Abstract
Aim: Deep‐diving cetaceans are oceanic species exposed to multiple anthropogenicpressures including high intensity underwater noise, and knowledge of theirdistribution is crucial to manage their conservation. Due to intrinsic low densities,wide distribution ranges and limited presence at the sea surface, these species arerarely sighted. Pooling data from multiple visual surveys sharing a common linetransectmethodology can increase sightings but requires accounting for heterogeneityin protocols and platforms.Location: North Atlantic Ocean and Mediterranean Sea.Time period: 1998 to 2015.Major taxa: Ziphiidae; Physeteriidae; Kogiidae.Methods: About 1,240,000 km of pooled effort provided 630 sightings of ziphiids,836 of physeteriids and 106 of kogiids. For each taxon, we built a hierarchicalmodel to estimate the effective strip width depending on observation conditionsand survey types. We then modelled relative densities in a generalized additivemodelling framework. Geographical predictions were limited to interpolationsidentified with a gap analysis of environmental space coverage.Results: Deeper areas of the North Atlantic gyre were mostly environmental extrapolationin the predictions, thereby highlighting gaps in sampling across the differentsurveys. For the three species groups, the highest relative densities werepredicted along continental slopes, particularly in the western North AtlanticOcean where the Gulf Stream creates dynamic frontal zones and eddies.Main conclusions: Pooling a large number of surveys provided the first basin‐widemodels of distribution for deep‐diving cetaceans, including several data‐deficienttaxa, across the North Atlantic Ocean and the Mediterranean Sea. These models canhelp the conservation of elusive and poorly known marine megafauna.