Implications of temporal variability in larval dispersal for fish populations and fisheries on coral reefs

Larval dispersal by ocean currents is crucial for many marine species’ life cycles, yet temporal variability in dispersal remains poorly understood. Using a 20-year timeseries of biophysical simulations, we model how dispersal variability can impact reef fishery populations. Even when metapopulations are fished at supposedly sustainable levels (40% unfished biomass), temporal variation in larval dispersal alone can drive up to a third of local populations below depleted thresholds. When metapopulations are depleted to 20% of unfished biomass, up to 60% of local populations drop below 10% unfished biomass, where key ecological functions are unlikely to be maintained. This risk is particularly acute in metapopulations where larval settlement patterns are volatile and/or spatially synchronised. Finally, we observe recovery of depleted populations, following fishery closures, can vary by over a decade depending on post-closure dispersal patterns. These findings expose how dispersal variability creates substantial, previously unrecognized risks for marine population management.