Variability in transport of fish eggs and larvae. I. Modelling the effects of coastal reclamation

Dispersal of eggs and larvae of herring, plaice and sole in the southern North Sea was studied by modelling using real-time hydrodynamic forcing (with wind, air pressure and river discharge) and species-specific knowledge of larval behaviour (incorporating salinity triggers), temperature-dependent growth and spawning characteristics. Larval transport was simulated using a finite-volume advection-diffusion model (Delft3D-WAQ) coupled to a 3-dimensional hydrodynamic model (Delft3D-FLOW). Model parameter settings were refined following a sensitivity analysis. Validation of modelled hydrodynamics and larval distribution patterns showed broad agreement with field data. Differences in model results for larval distribution, transport success and timing of arrival at nursery grounds between baseline conditions and a scenario that incorporated a proposed 1000 ha coastal reclamation (protruding 6 to 7 km from the Dutch coastline) for the expansion of the Port of Rotterdam (Maasvlakte-2) were insignificant in comparison to the interannual variability in larval dispersal for these species. Results suggest that effects of the proposed coastal reclamation on the transport success of fish larvae (flatfish and herring), an issue over which public stakeholders had expressed concern, will be negligible.