moves among spatially discrete food webs that are isotopically distinct, stable isotope values of its tissues can provide unambiguous information about its previous location. Additionally, skeletochronology has been used to estimate age of marine turtles. Using the two together, on adjacent bone or scute samples, allows a determination of the stable isotope values of specific growth layers, which in the case of humerus bones are believed to be annular. Thus, isotopes and skeletochronology has the potential to decipher what habitat types are occupied during sequential years of life. Stable carbon (δ13C) and nitrogen (δ15N) isotope analysis will be conducted on humeri bones from green turtles stranded along the Pacific coast of the Baja California Peninsula, Mexico and from within the Gulf of California. These data will later be linked with skeletochronology and isotope analysis of bone and scute material to elucidate ontogenetic shifts of individual turtles from green turtles in this region. The goal of our research is to gain a better understanding of the duration of the pelagic juvenile stage (i.e. the “lost years”) of green turtles along the Pacific coast of Mexico. Through this unique combination of stable isotope analysis of bone and scute with skeletochronology we hope to determine the age-at-settlement for this recovering population of green turtles and improve understanding of green turtle ontogeny.