NMML Small Cetacean (coastal) Aerial Survey 1999, Gulf of Alaska

The National Marine Mammal Laboratory (NMML) conducted an aerial survey for small cetaceans from 5 June to 4 July 1999 in Bristol Bay and along southwestern Alaska Peninsula (out to the 1829 m (1000 fm) depth contour). A total of 8,522 km were surveyed in a Dehavilland Twin Otter at 152.5 m (500 ft) altitude and 185 km/hr (100 kts). Two overlapping sawtooth lines were designed along the coastline of Bristol Bay. Both sides of each sawtooth were approximately 37 km with a 46 km base. Large bays were also included in the survey. Primary observers searched through bubble windows on the left and right sides of the aircraft and reported sightings to a computer operator. To estimate a perception bias correction factor for this study, an independent observer was added at a belly window position to determine the number of animals in the immediate vicinity of the trackline that were missed by the primary observers. There were 215 sightings of harbor porpoise (260 individuals), 12 Dall's porpoise (24 individuals), and 16 Pacific whitesided dolphins (170 individuals) while surveying tracklines. Additional cetacean sightings included 12 gray whales (13 individuals), 18 humpback whales (29 individuals), 8 minke whales (13 individuals), and 3 killer whales (11 individuals).美国国家海洋哺乳动物实验室（National Marine Mammal Laboratory, NMML）于1999年6月5日至7月4日，在布里斯托尔湾及阿拉斯加西南半岛沿岸（延伸至1829米（1000英寻）等深线区域）开展了小型鲸类航空调查。本次调查使用德哈维兰双水獭（Dehavilland Twin Otter）型飞机，以152.5米（500英尺）的飞行高度、185公里/小时（100节）的航速完成了总计8522公里的航程调查。研究团队沿布里斯托尔湾海岸线设计了两条重叠的锯齿状航线，每条锯齿的两侧线段长约37公里，基线长46公里，同时调查范围亦涵盖了大型海湾区域。主观察员透过飞机左右两侧的气泡观测窗开展搜寻，并将目击信息上报给计算机操作员。为估算本次研究的感知偏差校正系数，团队在飞机腹部观测窗增设了一名独立观察员，用于统计主观察员遗漏的、位于航线附近区域的鲸类个体数量。本次航线调查期间，共记录港湾鼠海豚（harbor porpoise）215次目击事件，涉及个体260头；达尔鼠海豚（Dall's porpoise）12次目击，涉及个体24头；太平洋白侧海豚（Pacific white-sided dolphin）16次目击，涉及个体170头。此外还记录到其他鲸类目击事件：灰鲸（gray whale）12次（13头）、座头鲸（humpback whale）18次（29头）、小须鲸（minke whale）8次（13头）以及虎鲸（killer whale）3次（11头）。