Available online at www.sciencedirect.com - ... , DEEP-SI<:A RESEARCH _;;, ScienceDirect PART. ELSEVIER Deep-Sea Research I 55 (2008) 646-660 www.elsevier.com/locate/dsri An oceanographic context for the foraging ecology of eastern Pacific leatherback turtles: Consequences of ENSO Vincent S. Saba a ,*, George L. Shillinger b , Alan M. Swithenbank b , Barbara A. Block b , James R. Spotila c , John A. Musick a , Frank V. Paladino d . aDepartment of Fisheries Science, Virginia Institute oj Marine Science, College oj William and Mary, Rt. 1208 Greate Road, Gloucester Point, VA 23062. USA bHopkins Marine Station, StanJord University. 120 Oceanview Boulevard, Pacific Grove, CA 93950, USA CDepartment oj Bioscience and Biotechnology, Drexel Unil'ersity, 3141 Chestnut Street, Philadelphia, PA 19104, USA dDepartment oj Biology, Indiana-Purdue University. 2101 East Coliseum Boulevard, Fort Wayne, IN 46805, USA Received II July 2007; received in revised form 4 February 2008; accepted 17 February 2008 Available online 29 February 2008 Abstract We analyzed some of the primary biological and physical dynamics within the eastern Pacific leatherback turtle (Dermochelys coriacea) migration area in relation to ENSO and leatherback nesting ecology at Parque Nacional Marino Las Baulas (PNMB), Costa Rica. We used data from remote sensing to calculate resource availability via a net primary production (NPP) model, and to analyze the physical dynamics of the migration area via sea surface temperature fronts, Within the migration area, NPP north of 15°S was highly governed by interannual variability as indicated by the Multivariate ENSO Index while south of 15 c S, production had a more seasonal signal. Nesting peaks of leatherbacks at PNMB were associated with cool, highly productive La Nina events and with large-scale equatorial phytoplankton blooms encompassing llOOW that were induced by iron enrichment following the termination of El Nino events, Resource availability in the northern migration arca (eastern equatorial Pacific) appeared to determine the nesting response for the population at PNMB, Costa Rica. We suggest that ENSO significantly influences the nesting ecology of leatherbacks at PNMB because the majority of the population consists of pelagic foragers that strictly rely on the eastern equatorial Pacific for prey consumption prior to the nesting season. Coastal foragers may be a minority in the population because of high mortality rates associated with coastal gillnet fisheries along Central and South © 2008 Elsevier Ltd. All rights reserved. Keywords: Coastal gillnet fisheries; Dermochelys coriacea; Eastern equatorial-southeastern Pacific; ENSO; Leatherback turtle migration; Primary production 1. Introduction The population of leatherback turtles (Dermochelys coriacea) has been declining in the eastern Pacific *Corresponding author. Tel.: + I 8046847551. E-mail address: vssaba@vims.edu (V.S. Saba). 0967-0637/$ - see front matter © 2008 Elsevier Ltd. All rights reserved. doi: 10.1016/j.dsr.2008.02.006 Ocean (Spotila et al., 20(0). Nesting population trends at the major beaches in Costa Rica and Mexico have both shown similar declining trends over the past 15 years (Santidriim-Tomillo et aL, 2007; Sarti-Martinez et al., 2007). Moreover, the eastern Pacific population is the smallest in size and has the lowest reproductive output among all