Satellite tracking of small juvenile green turtles (Chelonia mydas) in Argentina

GONZÁLEZ CARMAN, VICTORIA; FALABELLA, VALERIA; BRUNO, IGNACIO; DIAZ, LUCRECIA; SVENDSEN, GUILLERMO M; ALBAREDA, DIEGO; MIANZAN, HERMES; CAMPAGNA, CLAUDIO

San Diego

Simposio; 31st Annual Symposium on Sea Turtle Biology and Conservation; 2011

International Sea Turtle Society

This study reports the distribution and oceanographic background of juvenile green turtles (Chelonia mydas) seasonally found in costal waters of Argentina. We deployed satellite transmitters on eight green turtles (mean CCL = 42.4 ± 3.7 cm, range = 38.1 – 47.8 cm, mean weight = 9.5 ± 2.9 kg, range = 6.8 – 14 kg) caught accidentally in the artisanal gillnet fleet of Buenos Aires province during the period 2008-2010. Fixed Kernel method was used to estimate home ranges based on an average of 190 days of transmission per turtle and more than 6700 locations. Instrumented animals remained in the shallow waters of the argentine continental shelf during summer and fall (summer: 50%KDE = 11.3 km2, 95%KDE = 58.7 km2; fall: 50%KDE = 21.1 km2, 95%KDE = 100.4 km2). Preferred habitats were the estuarine areas near Bahía Blanca and Río de la Plata. Animals used only coastal and shallow waters (median = 8.9 m, range = 0 – 57.2 m, n = 1317). By the end of the fall, turtles migrated to southern Brazil, probably triggered by a decreased water temperature. During winter and spring, some turtles remained in deeper waters far from the coast (winter: 50%KDE = 38.7 km2, 95%KDE = 158.7 km2; spring: 50%KDE = 10.5 km2, 95%KDE = 52.8 km2) along the continental shelf break of Brazil and Uruguay. Some other turtles, however, also used near-shore areas of Uruguay and Brazil (median = 53.6 m, range = 0 – 2520 m, n = 1136). Turtles were associated with frontal, highly productive systems in the Río de la Plata and the shelf break. Thus, preferred habitats included not only areas where seagrass or macroalgae grow, but also oceanic or estuarine areas abundant in gelatinous macro zooplankton. To our knowledge, this is the first study documenting seasonal migrations between foraging areas with different diet offers and the use of both neritic and oceanic habitats by small juveniles in the SW Atlantic. These results have conservation relevance because the same turtles that are accidentally captured by Argentinean coastal fisheries could also be captured by coastal and pelagic fisheries of Uruguay and Brazil.