A super-group of humpback whales (Megaptera novaeangliae) in a krill no take zone at South Georgia

The Western South Atlantic humpback whale population is almost or completely recovered, following intensive whaling around South Georgia, chiefly between 1904 and 1916. One of the consequences of recovery is the formation of foraging super-groups of whales, which are challenging to count. Here, we counted a humpback whale super-group which was observed inside a krill No-Take Zone at Clerke Rocks off South Georgia in November 2025. A Poisson process was used to model the number of expected, apparently random visual cues (whale blows) which were photographed and filmed. Correcting for availability bias due to breath-hold diving, we estimated 710 (95% CI: 620–820) humpback whales. Estimating group size separately, by eye, under-counted by 36–53%. The super-group was reminiscent of a pre-whaling account in 1904 by C.A. Larsen of an exceptionally large aggregation of humpback whales at the same location. Although an isolated observation, it raises the possibility that progressive fisheries measures may be benefiting large krill predators in a Southern Ocean No Take Zone which merits further investigation.