Killer whale () population dynamics in response to a period of rapid ecosystem change in the eastern North Atlantic.

This study investigates survival and abundance of killer whales () in Norway in 1988-2019 using capture-recapture models of photo-identification data. We merged two datasets collected in a restricted fjord system in 1988-2008 (Period 1) with a third, collected after their preferred herring prey shifted its wintering grounds to more exposed coastal waters in 2012-2019 (Period 2), and investigated any differences between these two periods. The resulting dataset, spanning 32 years, comprised 3284 captures of 1236 whales, including 148 individuals seen in both periods.

Isotopic niche differs between seal and fish-eating killer whales () in northern Norway.

Ecological diversity has been reported for killer whales () throughout the North Atlantic but patterns of prey specialization have remained poorly understood. We quantify interindividual dietary variations in killer whales ( = 38) sampled throughout the year in 2017-2018 in northern Norway using stable isotopic nitrogen (δN: N/N) and carbon (δC: C/C) ratios. A Gaussian mixture model assigned sampled individuals to three differentiated clusters, characterized by disparate nonoverlapping isotopic niches, that were consistent with predatory field observations: seal-eaters, herring-eaters, and lumpfish-eaters.

First longitudinal study of seal-feeding killer whales (Orcinus orca) in Norwegian coastal waters.

Killer whales (Orcinus orca) have been documented preying on either fish or marine mammals in several regions, suggesting that this odontocete species has the ability to specialize on different types of prey. Off Norway, killer whales have been shown to rely on the Atlantic herring (Clupea harengus) as a main prey resource. Infrequent observations have revealed seals as an additional component of their diet, yet the extent of predation on marine mammals has remained largely unknown.

Arctic marine mammal population status, sea ice habitat loss, and conservation recommendations for the 21st century.

Arctic marine mammals (AMMs) are icons of climate change, largely because of their close association with sea ice. However, neither a circumpolar assessment of AMM status nor a standardized metric of sea ice habitat change is available. We summarized available data on abundance and trend for each AMM species and recognized subpopulation.