Can habitat modelling for the octopus Eledone cirrhosa help identify key areas for Risso's dolphin in Scottish waters?

Marine protected areas (MPAs) are becoming increasingly important tools in the conservation of cetaceans. This has led to an interest in the use of species distribution models to predict where cetacean species are likely to occur based on the distribution of environmental variables. However, relationships between cetacean distribution and environmental variables are generally assumed to reflect the environmental preferences of their prey. Thus, understanding the distribution of prey may increase our ability to identify important areas for cetaceans. Here, we describe the diet of Risso's dolphin (Grampus griseus) by analysing stomach contents of individuals stranded in Scotland over the last twenty years. Next, we use habitat modelling to test whether Rissos's dolphin distribution in Scottish waters, as inferred from sightings, is related to the distribution of its main prey, the octopus Eledone cirrhosa. While good models of the relationship between the distribution of E. cirrhosa and environmental variables were obtained, there was no evidence of a relationship between modelled octopus distribution and the occurrence of Risso's dolphins. These results suggest that identifying key areas for its main prey species is unlikely to help identify potential MPAs for Risso's dolphin, at least at the spatial resolution used in this study.