Larval behaviours are predicted to impact their long-term spreading, with wider spreading being everywhere associated with more time spent higher in the water column. The strength of this enhanced dispersal varies regionally (from strong to very strong). Dispersal pathways are predicted to be affected by larval behaviour in ways which could influence the distribution of species. For deep-sea populations, the uncertainty in modelled dispersal and connectivity associated with vertical larval positioning in the water column is potentially an order of magnitude larger than that associated with pelagic larval duration or model hydrodynamics. The knowledge gaps in larval behaviour which contribute most to the uncertainty concern settling – the age at which larvae start to sink, and the sinking rate. In the absence of detailed knowledge of larval development, time-series observations of larval position in the water column could be used to constrain models, hugely reducing uncertainty in predictions. Under the most dispersive behaviour modelled, populations throughout the North Atlantic would be connected. Seamount populations may be crucial stepping stones in this wider connectivity. In the more dispersive scenarios two large-scale closed connectivity loops were identified, one anticlockwise around the North Atlantic basin with west-east return via the Azores, the second smaller loop following the sub-polar gyre. Even for the least dispersive behaviour modelled, populations along the continental slope may be connected anticlockwise around the North Atlantic, depending on the detailed habitat distribution. These conclusions are based on a large, systematic Lagrangian modelling experiment, tracking about 10 million virtual particles over 50 years in contrasting dynamical regimes around the North Atlantic Ocean.

10.5281/zenodo.3548344