HARP deployment periods and locations.

Understanding abundance and trends of beaked whales in the heavily industrialized Gulf of America (formerly Gulf of Mexico), is critical for management but challenging with visual-based distance-sampling due to their elusive surface behavior. Acoustic-based distance-sampling methods rely on accurate modeling of detection probability as a function of distance from a recorder, requiring population-specific diving and acoustic behavior parameters, which is currently lacking for Gulf populations. To address this, we used passive acoustic tracking with two 4-channel High-Frequency Acoustic Recording Packages (HARPs) deployed off Louisiana (~1100 m depth) in 2021. Echolocation clicks detected on both recorders were localized in 3D to characterize acoustic and diving behavior. These data informed a Monte Carlo cue-based simulation to estimate the probability of detection by a near-seafloor single-sensor HARP. A trial-based approach also estimated detection probability as a function of range to a single-channel sensor deployed at the site. Results show species-specific differences. Goose-beaked whales (Ziphius cavirostris), were detected for longer periods during foraging dives (n = 24 dives, mean: 20.5 min; range: 7–42) compared with Blainville’s (Mesoplodon densirostris, n = 2 dives, 13.6 min; 11–16) and Gervais’ (Mesoplodon europaeus, n = 24 dives, 12.7 min; 7–19) beaked whales. Maximum dive depths also differed, with some goose-beaked whales foraging at or near the seafloor. Descent and ascent rates were similar within species but differed among them (1.34/1.40 m/s for goose-beaked and 1.15/1.19 m/s for Gervais’ beaked whales). Source level and broadband directivity index were estimated at 225 dBpp re 1 μPa-1m and 26 dB for goose-beaked whales, and 218 dBpp re 1 μPa-1m and 20 dB for Gervais’ beaked whales. Estimates were not possible for Blainville’s beaked whales due to limited data. In both the Monte Carlo simulation and trial-based approach, detection probability declined sharply with ranges, reflecting the highly directional beam of beaked whale echolocation clicks.了解工业化程度极高的美洲湾（原墨西哥湾）内喙鲸（beaked whales）的种群丰度与动态趋势，对物种管理而言至关重要；但由于喙鲸的水面活动极为隐匿，基于视觉的距离抽样法难以开展相关调研。基于声学的距离抽样方法，需以声源与记录器的间距为变量构建精准的检测概率模型，而这需要针对特定种群的潜水与声学行为参数，但目前美洲湾种群的此类参数仍存在空白。为解决这一问题，本研究于2021年在路易斯安那州外海（水深约1100米）部署了两套4通道高频声学记录包（High-Frequency Acoustic Recording Packages, HARPs），开展被动声学追踪。研究人员对两台记录器捕获的回声定位咔哒声进行三维定位，以刻画其声学行为与潜水行为特征。基于上述数据，本研究构建了基于线索的蒙特卡洛模拟，以估算近海底单传感器高频声学记录包的检测概率。此外，本研究采用基于试验的方法，以部署于该站点的单通道传感器的探测距离为变量，估算其检测概率。研究结果显示不同喙鲸物种间存在显著差异。柯氏喙鲸（Ziphius cavirostris）在觅食潜水过程中的鸣唱时长更长（共记录24次潜水，平均时长20.5分钟，时长范围7~42分钟），相较于布氏中喙鲸（Mesoplodon densirostris，共记录2次潜水，平均13.6分钟，范围11~16分钟）与热尔韦斯喙鲸（Mesoplodon europaeus，共记录24次潜水，平均12.7分钟，范围7~19分钟）更久。不同物种的最大潜水深度亦存在差异，部分柯氏喙鲸可在海底或近海底区域觅食。同一物种的下潜与上升速率较为接近，但不同物种间存在显著差异：柯氏喙鲸的下潜/上升速率分别为1.34/1.40 m/s，热尔韦斯喙鲸则为1.15/1.19 m/s。柯氏喙鲸的源级与宽带指向性指数估算结果分别为225 dBpp（参考值：1 μPa·m）与26 dB，热尔韦斯喙鲸则分别为218 dBpp（参考值：1 μPa·m）与20 dB。由于有效数据量有限，无法获取布氏中喙鲸的相关估算结果。无论是基于蒙特卡洛的模拟还是基于试验的方法，检测概率均随探测距离的增加而急剧下降，这反映出喙鲸回声定位咔哒声具有极强的指向性波束特征。