Data from: Mapping of cetacean and seabird populations in the North-East Atlantic

1.    Distribution maps of cetaceans and seabirds at basin and monthly scales are needed for conservation and marine management.  These are usually created from standardised and systematic aerial and vessel surveys, with recorded animal densities interpolated across study areas. However, as individual surveys have restricted spatial and temporal coverage, distribution maps at basin and monthly scales have previously not been possible.  
2.      This study develops an alternative approach consisting of: (1) collating diverse survey data to maximise spatial and temporal coverage, (2) using detection functions to estimate variation in the surface area covered (km2) among these surveys, standardising measurements of effort and animal densities, (3) developing species distribution models (SDM) that overcome issues with heterogeneous and uneven coverage.  
3.      2.68 million km of survey data in the North-East Atlantic between 1980 and 2018 were collated and standardised. SDM using Generalized Linear Models (GLM) and General Estimating Equations (GEE) in a hurdle-model were developed. Distribution maps were then created for 12 cetacean and 12 seabird species at 10 km and monthly resolution. Qualitative and quantitative assessment indicated good model performance. 
4.      Applications and synthesis: This study provides the largest ever collation and standardisation of diverse survey data for cetaceans and seabirds, and the most comprehensive distribution maps of these taxa in the North-East Atlantic. These distribution maps have numerous applications including the identification of important areas needing protection, and the quantification of overlap between vulnerable species and anthropogenic activities. This study demonstrates how the analysis of existing and diverse survey data can meet conservation and marine management needs.