Krill finder: Spatial distribution of sympatric fin (Balaenoptera physalus) and humpback (Megaptera novaeangliae) whales in the Southern Ocean

Fin (Balaenoptera physalus, Linnaeus 1758) and humpback (Megaptera novaeangliae, Borowski 1781) whales feed during the austral summer in Antarctic waters. Despite the spatial (two-dimensional) sympatry of both species, they exhibit trophic segregation (three-dimensional). We used multitemporal presence-only data of fin and humpback whales and Antarctic krill (Euphausia superba, Dana 1852) combined with environmental variables to produce species distribution models (SDMs). We aimed to (1) determine the environmental suitability in the Southern Ocean for fin and humpback whales and krill, with field validation in a region of interest, (2) calculate the areas of spatial overlap between the two whale species and between the whales and krill and (3) quantify the presence of the target species within the protected areas from the world database on protected areas (WDPA). All the SDMs had high performances, with AUC and TSS values higher than 0.8. On a circum-Antarctic scale, fin whales had northern distributions, while humpbacks had southern distributions. There was a spatial overlap of 47% between whales and 16% between them and krill. Nearly 92% of fin whale sightings overlapped spatially with their binary predictions, this value was 91% for humpback whales. For fin whales, 2% of their environmental suitability was projected in some WDPA areas, this value was 4% for humpback whales and 15% for krill. Despite international efforts, the environmental niches of target species are partially protected by the WDPA, mainly where the spatial overlap between species was greatest. The anthropic and climatic pressures that Antarctica is experiencing challenge us to propose new responsible scientific responses to environmental dynamics and biodiversity.