Data for, "Habitat partitioning mediates contrasting abundance trajectories for recovering whale species"

Data for publication. 

Authors

Angus F. Henderson^.1*, Sophie Bestley ^.1, Elling D. Johannessen^.2, Mary-Anne Lea ^1.3, Verena Meraldi ^.4, Cecilia Passadore ^.5, Ryan R. Reisinger ^.6, Federico G. Riet Sapriza ^.7, Mercedes Santos ^.8, Victoria Warwick-Evans ⁹, Nat Kelly ^.10

Abstract

The recovery of populations following a major perturbation is governed by intrinsic growth rates, density-dependent processes, and carrying-capacity limitations associated with resource and habitat availability. Baleen whale populations were decimated by industrial whaling of the 20^th century, with many of these populations recovering and again exserting considerable influence across the Southern Ocean ecosystem. However, species and populations of baleen whales appear to be recovering variably, and the drivers which govern this process is not well understood. We aimed to elucidate possible drivers of contrasting populations trajectories by estimating abundance and trajectories for three species of baleen whale. To do this we developed a cost-effective method for collecting standardized distance sampling data for cetaceans from Antarctic tourist vessels and estimate summer abundance for fin (N=28,345), humpback (N=32,990) and Antarctic minke (N=2,024) whales. These results revealed an intrinsic annual increase across the last two decades for fin and humpback whales (+13.1 and +6.7% y-1. respectively) and an intrinsic annual decrease for Antarctic minke whales (-2.7% y-1). Spatial density patterns reveal discrete, largely non-overlapping foraging habitats, consistent with body size-structured niche partitioning and competitive exclusion across the foraging grounds. Abundance trends parallel this pattern, with the largest species, fin whales increasing most rapidly, and the smallest Antarctic minke whales likely declining, revealing possible ecological drivers of diverging recoveries of the great whales under increasingly constrained access to profitable krill foraging patches.