Species Distribution Model of Cetaceans in Relation to Environmental Factors at Two Locations in the North Atlantic

Abstract

Cetaceans in the North Atlantic are under threat from the increasing pressure and demand placed on the sea by humans. In order to conserve cetacean populations, legislative acts such as the EC Habitats Directive (Council Directive 92/43/EEC) are calling for protected areas to be established. Species distribution models have been used in this study as a tool to outline habitat preference of cetaceans in the Celtic Sea and eastern North Atlantic, helping to determine the boundaries for protected areas. Remotely-sensed environmental data was analysed against visual boat survey data using boosted regression tree modelling. A review of the literature emphasised the need for site specific analysis due to the variability in physical oceanographic processes. This was reflected in the results with the most important variable being chlorophyll at Baltimore and water depth at Penzance. The optimal depth was calculated at 30 – 50 m for both sites. The optimal range of chlorophyll was between 1.8 – 2.5 mgm-3 with an increase in cetacean sightings towards the upper limit. A preferred sea surface temperature of 14.6 – 15 °C was found at the Baltimore site and 15.5 – 15.6 °C was found at the Penzance site. The need for fine scale analysis of oceanographic properties and their relation to species distribution is recognised, as well as an expansion of this study to capture the full range of environmental variability at these locations.