Baleen whales in Macaronesia: occurrence patterns revealed through a bibliographic review

Macaronesia, an oceanic area located in the Northeast Atlantic, exhibits a high topographic and oceanographic complexity that enables a rich biodiversity. So far, seven species of baleen whales have been recorded in the area. These are migratory animals that travel long distances between feeding grounds at high latitudes in summer and tropical areas for mating and breeding in winter. As baleen whales are such mobile animals, the conservation and management of their habitat is highly challenging. Hence, knowing and understanding the patterns of their distribution is fundamental. Despite the many records of baleen whales in Macaronesia, heterogeneity in research effort has resulted in scattered occurrence data that leads to an incomplete picture of their distribution in the area. We aim to increase knowledge of distribution patterns of baleen whales, and identify research effort gaps in Macaronesia. From a total of 14 peer-reviewed publications, four public reports, two poster presentations, and four data bases, we gathered 1798 records in Macaronesia since 1990 for four species of baleen whale: minke whale Balaenoptera acutorostrata, fin whale Balaenoptera physalus, blue whale Balaenoptera musculus, and humpback whale Megaptera novaeangliae. Spatio-temporal descriptive analyses and ecological modelling were carried out in order to understand occurrence patterns. The results show a big lack of research effort and occurrence data in offshore areas and in some coastal waters, namely off the West African coast. Moreover, blue, fin, and humpback whales are sighted mainly in spring in the north of Macaronesia, while minke whale distribution is clearly different: they have a stronger presence in summer. This study highlights areas in urgent need of research effort in order to inform decision-makers and support effective measures for the protection and conservation of baleen whales in Macaronesia.