Sei whale movements and behaviour in the North Atlantic inferred from satellite telemetry

The stock structure of the sei whale Balaenoptera borealis in the North Atlantic is unknown, despite years of commercial hunting. New and up-to-date data on distribution and movements are essential for the creation of plausible hypotheses about the stock structure of this species. Between 2008 and 2009 satellite tracks of 8 sei whales were obtained, 7 during spring and 1 in late September. Using a hierarchical switching state-space model we investigated the movements, behaviour and the role of distinct areas in their life history. Two distinct phases corresponding to migratory and foraging movements were identified. A migratory corridor between the Azores and the Labrador Sea is clearly identifiable from the data. Behaviour consistent with foraging was observed frequently in the Labrador Sea, showing that it constitutes an important feeding ground. A link between the Labrador Sea and other feeding grounds to the east is deemed likely. The data also support a discrete feeding ground in the Gulf of Maine and off Nova Scotia. A possible link between the feeding grounds in the Labrador Sea and wintering grounds off northwestern Africa is proposed.