Estimates of the mortality and the duration of the trans‐Atlantic migration of European eel Anguilla anguilla leptocephali using a particle tracking model

Abstract

Using Lagrangian simulations, based on circulation models over three different hydroclimatic periods in the last 45 years in the North Atlantic Ocean, the trans-Atlantic migration of the European eel Anguilla anguilla leptocephali was simulated via the passive drift of particles released in the spawning area. Three different behaviours were modelled: drifting at fixed depth, undergoing a vertical migration or choosing the fastest currents. Simulations included mortality hypotheses to estimate a realistic mean migration duration and relative survival of A. anguilla larvae. The mean migration duration was estimated as 21 months and the mortality rate as 3.8 per year, i.e. < 0.2% of A. anguilla larvae may typically survive the trans-Atlantic migration.

The Genetic Consequences of Spatially Varying Selection in the Panmictic American Eel (Anguilla rostrata)

“…By considering only the earliest life stages, we may fail to catch differential selection acting later in the life cycle. While we cannot rule it out, the fact that most of the mortality occurs before entering freshwater (Bonhommeau et al 2009) reduces this possibility. Moreover, it is likely that selection acting at later life stages plays on different sets of genes.…”

“…Consequently, the temporal stability of the observed genetic patterns between the GLASS8 and GLASS9 categories probably reflects the repeated action of similar natural selection pressures in the two consecutive year cohorts covered by this study. Given that only a very small proportion (,0.5%) of the larvae survive until glass eels reach the coasts and that the glass eel survival rate is 10% (Bonhommeau et al 2009), our sampling scheme was designed with the intent to detect changes in allelic frequencies occurring during the early stages of eels' life Figure 2 Synthetic multilocus spatial variation component in the 2008 glass eels. The spatial component analysis was based on genetic variation at the eight loci significantly associated with explanatory variables in the GLASS8 category.…”

Navigating the flow: individual and continuum models for homing in flowing environments

“…Formally, drifters are organisms/particles that simply float and are convected by currents: certain studies assume this if active movement is smallish (e.g. [12]), yet it must be considered carefully since even small amounts of oriented swimming can alter overall behaviour [10,11]. A navigator corresponds to an organism that actively swims, periodically assessing its environment and biasing its active direction accordingly.…”

“…Lagrangian-based particle models are often employed for the IBM, with each individual indexed by its instantaneous position and velocity: navigation can be incorporated via a directional bias according to orienteering cues. Currents can be obtained from widely available datasets and models based on these principles have been applied to understand movement dynamics across aquatic and airborne populations: the advection-dominated movement of fish larvae [8]; the role of current-directed movement in jellyfish blooms [9]; the influence of directed movement on turtle drifting within ocean currents [10,11]; the Atlantic movements of eel larvae [12]; how wind influences the choice of staging sites during red knot migration [13]; the exploitation of favourable winds by high-flying insects [14]. For many further references and examples, see [15,16].…”

“…Interface 12: 20150647 various studies approximate as such if active movement is believed negligible compared to the flow (e.g. [12]). Drifters simply correspond to zero speed, s ¼ 0, and expressions (2.4) and (2.5) are zero, regardless of the turning distribution.…”