Dataset: seal_counts_2008
Deployment: Aerial_Survey_2008_SRtP

Following protocol from Jeffries et al. (2003), with collaboration from the Washington Department of Fish and Wildlife, surveys were flown in a Cessna 185 at 200 to 300 m, moving at 90 kt, on two or three consecutive days during moderately low tides. Flights were made over the region moving with the tide, to cover the entire area within +/- 2 h from low tide. Visual counts were taken on sites with < 25 seals and digital photographs and visual counts were taken concurrently at sites with > 25 animals, using a Nikon D100 with a 200 mm lens. The time was documented on the survey log for all haul-out counts, haul-out estimates and photographs. Surveys were conducted under permit 782-1702 awarded to the Washington Department of Fish and Wildlife by the Office of Protected Resources.

Selection of flight times was not only dependent on tidal conditions but also on time of day. If one chooses tidal heights that are extremely low, there is a risk that the survey underestimates the number of seals in the region because normal haul-out sites may be inaccessible (Jeffries, pers. comm.). Additionally, fog may become problematic for flying if the tide window, especially in August, is too early in the morning. These factors were taken into account when selecting the survey dates.

Tide times on dates of aerial surveys are as follows:
Date       Tide Station        Tide Time     Tide Height (ft)
07/17/08  Port Townsend     10:12             -1.7
07/18/08  Port Townsend     10:49             -1.8
07/18/08  Seattle                  11:48            -1.6
07/31/08  Port Townsend      09:44            -2.6
07/31/08  Seattle                  10:39            -2.9
08/01/08  Port Townsend      10:32            -2.4
08/14/08  Port Townsend      09:14            -0.9
08/15/08  Port Townsend      09:52            -1.0

References:
Jeffries SJ, Huber HR, Calambokidis J, Laake J (2003) Trends and status of harbor seals in Washington State: 1978-1999. Journal of Wildlife Management 67:208-219. Available online from Washington Department of Fish and Wildlife.
Huber HR, Jeffries SJ, Brown RF, DeLong RL, Van Blaricom G (2001) Correcting aerial survey counts of harbor seals (Phoca vitulina richardsi) in Washington and Oregon. Marine Mammal Science 17:276-293. DOI: 10.1111/j.1748-7692.2001.tb01271.x