Ziphius cavirostris presence relative to vertical and temporal variability of oceanographic conditions in the southern california bight

The oceanographic conditions of the Southern California Bight (SCB) dictate the distribution and abundance of prey resources and therefore the presence of mobile predators, such as goose-beaked whales (Ziphius cavirostris). Goose-beaked whales are deep-diving odontocetes that spend a majority of their time foraging at depth. Due to their cryptic behavior, little is known about how they respond to seasonal and interannual changes in their environment. This study utilizes passive acoustic data recorded from two sites within the SCB to explore the oceanographic conditions that goose-beaked whales appear to favor. Utilizing optimum multiparameter analysis, modeled temperature and salinity data are used to identify and quantify these source waters: Pacific Subarctic Upper Water (PSUW), Pacific Equatorial Water (PEW), and Eastern North Pacific Central Water (ENPCW). The interannual and seasonal variability in goose-beaked whale presence was related to the variability in El Niño Southern Oscillation events and the fraction and vertical distribution of the three source waters. Goose-beaked whale acoustic presence was highest during the winter and spring and decreased during the late summer and early fall. These seasonal increases occurred at times of increased fractions of PEW in the California Undercurrent and decreased fractions of ENPCW in surface waters. Interannual increases in goose-beaked whale presence occurred during El Niño events. These results establish a baseline understanding of the oceanographic characteristics that correlate with goose-beaked whale presence in the SCB. Furthering our knowledge of this elusive species is key to understanding how anthropogenic activities impact goose-beaked whales.南加州湾（Southern California Bight, SCB）的海洋水文条件决定了猎物资源的分布与丰度，进而影响鹅喙鲸（Ziphius cavirostris）这类移动型捕食者的栖息分布。鹅喙鲸为深潜齿鲸类，绝大多数时间都在深海觅食。由于其行为极为隐秘，目前学界对其如何响应环境的季节与年际变化仍知之甚少。本研究依托南加州湾内两个站点获取的被动声学监测数据，探究鹅喙鲸偏好的海洋水文环境特征。本研究采用最优多参数分析方法，结合模拟得到的温度与盐度数据，对三类源水进行识别与定量：北太平洋亚寒带上层水（Pacific Subarctic Upper Water, PSUW）、赤道太平洋水（Pacific Equatorial Water, PEW）以及东太平洋北中部水（Eastern North Pacific Central Water, ENPCW）。鹅喙鲸的栖息分布存在显著的季节与年际变化，该变化与厄尔尼诺-南方涛动事件的波动，以及上述三类源水的占比和垂直分布特征密切相关。观测显示，鹅喙鲸的声学检测频次在冬、春季达到峰值，夏末与初秋时段则有所下降。这类季节性种群增长的时段，恰好对应加利福尼亚潜流中PEW占比升高、表层海水中ENPCW占比降低的时期。年际尺度上，鹅喙鲸的检测频次在厄尔尼诺事件期间出现上升。本研究结果为厘清南加州湾内与鹅喙鲸栖息相关的海洋水文特征奠定了基准认知。进一步了解这一难以捉摸的物种，是理解人类活动如何影响鹅喙鲸的核心前提。