A benign technique for mapping coral distribution in the closed areas of the Rockall Plateau

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Cold-water corals (Lophelia spp.) occur throughout the north east Atlantic and have been identified in bottom trawl records occurring in abundant patches on the Rockall Plateau. As a result, several large areas have been closed to bottom trawling to protect this habitat. However, our understanding of the distribution of deep-water coral remains poor. A non-destructive visual survey method using a deep towed camera system was deployed to collect data on the occurrence of Lophelia spp. around the closed areas at Rockall. The species distribution model (SDM) Random Forest was used to predict the potential spatial distribution of Lophelia spp. and infer the environmental requirements of the species. The model used coral presence-absence data from the towed camera survey and the trawl record data. Performance was evaluated by partitioning the data into ‘training’ and ‘testing’ data. The model showed good performance based on Cohen’s Kappa and the area under the curve of the receiver operator characteristic curve. Depth, aspect, and slope were the most important environmental variables for predicting the presence of Lophelia spp. The predictive map suggests that potential Lophelia habitat occurs most abundantly along the west of the plateau in a depth range of 200 – 400 m.