Dispersion of East Pacific green turtle hatchlings emerging from Nombre de Jesús, Costa Rica

GABRIELA S. BLANCO; STEPHEN J. MORREALE; FRANK V. PALADINO; JAMES R. SPOTILA

Hobart

Workshop; Tagging through the stages workshop at Biologging IV; 2011

SCIRO Marine and Atmospheric research

We designed and developed a program to estimate the dispersion of East Pacific green turtle hatchlings emerging Nombre de Jesús, Costa Rica. First we created a DOS program using FWTools and phyton script, then passed the output to a spatially explicit model we created using ArcInfo Workstation to simulate the trajectory produced by oceanic surface currents on an ideal planktonic particle. All in all, the model simulates a hatchling drifting with the currents in the uppermost layer of the water column. We tested three scenarios releasing the hatchling 10 km off: 1-Nombre de Jesús in peak hatchling season (1st week of December), 2- Nombre de Jesús in non hatchling season (1st week of June) and 3-same latitude as the nesting beach, but in the southern hemisphere. Simulated hatchlings showed a broad dispersion from Nombre de Jesús with the southernmost location 1º 35? S off Ecuador, the northernmost location 14º 30? N off southern Mexico and 115ºW in the Pacific Ocean. We found three different scenarios in which hatchlings could be dispersed depending upon the year of emergence. 1- modeled hatchlings were transported to oceanic waters and after three months were pushed back closer to the coast 2- hatchlings were transported north or south remaining close to the coast for the whole year and 3- hatchlings were transported to waters off the coast for the whole year but still within the Eastern Tropical Pacific (ETP). Areas with concentration of hatchlings concur with adult foraging areas suggesting that adult feeding grounds are in locations where hatchlings are naturally deposited by the currents. The magnitude of currents in the southern hemisphere was significantly lower than those near Nombre de Jesús suggesting that the oceanography in the ETP provides a unique area for hatchling development. The main oceanic characteristics related to the hatchling dispersal were the Costa Rican Dome (CRD) associated with the eddies produced by the Tehuantepec, Papagayo and Panama jets. The eddies and the CRD have associated a high biological productivity which would provide hatchlings with the necessary resources for development. This model was the first attempt to simulate the hatchling dispersion from Pacific Costa Rica and provided insights into the possible early life stage of the East Pacific green turtles.