Data for, "Contrasting abundance trajectories for recovering baleen whales under rapidly changing human pressures in the Antarctic Peninsula region" GCB

Data for publication. Abstract Since the discovery of abundant whale and seal populations in the 1800s, the Southern Ocean ecosystem has been shaped by nearly two centuries of human exploitation, from industrial whaling and sealing to contemporary krill fishing. Currently, many Southern Ocean predator populations are characterized by steep population trajectories emblematic of a system undergoing considerable change. To further our understanding of the current role of recovering baleen whale populations in Southern Ocean ecosystems, we sought to estimate abundance for fin, humpback and Antarctic minke whales foraging in the Antarctic Peninsula region, a seasonal hotspot for biological productivity and the focal point of human activities in Antarctica. We developed a cost-effective method for collecting standardised distance sampling data for cetaceans from Antarctic tourist vessels over four Antarctic summer (November-March) sampling seasons (2021/2022 - 2024/2025). We estimate summer abundance for fin (28,345, CV = 0.34), humpback (32,990, CV = 0.12) and Antarctic minke (2,024, CV = 0.33) whales which suggested an intrinsic annual abundance increase across the last two decades (since the year 2000) for fin +13.1% p.a. (95% CI: +7.1-19.3% p.a.) and humpback +6.7% p.a.(95% CI: +2.5-11.0% p.a.) whales and an intrinsic annual decrease for Antarctic minke whales -2.7% p.a.(95% CI: -6.3-1.1% p.a.). Spatial predictions of density indicate that fin, humpback, and Antarctic minke whales forage in discrete, largely non-overlapping regions, consistent with body-size-structured habitat partitioning which is potentially the result of competition among whale species. Abundance trends mirror this pattern, with fin whales, the largest and presumably most efficient foragers, showing most rapid increase, humpback whales showing moderate increase, and Antarctic minke whales likely declining. In a region undergoing rapid environmental change and intensifying human use, these abundance estimates highlight the re‑emergence of baleen whales as key krill predators, reinforcing the need to account for recovering whale populations in krill‑fishery management.