Amount and patterns of beluga sightings in the eastern Beaufort Sea

An understanding of the adaptability of belugas (Delphinapterus leucas) to changing ice conditions is required to interpret and predict possible changes in habitat selection in response to projected loss of sea ice throughout the circumpolar Arctic. We analyzed beluga observations made during spring aerial surveys for ringed seals conducted from 1975 to 1979 in the eastern Beaufort Sea. Despite interannual variability in the extent and distribution of sea ice, belugas consistently selected areas with water depths of 200-500 m and heavy ice concentrations (8/10 to 10/10) while areas of open water to light ice concentrations (0/10 to 1/10) were not selected. Belugas were also found in proximity to regions with >0.5 degrees seafloor slope which include the continental slope and other areas with the potential for oceanographic upwellings. In most years (4 of 5), fast-ice edges and coastal areas were not selected. In the lightest ice year analyzed, belugas showed less specificity in habitat selection as their distribution expanded and shifted shoreward to fast-ice edges. The observed distribution is discussed in terms of predator-prey relationships particularly with reference to beluga feeding on polar cod (Boreogadus saida). More research is required to examine and compare possible changes in distribution since the late 1970s and to investigate the factors driving the patterns described.要解读并预测环北极地区海冰预计消退后白鲸（Delphinapterus leucas）栖息地选择的潜在变化，需先明确白鲸对海冰条件变化的适应能力。本研究分析了1975至1979年在波弗特海东部开展的环斑海豹春季航空调查中获取的白鲸观测数据。尽管海冰范围与分布存在年际波动，白鲸始终偏好水深200~500米、冰覆盖率为8/10至10/10的重冰区域，而未选择开阔水域或冰覆盖率为0/10至1/10的轻冰区域。此外，白鲸多分布于海底坡度大于0.5°的区域，包括大陆坡及其他具备海洋上升流潜力的区域。在5个调查年中的4个年份里，白鲸未选择固定冰边缘与近岸区域。在冰情最轻的调查年份中，随着分布范围扩大并向岸迁移至固定冰边缘区域，白鲸的栖息地选择特异性有所下降。本研究结合捕食者-猎物关系（尤其是白鲸以北极鳕鱼（Boreogadus saida）为食的情况）对观测到的白鲸分布特征展开讨论。未来仍需开展更多研究，以对比分析1970年代末以来白鲸分布的潜在变化，并探究塑造该分布模式的驱动因素。