Stay off the motorway: Resolving the pre-recruitment life history dynamics of the European anchovy in the SW Mediterranean through a spatially-explicit individual-based model (SEIBM)

We explore the underlying mechanisms of the early life history dynamics of the European anchovy, Engraulis encrasicolus, in the SW Mediterranean. By using a 3D ROMS hydrodynamic model coupled to an individual-based model (IBM) of the larval stages of the European anchovy, we tested the following hypotheses: (1) the plausible effective spawning zones (those generating late larvae to the known nursery grounds) are mainly found in the vicinity of Malaga Bay, as suggested by published empirical data; (2) the observed, back-calculated growth of larvae sampled in the nursery grounds can be reasonably simulated by a simple temperature-dependent growth model; and (3) the inclusion of biological behavior in the IBM significantly improves the match between the observed and modeled late-larval recruitment and/or growth patterns. We performed simulations for the peak spawning season in 2008, for which survey data were available, and an average climatological run. Hypothesis 1 was accepted, whereas hypothesis 2 resulted in a good imitation of anchovy growth only after 10 days post-hatch. The inclusion of an empirically derived equation for egg buoyancy in the model (hypothesis 3) resulted in a slight improvement of the model of late-larval recruitment patterns. Finally, our model was used to explore possible retention-based nursery areas in the whole Alboran Sea. Our simulations showed to agree well with the existing data both in the European and in the African coast and confer the physics a dominant role in shaping the spatial dynamics of early life stages of anchovy in the area.

► The Atlantic Jet spatially modulates the anchovy spawning in the SW Mediterranean.
► Growth of surviving larvae over 10 days old is reasonably well predicted by a T-dependent IBM.
► Eggs buoyancy has an effect on late-larval recruitment.
► Larval demographic connectivity with African and/or Atlantic sources is unlikely.
► Likely changes in the jet dynamics may affect anchovy populations.