Using marine mammal habitat modelling to identify priority conservation zones within a marine protected area

One common approach to marine conservation is the designation of marine protected areas (MPAs). Marine mammals have been proposed as a target species for such areas due to their role as indicators of ecosystem processes. In NE Scotland, a large multiple-use MPA has been designated to protect bottlenose dolphins Tursiops truncatus. We used broad-scale surveys throughout this MPA to model habitat preferences of different marine mammals. We aimed to investigate the degree of overlap between distributions of different species, the environmental factors influencing their distributions, and the effect of spatial scale on the significance of different environmental predictors. Bottlenose dolphins had a primarily coastal distribution with localised areas of intense use, in contrast to harbour porpoises Phocoena phocoena, harbour seals Phoca vitulina and grey seals Halichoerus grypus, which were widely dispersed throughout the MPA. At larger scales (4 x 4 km grid cells), seal distribution was significantly related to depth, seabed slope, distance to shore and mean sea surface salinity, whereas at the smallest scale (1 x 1 km grid cells), sediment type was also important. This study demonstrated the hierarchical pattern of distributions, with areas of high relative density occurring within a broader protected area that the animals were known to regularly frequent. Habitat preference models therefore provide a valuable tool for determining which areas should be given highest conservation priority and for identifying key locations for further research on interactions between these species and anthropogenic stressors.