Fine scale daily movements and habitat use of East Pacific green turtles at a shallow coastal lagoon in Baja California Sur, Mexico Jesse Senko a, ⁎, Volker Koch b , William M. Megill c , Raymond R. Carthy a , Robert P. Templeton c , Wallace J. Nichols d a Florida Cooperative Fish and Wildlife Research Unit, USGS Biological Resources Division, Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, FL 32611, USA b Universidad Autónoma de Baja California Sur, Departmento de Biología Marina, Carretera al Sur km 5.5, 23080 La Paz, BCS, Mexico c Department of Mechanical Engineering, Ocean Technologies Laboratory, University of Bath, Bath, BA2 7AY, UK d Ocean Revolution and California Academy of Sciences, Davenport, CA 95017, USA abstract article info Article history: Received 16 April 2010 Received in revised form 14 June 2010 Accepted 14 June 2010 Keywords: Baja California Sur, Mexico Daily movements Fine scale Green turtle Habitat use Vagility Green turtles spend most of their lives in coastal foraging areas where they face multiple anthropogenic impacts. Therefore, understanding their spatial use in this environment is a priority for conservation efforts. We studied the fine scale daily movements and habitat use of East Pacific green turtles (Chelonia mydas) at Laguna San Ignacio, a shallow coastal lagoon in Baja California Sur, Mexico where sea turtles are subject to high levels of gillnet bycatch and directed hunting. Six turtles ranging from 44.6 to 83.5 cm in straight carapace length were tracked for short deployments (1 to 6 d) with GPS-VHF telemetry. Turtles were active throughout diurnal, nocturnal, and crepuscular periods. Although they moved greater total distances during daytime, their speed of travel and net displacement remained consistent throughout 24-h periods. A positive selection for areas of seagrass and moderate water depth (5 to 10 m) was determined using Ivlev's electivity index, with neutral selection for shallow water (b 5 m) and avoidance of deep water (N 10 m). Turtles exhibited two distinct behavioral movement patterns: circular movements with high fidelity to the capture– release location and meandering movements with low fidelity to the capture–release location. Our results indicate that green turtles were active throughout the diel cycle while traveling large distances and traversing multiple habitats over short temporal scales. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Many large marine vertebrates (e.g. marine mammals, sharks, seabirds, and sea turtles) are vulnerable to overexploitation due to their life history characteristics, such as long lifespans, late maturity, slow reproductive rates, and extended migrations (Baum et al., 2003; Fujiwara and Caswell, 2001; Lewison et al., 2004a,b). These animals are important for maintaining ecosystem function and their removal can lead to cascading ecological changes (Fujiwara and Caswell, 2001; Lewison et al., 2004b). Like other large marine vertebrates, when abundant, sea turtles play key ecological roles as consumers, prey and competitors, hosts for parasites and pathogens, substrates for epibionts, seascape and marine substrate engineers, and nutrient transporters (Bouchard and Bjorndal, 2000; Bjorndal, 2003; Bjorndal and Bolten, 2003; Bjorndal and Jackson, 2003). Green turtles (Chelonia mydas) are especially important in coastal areas because their grazing behavior significantly reduces nutrient cycling times in seagrass pastures (Moran and Bjorndal, 2005, 2007). Although once one of the most abundant large vertebrates in the Pacific Ocean, East Pacific green turtles have declined precipitously since the 1950s due to intense commercial fisheries (Marquez et al., 1982; Marquez 1990) and egg harvesting (Clifton et al., 1982; Nichols, 2003). Mexico implemented a management and recovery program in 1978 (Garcia-Martinez and Nichols, 2000), but populations continued to crash and in 1990 the government issued a complete moratorium on the use of sea turtles (Aridjis, 1990). However, despite widespread protection on central nesting beaches and the complete moratorium, current populations remain well below historical levels mainly due to directed hunting and incidental fisheries bycatch (Seminoff, 2004; Koch et al., 2006, 2007). During the past decade sea turtle harvest and bycatch mortality along the Baja California peninsula has been estimated to be as high as 35,000 turtles per year, including at least 7,500 green turtles killed per year (Nichols et al., 2002, 2003; Nichols, 2003), representing a region with one of the highest known sea turtle mortality rates in the world (Gardner and Nichols, 2001; Hays et al., 2003; Nichols and Safina, 2004; Koch et al., 2006; Peckham et al., 2007, 2008; Mancini and Koch, 2009; Mancini, 2009). Journal of Experimental Marine Biology and Ecology 391 (2010) 92–100 ⁎ Corresponding author. Tel.: + 1 203 394 1119. E-mail address: jesse.senko@gmail.com (J. Senko). 0022-0981/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jembe.2010.06.017 Contents lists available at ScienceDirect Journal of Experimental Marine Biology and Ecology journal homepage: www.elsevier.com/locate/jembe