Modelling settlement in open populations of reef fishes

Processes that act on individual larvae or on whole larval cohorts can affect settlement patterns in open marine populations. The interaction of these processes is explored using an individual-based simulation model in which the temporal pattern of settlement is the culmination of spawning, larval mortality, and larval duration. The model yielded a wide range of settlement patterns derived from a single spawning pattern. Sensitivity analyses indicate temporal settlement distributions are robust to the mortality rate but are sensitive to the variance associated with larval duration. We applied real data on coral reef fishes (larval production and settlement) to our model to generate hypotheses concerning the influence of cohort-wide and individual processes on their larval lives. Settlement of four out of six species was well matched by our model. Results of species matched by our model showed an approximately equal balance of cohort-wide and individual processes on larval mortality. Results for two species suggest individual-based factors predominantly influence larval duration, while results for another suggest cohort-wide processes predominate. That the settlement of two species was not adequately described using this model suggests additional factors, such as larval behaviour, should be considered by future modelling efforts.