Modelling marine larval dispersal: a cautionary deep-sea tale for ecology and conservation

Abstract Larval dispersal data are increasingly sought after in ecology and marine conservation, the latter often requiring information under time limited circumstances. Basic estimates of dispersal are often used in these situations acknowledging their oversimplified nature. Larval dispersal models (LDMs) are now becoming more popular and may be a tempting way of refining predictions, but prior to targeted groundtruthing their predictions are of unknown worth. This case study uses deep-sea LDMs to compare predictions of dispersal. Two LDMs driven by different example hydrodynamic models are compared, along with an informed estimate based on mean current speed and planktonic larval duration (PLD) to provide insight into predictive variability. LDMs were found to be more conservative in dispersal distance than an estimate. This difference increased with PLD which may result in a bigger disparity for deep-sea species predictions. Although LDMs were more spatially targeted than an estimate, the two LDM predictions were also significantly different from each other and would result in contrasting advice for marine conservation. These results show a greater potential for model variability than previously appreciated by ecologists and strongly advocates groundtruthing predictions before use in management. Advice is offered for improved model selection and interpretation of predictions.