A major challenge in statistical ecology consists of integrating knowledge from different data sets to produce robust ecological indicators. To estimate species distribution, occupancy models are a flexible framework that can accommodate several data sets obtained from different sampling methods. However, repeating visits at sampling sites is a prerequisite for using standard occupancy models. Occupancy models were recently developed to analyze detection/ non-detection data collected during a single visit. To date, single-visit occupancy models have never been used to integrate several different data sets. Here, we showcase an approach that combines two data sets into an integrated single-visit occupancy model. As a case study, we estimated the distribution of common bottlenose dolphin (Tursiops truncatus) over the northwestern Mediterranean Sea by combining 24,624 km of aerial surveys and 21,464 km of at-sea monitoring. We compared the outputs of single-vs. repeated-visit occupancy models into integrated occupancy models. Integrated models allowed a better sampling coverage of the targeted population, which provided a better precision for occupancy estimates than occupancy models using data sets in isolation. Overall, single-and repeated-visit integrated occupancy models produced similar inference about the distribution of bottlenose dolphins. We suggest that single-visit occupancy models open promising perspectives for the use of existing ecological data sets.

The common bottlenose dolphin (Tursiops truncatus) subpopulation in the Mediterranean is listed as vulnerable by the International Union for Conservation of Nature. This species is strictly protected in France and the designation of Special Areas of Conservation (SAC) is required under the EU Habitats Directive (92/43/EEC). However, little information is available about the structure and dynamics of bottlenose dolphins in French Mediterranean waters. We collected photo-identification data over the whole French Mediterranean continental shelf year round between 2013 and 2015. We sighted 151 groups of bottlenose dolphins allowing the individual photo-identification of 766 animals. The encounter rate distribution showed the presence of bottlenose dolphins over the whole continental shelf year round. We estimated for the first time, using capture-recapture methods, the size of this bottlenose dolphin population at 2,350 individuals (95% credible interval 1,827-3,135). Our results were used in support of the designation of a new dedicated SAC in the Gulf of Lion and provide a baseline for the bottlenose dolphin monitoring in the French Mediterranean waters in the context of the Marine Strategy Framework Directive.

The Mediterranean bottlenose dolphin (Tursiops truncatus) sub-population is listed as vulnerable by the International Union for Conservation of Nature. This species is strictly protected in France and the designation of Special Areas of Conservation (SAC) is required under the European Habitat Directive. However, little information is available about the structure, dynamic and distribution of the population in the French Mediterranean waters. We collected photo-identification data over the whole French Mediterranean continental shelf all year round between 2013 and 2015. We sighted 151 groups of bottlenose dolphins allowing the individually photo-identification of 1,060 animals. The encounter rate distribution showed the presence of bottlenose dolphins over the whole continental shelf all year round. Using capture-recapture methods, we estimated for the first time the size of the bottlenose dolphin resident population at 557 individuals (95% confidence interval: 216-872) along the French Mediterranean continental coast. Our results were used in support of the designation of a new dedicated SAC in the Gulf of Lion and provide a reference state for the bottlenose dolphin monitoring in the French Mediterranean waters in the context of the Marine Strategy Framework Directive.

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