Data from: A model for simulating the active dispersal of juvenile sea turtles with a case study on western Pacific leatherback turtles

Oceanic currents are known to broadly shape the dispersal of juvenile sea
turtles during their pelagic stage. Accordingly, simple passive drift
models are widely used to investigate the distribution at sea of various
juvenile sea turtle populations. However, evidence is growing that
juveniles do not drift purely passively but also display some swimming
activity likely directed towards favorable habitats. We therefore present
here a novel Sea Turtle Active Movement Model (STAMM) in which juvenile
sea turtles actively disperse under the combined effects of oceanic
currents and habitat-driven movements. This model applies to all sea
turtle species but is calibrated here for leatherback turtles (Dermochelys
coriacea). It is first tested in a simulation of the active dispersal of
juveniles originating from Jamursba-Medi, a main nesting beach of the
western Pacific leatherback population. Dispersal into the North Pacific
Ocean is specifically investigated. Simulation results demonstrate that,
while oceanic currents broadly shape the dispersal area, modeled
habitat-driven movements strongly structure the spatial and temporal
distribution of juveniles within this area. In particular, these movements
lead juveniles to gather in the North Pacific Transition Zone (NPTZ) and
to undertake seasonal north-south migrations. More surprisingly, juveniles
in the NPTZ are simulated to swim mostly towards west which considerably
slows down their progression towards the American west coast. This
increases their residence time, and hence the risk of interactions with
fisheries, in the central and eastern part of the North Pacific basin.
Simulated habitat-driven movements also strongly reduce the risk of
cold-induced mortality. This risk appears to be larger among the juveniles
that rapidly circulate into the Kuroshio than among those that first drift
into the North Equatorial Counter Current (NECC). This mechanism might
induce marked interannual variability in juvenile survival as the strength
and position of the NECC are directly linked to El Niño activity.