Presence-only habitat suitability models for vulnerable marine ecosystem indicator taxa in the South Pacific have reached their predictive limit

Vulnerable marine ecosystems (VMEs) are typically fragile and slow to recover, making them likely to be substantially altered by disturbance. In the High Seas, regional fishery management organizations (RFMOs) are required to implement measures to prevent significant adverse impacts on VMEs. The objectives of the present study were to: update distribution models of VME indicator taxa in the South Pacific RFMO Convention Area; evaluate these against newly-collated independent field data to test the reliability of the presence-only habitat suitability models; and assess how well the updated models were able to predict into unsampled space. Ensemble habitat suitability models of 10 VME indicator taxa performed well using the newly collated data (AUC > 0.95, TSS > 0.76, and RMSE < 0.34). There were no obvious patterns of decreasing model performance with decreasing environmental coverage; areas with few samples underpinning model predictions still had AUC > 0.93, TSS > 0.71, and RMSE < 0.43. Despite these encouraging results, we also identify some important inherent issues with presence-only models that have profound implications for their use in management of VMEs. Future modelling efforts for VME management purposes should be based ideally on the use of survey presence-absence data and, preferably, abundance data.