Habitat utilisation by Blainville’s beaked whales off Great Abaco, Northern Bahamas, in relation to seabed topography

We investigated habitat utilization in Blainville's beaked whale, Mesoplodon densirostris, in the northern Bahamas and, as such, this is the first analysis of fine-scale habitat utilization of any member of the genus Mesoplodon. We divided the area into 500x500 m grid squares and each square was assigned a classification for presence or absence of Blainville's beaked whales, along with details of water depth, seabed gradient and seabed aspect. All squares where Blainville's beaked whales occurred had gradients from 68 to 296 m/km and depths from 136 to 1,319 m and most faced northeast compared with 0-526 m/km, 10-3,000 m and all aspects for the whole study area. Generalized additive models and classification trees indicated that, in order of importance, aspect, gradient and depth were related to occurrence of Blainville's beaked whales within the study area. We hypothesize that the relationships between habitat utilization and these topographic variables relates to the effects of interactions between a deepwater current and the seabed topography on preferred prey. Locally, prey animals may be concentrated in areas with a northeast aspect, intermediate gradients and depths between 200 and 1,000 m where the Deep Western Boundary Current is forced towards the surface by the local topography. These are the areas where Blainville's beaked whales preferentially occurred.