Abstract
Crown-of-thorns starfish (COTS) are a leading cause of coral decline on the Great Barrier Reef (GBR), with the majority of their impact occurring during outbreaks. These outbreaks involve rapid increases in populations followed by abrupt declines, and spread between reefs via larval dispersal—a key process in COTS reproduction. Given the difficulty in quantifying dispersal empirically, predictions are instead formed using coupled models of ocean currents and larval biology. Previous efforts have linked dispersal models to COTS population dynamics, however do so indirectly, or at spatiotemporally limited scales. Using an improved set of dispersal estimates and expanded COTS monitoring data, we assess the role of dispersal in determining a reef’s susceptibility to outbreaks. Our results indicate that while there is minimal evidence that dispersal patterns alone drive outbreaks, once combined with COTS population data it becomes clear that dispersal still plays a major role. By predicting COTS populations on undersampled reefs, we estimate that, on average, reefs that have experienced an outbreak receive 50–100% more larvae than those that have not. This is irrespective of whether we assume reefs hold their long-term predicted average COTS abundance, or their predicted maximum abundance. Given the difficulty in directly validating dispersal models, these results provide evidence that highlights their utility in understanding marine population dynamics. Furthermore, our results emphasise the critical role of resolving dispersal networks in guiding COTS control efforts. Specifically, they indicate that suppressing larval production through culling may reduce the risk of outbreaks on downstream reefs connected via larval dispersal.