Basking sharks and oceanographic fronts: quantifying associations in the north-east Atlantic

1. Understanding the mechanisms that link oceanographic processes and marine vertebrate space use is critical to our knowledge of marine ecosystem functioning, and for effective management of populations of conservation concern. 2. The basking shark Cetorhinus maximus has been observed in association with oceanographic fronts – physical interfaces at the transitions between water masses – exploiting foraging opportunities resulting from zooplankton aggregation. However, the scale, significance and variability of these associations have not previously been established. 3. Here, we quantify the influence of thermal and chlorophyll-a fronts on basking shark habitat use in the north-east Atlantic. We use animal-mounted archival tracking together with composite front mapping via Earth Observation (EO) remote sensing to provide an oceanographic context to shark movements. 4. We investigate levels of association with fronts occurring over two spatio-temporal scales, (i) broad-scale, seasonally...