Gray whale visual sightings from shore 2014-2015

Original provider:
Regina A. Guazzo, Scripps Institution of Oceanography

Dataset credits:
National Oceanic and Atmospheric Administration, Southwest Fisheries
Science Center

Abstract:
During the eastern North Pacific gray whale 2014–2015 southbound
migration, acoustic call recordings, infrared blow detections, and visual
sightings were combined to estimate cue rates, needed to convert
detections into abundance. The gray whale M3 acoustic call rate was 2.3–24
calls/whale/day with an average of 7.5 calls/whale/day over the entire
migration (southbound and northbound) and showed a positive trend from
30 December–13 February. The infrared camera blow rate averaged 49
blows/whale/hour over 5–8 January. With a call rate model, we estimated
that 4,340 gray whales migrated south before visual observations began on
30 December, which is 2,829 more gray whales than used in the visual
abundance estimate. This finding highlights the usefulness of cue rates to
increase precision in abundance estimates. We suggest that visual
observers increase their survey effort to all of December to verify gray
whale abundance corrections. Probability of detection of a whale blow by
the infrared camera was the same at night as during the day. However,
probability of detection decreased beyond 2.1 km offshore, whereas visual
sightings revealed consistent whale densities up to 3 km offshore. We
suggest that future infrared camera surveys use multiple cameras
optimized for different ranges offshore.

原始提供者：
Regina A. Guazzo，斯克里普斯海洋研究所

数据集致谢：
美国国家海洋和大气管理局（National Oceanic and Atmospheric Administration）西南渔业科学中心

摘要：
在2014–2015年东太平洋灰鲸南徙期间，研究人员结合声学叫声记录、红外喷气探测与目视观测数据，估算了将探测结果转化为种群数量所需的信号率（cue rate）。灰鲸M3声学叫声率为2.3–24次/鲸/日，全迁徙周期（南徙与北徙）平均为7.5次/鲸/日，且在12月30日至2月13日期间呈上升趋势。1月5日至8日期间，红外相机探测到的喷气率平均为49次/鲸/小时。通过叫声率模型估算，在12月30日目视观测开始前，已有4340头灰鲸完成南徙，较目视种群数量估算值多出2829头。该发现凸显了信号率在提升种群数量估算精度方面的价值。研究建议目视观测人员将调查范围扩展至整个12月，以验证灰鲸种群数量的校正结果。红外相机探测鲸喷气的概率在昼夜之间无显著差异，但离岸距离超过2.1千米时探测概率下降；而目视观测显示，离岸3千米范围内的鲸密度保持稳定。因此建议未来的红外相机调查采用针对不同离岸距离优化的多相机系统。