Temporal variability of larval connectivity for scallops in the Gulf of Maine and Scotian Shelf region–a model sensitivity study

Abstract Ecological science, effective fisheries management, and conservation all benefit from an understanding of how larval dispersal links geographically distinct regions. An important but understudied aspect of such connectivity is how it can vary on different time scales. Using a high-resolution biophysical model, this study examines the temporal variability of larval connectivity of the Atlantic sea scallop (Placopecten magellanicus) due to spawning across interannual, seasonal, intra-month, and tidal scales in the Gulf of Maine and Scotian Shelf. The results reveal substantial interannual variability, with an average coefficient of variation (CV) of 44% for the major connectivity pathways, and suggest that the large-scale oceanographic changes strongly influence interannual variations of larval transport. Seasonal variations are also significant: larvae spawned in spring experience longer pelagic larval durations (PLDs) due to cooler temperatures, while fall-spawned larvae grow faster, resulting in shorter PLDs. On the intra-month time scale, the average CV is 26% for the major connectivity pathways, with the connectivity variability at this scale exceeding interannual variability in certain regions. Additionally, this study shows that tidal processes play a key role in changing larval transport pathways in regions with strong tidal currents, such as Georges Bank and the Bay of Fundy. These high-frequency connectivity fluctuations are introduced by the timing of larval spawning relative to tidal phases, which, in turn, are driven by the periodic spatial shifts of the Lagrangian coherent structures in ocean flows. The findings underscore the need to take into account multi-scale temporal variability into larval dispersal models in order to capture those fluctuations to accurately represent connectivity patterns and inform management strategies.