Modelling the distribution of a critically endangered cold-water coral, Isidella elongata, in the Mallorca channel

Ward Standaert

The bamboo coral Isidella elongata is often associated with a diverse community of fauna. Therefore it plays an important role as a biodiversity hotspot including commercially valuable species. However, it was assessed as a critically endangered species by the IUCN due to its disappearance, which is mainly related to the harmful effect of trawl fisheries. Management practices are required in order to protect and preserve this species. But, knowledge on the fine-scale distribution is still very limited. In this study, habitat suitability models were build based on a dense population of I. elongata, found in the Mallorca channel (western Mediterranean), to fill this knowledge gap. Generalized additive models, Maximum entropy models and Random Forest were combined into an ensemble model. Models performed well and showed that habitat is most suitable on smooth plains surrounding the two seamounts of the study area. Furthermore, two models out of three show a preference of the coral for low roughness, which can be related to flat areas. The predictions of the habitat suitability models presented in this study can be used to design protection measures, such as an area closed for fishing as proposed by the authors as a theoretical exercise.