Data from: Behavioural estimation of blue whale movements in the Northeast Pacific from state-space model analysis of satellite tracks

Baleen whale migrations typically consist of annual movements between productive, high-latitude feeding grounds and unproductive, low-latitude breeding grounds. However, the actual migratory path and whales’ behaviour in these locations are poorly known. The objectives of this study were to apply a switching state-space model to the satellite tracks of blue whales Balaenoptera musculus in the Northeast Pacific to improve location estimation and gain insight into the migratory (transiting) and foraging (area-restricted search, ARS) behaviours of this population. During the period 1993 to 2007, Argos satellite tags were attached to 159 whales, mainly off the coast of California during late summer, of which 92 tracks were >7 d in duration. There was generally a southward movement during the winter to Baja California and to an area west of the Costa Rica Dome, in the eastern tropical Pacific (ETP). Travel speeds during transit were significantly faster than during ARS movements (mean = 3.70 and 1.05 km h^–1, respectively). On average, 29% of the track time was spent in ARS, and the mean time within an ARS patch was 21 d. The occurrence of ARS behaviour throughout the migration cycle suggests that these animals may forage year-round, but could also indicate limited movements during the reproductive season. The extent of their northward migration from Baja California to Washington varied significantly interannually, likely in response to environmental changes affecting their prey. The long track durations obtained from electronic tagging have provided essential new information about the critical habitats of Northeast Pacific blue whales.

须鲸（Baleen whale）的洄游通常表现为年度往返于高纬度高产摄食场与低纬度低产繁殖场的移动。然而，这类鲸类的实际洄游路径与在上述栖息环境中的行为却鲜为人知。本研究旨在通过对东北太平洋蓝鲸（Balaenoptera musculus）的卫星追踪轨迹应用状态空间转换模型（switching state-space model），以优化位置估算精度，并解析该种群的洄游（行进）与觅食（区域限制性搜索，ARS）行为模式。1993年至2007年间，研究人员为159头鲸佩戴了Argos卫星标签（Argos satellite tags），标记工作主要于夏末在加利福尼亚近岸海域开展，其中92条追踪轨迹的持续时长超过7天。冬季时，鲸群通常会向南迁徙至下加利福尼亚半岛，以及东热带太平洋（ETP）内的哥斯达黎加海隆（Costa Rica Dome）西侧海域。行进阶段的移动速度显著快于区域限制性搜索活动阶段（平均速度分别为3.70 km·h⁻¹与1.05 km·h⁻¹）。平均而言，追踪时长中有29%的时间用于区域限制性搜索行为，单个区域限制性搜索聚集区内的平均停留时长为21天。在整个洄游周期中均观测到区域限制性搜索行为，这表明该种群可能全年都在觅食，但也可能意味着它们在繁殖季的移动范围有限。它们从下加利福尼亚半岛向华盛顿州的北向洄游范围存在显著的年际差异，这大概率与影响其猎物的环境变化有关。通过电子标记技术获得的长时程追踪数据，为东北太平洋蓝鲸的关键栖息生境提供了至关重要的全新认知。