Predicting habitat suitability for basking sharks (Cetorhinus maximus) in UK waters using ensemble ecological niche modelling

Abstract

The basking shark (Cetorhinus maximus) is an endangered species in the north-east Atlantic, having been historically over exploited. Whilst near-shore aggregation hotspots in the UK have been identified, robust knowledge on species distribution and abundance outside these areas remains limited. Research techniques, such as habitat modelling, could however be used to gain a greater knowledge of the species distribution to inform management plans to aid population recovery. For large mobile species gathering wide-scale distribution data can be financially and logistically challenging. In lieu of conducting a UK-wide expensive strategic survey for basking sharks, we use data from two regional-scale surveys, which were conducted in southwest England and western Scotland, and use an Ensemble Ecological Niche Model (EENM) to produce a spatially explicit map of habitat suitability. When compared against a ~20-year database of public sightings of basking sharks across UK coastal seas (to 6 nautical miles offshore), patterns of habitat suitability yielded a statistically significant agreement with areas known to support basking shark sightings. EENMs could be used to advise Marine Protected Area (MPA) selection, as well as to inform environmental impact assessments for offshore developments. The application of EENM outputs could be wide-reaching and benefit not only basking sharks but other large mobile marine species in the north-east Atlantic.