Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, 92093-0205, United States of America.
Naval Information Warfare Center Pacific, San Diego, California, 92152-5001, United States of America.
Sci Rep. 2019 Aug 30;9(1):12617. doi: 10.1038/s41598-019-49115-y.
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 acoustic call rate ranged from 2.3-24 calls/whale/day during the peak of the southbound migration with an average of 7.5 calls/whale/day over both the southbound and northbound migrations. The average daily calling rate increased between 30 December-13 February. 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 estimate, and would add approximately 10% to the abundance estimate. We suggest that visual observers increase their survey effort to all of December to document gray whale presence. The infrared camera blow rate averaged 49 blows/whale/hour over 5-8 January. 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 optimised for different ranges offshore.
在 2014-2015 年度东太平洋灰鲸南下洄游期间，我们将声学呼叫记录、红外喷气检测和目视观测相结合，以估算转换检测结果为数量所需的线索率。灰鲸的声学呼叫率在南下洄游高峰期为 2.3-24 次/鲸/天，在南下和北上洄游过程中平均为 7.5 次/鲸/天。每日呼叫率在 12 月 30 日至 2 月 13 日之间增加。根据呼叫率模型，我们估计在 12 月 30 日开始目视观测之前，有 4340 头灰鲸向南洄游，比目视估计中使用的灰鲸数量多 2829 头，这将使数量估计增加约 10%。我们建议目视观测者增加 12 月的观测力度，以记录灰鲸的存在。红外摄像机喷气率在 1 月 5 日至 8 日期间平均为 49 次/鲸/小时。红外摄像机探测到鲸鱼喷气的概率在夜间与白天相同。然而，在离岸 2.1 公里以外，探测概率下降，而目视观测显示，在离岸 3 公里的范围内，鲸鱼的密度一直保持稳定。我们建议未来的红外摄像机调查使用多个摄像机，优化不同离岸距离的观测。
