Disappearance and Return of Harbor Porpoise to Puget Sound: 20 Year Pattern Revealed from Winter Aerial Surveys

2016 2 | P a g e Disappearance and Return of Harbor Porpoise to Puget Sound: 20 Year Pattern Revealed from Winter Aerial Surveys Summary Harbor porpoise were a common year-round resident in the Puget Sound in the 1940s, but by the 1970s, they had disappeared from the Sound, and their numbers were greatly reduced in the Straits of Georgia and Juan de Fuca, and around the San Juan Islands. [...] While it is not designed as a dedicated marine mammal survey, because of the consistent survey methodology throughout the survey area, and that all marine mammal observations were recorded, this 20-year dataset provides a record of increasing harbor porpoise numbers in the northern portion of the survey area in the early years, followed by their expansion into the waters of the Puget Sound. [...] We are also very grateful to Don for his constant support in the safety of the crew by supporting all of the trainings identified and requested, as well as the acquisition of all safety equipment identified to ensure the safety of the flight crew. [...] Reports during the 1960s, 1970s and 1980s documented Dall’s porpoise presence in the inland waters during all months of the year, with the center of abundance in the Strait of Juan de Fuca, including animals sighted as far east as Rosario Strait, and down into the central Puget Sound Basin, with occasional sightings into the south Puget Sound. [...] Discussion The results of these aerial surveys, over a period of two decades, document both increasing trends followed by stabilization of the harbor porpoise in the waters of the Strait of Juan de Fuca and Washington Sound, and their expansion into the previously abandoned waters of the Puget Sound and the waters of the Eastern Strait of Georgia, along with the concurrent decline of Dall’s porpoi.