NMML Harbor Porpoise Aerial Survey, SE Alaska, Replicate 2, 1993

On 1 to 26 June 1993, as part of a larger study, Alaska harbor
porpoise (Phocoena phocoena) abundance was investigated during an aerial survey
from Prince William Sound to Dixon Entrance. Employing a Twin Otter as the
survey platform, the second of three identical saw-tooth tracklines was flown
at an altitude of 152.2 m (500ft) and at an airspeed of 100 kn. Line-transect
methodology was used, and only those observations made during optimal
conditions were analyzed. Density of harbor porpoises was calculated using line
transect estimates based on perpendicular distances of sightings to the cruise
track of the airplane. On average, porpoise group size and density from Prince
William Sound to Dixon Entrance was 1.22 (SE = .04) and 4.02 groups/100 km^2
(SE=7.42).

1993年6月1日至26日，作为一项大型研究的组成部分，研究人员开展航空调查以估算阿拉斯加港湾鼠海豚（Phocoena phocoena）的种群丰度，调查范围覆盖从威廉王子湾至迪克森海峡的海域。本次调查以双水獭（Twin Otter）飞机作为观测平台，共规划三条完全一致的锯齿状测线，本次飞行执行的是其中第二条测线，飞行高度为152.2米（500英尺），空速为100节（kn）。调查采用线样调查法（Line-transect methodology），仅对最优观测条件下获取的目击记录进行分析。港湾鼠海豚的种群密度通过线样估计法计算得出，估算依据为目击位置至飞机巡航航线的垂直距离。在本次调查覆盖的威廉王子湾至迪克森海峡海域内，港湾鼠海豚的平均群规模为1.22（标准误Standard Error, SE=0.04），平均种群密度为4.02群/100平方千米（SE=7.42）。