Identifying Suitable Areas for Common Bottlenose Dolphins in Anthropized Waters

Understanding the processes that determine the occurrence of species, especially for those exposed to human activities, is the key to appropriate management. Despite Tursiops truncatus being well-studied worldwide, information about transient groups of this common bottlenose dolphins and how groups are exposed to human activities is lacking. Here, we modelled and mapped how the environment and human activities drives bottlenose dolphin habitat suitability, and residence patterns in an anthropized area of the Southwestern Atlantic Ocean. We ran 300 distribution models, including six algorithms, and generated an ensemble model to predict the habitat suitability of the species. In parallel, we used photo-identification techniques to evaluate dolphins' degree of residence pattern. Primary productivity, seabed slope and port activities explained dolphins’ habitat suitability. The most suitable areas for bottlenose dolphins included coastal waters, nearby port complexes and shipping routes. We also identified a low degree of residence in Cabo Frio and Rio de Janeiro city waters, but calves were constantly sighted there, indicating an important area for caring and nursing. The high overlap between the dolphins’ most suitable areas and human activities, such as ports, vessel traffic and fisheries spots, plus the presence of calves in these areas, highlights the need for safeguard measurements to protect these animals from threats. In addition, our results may be used to support management decisions, such as fisheries regulations and the creation of new marine protected areas to conserve critical habitats of this species.