<div><p>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.</p>
<p>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.</p>
<p>Tide times on dates of aerial surveys are as follows:<br /><b>Date Tide Station Tide Time Tide Height (ft)</b><br />
07/17/08 Port Townsend 10:12 -1.7<br />
07/18/08 Port Townsend 10:49 -1.8<br />
07/18/08 Seattle 11:48 -1.6<br />
07/31/08 Port Townsend 09:44 -2.6<br />
07/31/08 Seattle 10:39 -2.9<br />
08/01/08 Port Townsend 10:32 -2.4<br />
08/14/08 Port Townsend 09:14 -0.9<br />
08/15/08 Port Townsend 09:52 -1.0</p>
<p><b>References:</b><br /><b>Jeffries</b> 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 <a href="http://wdfw.wa.gov/publications/00431/" target="_blank">Washington Department of Fish and Wildlife</a>.<br /><b>Huber</b> HR, Jeffries SJ, Brown RF, DeLong RL, Van Blaricom G (2001) Correcting aerial survey counts of harbor seals (<i>Phoca vitulina richardsi</i>) in Washington and Oregon. Marine Mammal Science 17:276-293. DOI: <a target="_blank" href="https://dx.doi.org/10.1111/j.1748-7692.2001.tb01271.x">10.1111/j.1748-7692.2001.tb01271.x</a></p></div>
Visual estimates of seal abundance from 2008 aerial surveys of the Salish Sea.
<div><p>Number of seals counted during several aerial surveys of the Salish Sea during July and August of 2008. Data are also available from <a href="http://osprey.bco-dmo.org/dataset.cfm?id=14099&flag=view">2007 surveys</a>.</p>
<p><b>Related publications:</b> (Both available from <a href="http://biol.wwu.edu/mbel/?page=papers" target="_blank">Alejandro Acevedo's lab website</a>.)<br /><b>Howard</b>, S. 2009. Seasonal energy budgets to model energy use and prey consumption in harbor seals (<i>Phoca vitulina</i>) in the San Juan Islands, WA. MSc thesis, Department of Biology, Western Washington University, Bellingham, WA.<br /><b>Hardee</b>, S. 2008. Movements and home ranges of harbor seals (<i>Phoca vitulina</i>) in the Georgia Basin: implications for marine reservinland waters of the Pacific Northwest. MSc thesis, Department of Biology, Western Washington University, Bellingham, WA.</p></div>
seal_counts_2008
<div><p>The estimation of seal population size based on haul-out counts requires a correction factor to account for seals in the water at the time of the survey (Huber et al. 2001, Jeffries et al. 2003), however, correction factors have NOT been applied to these data.</p>
<p><b>BCO-DMO made the following edits to the dataset:</b><br />
- Blanks and 'NA' were replaced with 'nd' to indicate 'no data';<br />
- Parameter names were modified to conform with BCO-DMO conventions;<br />
- day, month, and year were separated from original date column;<br />
- Abbreviated species names were replaced with the full species names;<br />
- Corrected typos in the year column from '2009' to '2008';<br />
- lat and lon were added based on the site_code (2007 site_codes are the same locations as 2008).</p></div>
3707
seal_counts_2008
2012-08-30T14:58:24-04:00
2012-08-30T14:58:24-04:00
2023-07-07T16:10:26-04:00
urn:bcodmo:dataset:3707
Visual estimates of seal abundance from aerial surveys conducted by a Cessna-185 in the San Juan Islands, Salish Sea in 2008 (Seal_response_to_prey project)
false
Acevedo-Gutierrez, A., Bromaghin, J. F., Jeffries, S. J., Kennish, J. M., Lance, M. M., Levin, P. S. (2012) Visual estimates of seal abundance from aerial surveys conducted by a Cessna-185 in the San Juan Islands, Salish Sea in 2008 (Seal_response_to_prey project). Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 16 Nov 2012) Version Date 2012-11-16 [if applicable, indicate subset used]. http://lod.bco-dmo.org/id/dataset/3707 [access date]
true
16 Nov 2012
false
2012-11-16
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