Fisheries and Oceans Canada, 501 University Crescent, Winnipeg, MB, Canada.
Department of Earth Sciences, The University of Western Ontario, London, ON, Canada.
Sci Rep. 2021 Mar 24;11(1):6739. doi: 10.1038/s41598-021-86272-5.
Killer whales (Orcinus orca) are distributed widely in all oceans, although they are most common in coastal waters of temperate and high-latitude regions. The species' distribution has not been fully described in the northwest Atlantic (NWA), where killer whales move into seasonally ice-free waters of the eastern Canadian Arctic (ECA) and occur year-round off the coast of Newfoundland and Labrador farther south. We measured stable oxygen and carbon isotope ratios in dentine phosphate (δO) and structural carbonate (δO, δC) of whole teeth and annual growth layers from killer whales that stranded in the ECA (n = 11) and NWA (n = 7). Source δO of marine water (δO) at location of origin was estimated from dentine δO values, and then compared with predicted isoscape values to assign individual distributions. Dentine δO values were also assessed against those of other known-origin North Atlantic odontocetes for spatial reference. Most ECA and NWA killer whales had mean δO and estimated δO values consistent with O-depleted, high-latitude waters north of the Gulf Stream, above which a marked decrease in baseline δO values occurs. Several individuals, however, had relatively high values that reflected origins in O-enriched, low-latitude waters below this boundary. Within-tooth δO ranges on the order of 1-2‰ indicated interannual variation in distribution. Different distributions inferred from oxygen isotopes suggest there is not a single killer whale population distributed across the northwest Atlantic, and corroborate dietary and morphological differences of purported ecotypes in the region.
虎鲸（Orcinus orca）广泛分布于所有海洋，但在温带和高纬度地区的沿海水域最为常见。该物种在北大西洋西北部（NWA）的分布尚未完全描述，虎鲸会进入东加拿大北极（ECA）季节性无冰水域，并在更靠南的纽芬兰和拉布拉多海岸常年出现。我们测量了在 ECA（n = 11）和 NWA（n = 7）搁浅的虎鲸牙齿的牙本质磷酸盐（δO）和结构碳酸盐（δO、δC）中的稳定氧和碳同位素比值。从牙齿的 δO 值估算了原始产地的海水源 δO（δO），然后将其与预测的等距值进行比较，以分配个体分布。还根据其他已知的北大西洋齿鲸的牙本质 δO 值评估了 ECA 和 NWA 虎鲸的牙本质 δO 值，以进行空间参考。大多数 ECA 和 NWA 虎鲸的平均 δO 和估计的 δO 值与海湾流以北的 O 贫、高纬度水域一致，在该水域之上，基线 δO 值会显著下降。然而，有几个个体的相对较高值反映了其起源于该边界以下的 O 丰富、低纬度水域。牙齿内 δO 值范围在 1-2‰左右，表明分布存在年际变化。氧同位素推断出的不同分布表明，在北大西洋西北部没有一个分布广泛的虎鲸种群，并且证实了该地区所谓生态型的饮食和形态差异。
